Re: Data available on socket?
Jan Danielsson a écrit : > Hello all, > >How do I find out if a blocking socket has data available [for > reading] on it? > > I assume I could do something like this: > > tmp = self.read(1, socket.MSG_PEEK) > if len(tmp) > 0: ># Data available > >But is there a better way? A call which specifically checks if data > is available? Hello, You might want to use select.select. See http://effbot.org/librarybook/select.htm for an example with sockets. Nicolas. -- http://mail.python.org/mailman/listinfo/python-list
clicking on turtle
I have a problem with the standard "turtle" module. When a turtle has
a custom shape of type "compound", it doesn't seem to respond to click
events. No problem with polygon shapes.
Running python 3.2.3, turtle version 1.1b on Windows XP.
Here is my test file:
##
import turtle
square = ((0,0),(0,20),(20,20),(20,0))
turtle.addshape("sq1", square) # sq1 = polygon shape
s = turtle.Shape("compound")
s.addcomponent(square, "red")
turtle.addshape("sq2", s) # sq2 = compound shape
t1 = turtle.Turtle(shape="sq1")
t2 = turtle.Turtle(shape="sq2")
t2.fd(20) # set the turtles side by side
def click(x,y): print("click at",x,y)
t1.onclick(click)
t2.onclick(click)
turtle.mainloop()
##
When I run this and click on the black square (i.e. t1), the message
"click at..." gets printed on the console. When I click on the red
square (i.e. t2), nothing happens.
Bug or feature?
--Nicolas
--
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Re: Migrate from Access 2010 / VBA
* Wolfgang Keller [2012-11-25 20:48 +0100]: I am the lone developer of db apps at a company of 350+ employees. Everything is done in MS Access 2010 and VBA. I'm frustrated with the limitations of this platform and have been considering switching to Python. I've been experimenting with the language for a year or so, and feel comfortable with the basics. I am concerned that I'll have a hard time replacing the access form and report designers. I've worked a little with TKinter, but it's a far cry from the GUI designer in Access. The list of Python frameworks for rapid development of desktop (i.e. non-Web) database applications currently contains: using PyQt (& Sqlalchemy): Pypapi: www.pypapi.org Camelot: www.python-camelot.com Qtalchemy: www.qtalchemy.org using PyGTK: Sqlkit: sqlkit.argolinux.org (also uses Sqlalchemy) Kiwi: www.async.com.br/projects/kiwi using wxPython: Dabo: www.dabodev.com Defis: sourceforge.net/projects/defis (Russian only) GNUe: www.gnuenterprise.org Pypapi, Camelot, Sqlkit and Dabo seem to be the most active and best documented/supported ones. I'd like to add to the list Tryton http://www.tryton.org/ Which framework can be used to create a business application without even using the already existing modules (one of our customer uses only the 'party' modules in order to manage insurance products, the GNU Health (http://www.gnuhealth.org/) project uses more official modules to create their HIS software). Reporting is done through relatorio (http://relatorio.openhex.org/), which uses ODF templates to generate ODF reports (or other format thanks to unoconv) the client is written in GTk (we're writing one in JavaScript right now (and I miss python badly)). -- (°> Nicolas Évrard ( ) Liège `¯ signature.asc Description: Digital signature -- http://mail.python.org/mailman/listinfo/python-list
[winreg] How to access "(Default)" key value?
Hello, I am encountering an issue with winreg, I can't figure out how to read the "(Default)" of a registry value ``` def get_chrome_version() -> str: with winreg.ConnectRegistry(None, winreg.HKEY_CURRENT_USER) as registry: with winreg.OpenKeyEx(registry, r"Software\Microsoft\Windows\CurrentVersion\App Paths\chrome.exe", access=winreg.KEY_READ) as key: value, _ = winreg.QueryValueEx(key, "(default)") return value ``` Taking the example above it raises a FileNotFoundError : ``` Traceback (most recent call last): File "C:/Users/noulo/dev/py/chromedriver_dl/main.py", line 14, in get_chrome_version value, _ = winreg.QueryValueEx(key, "(default)") FileNotFoundError: [WinError 2] The system cannot find the file specified ``` (Trying "Path" instead of "(Default)" works) Although the value definitely exists as shown by Powershell ``` Get-Item -Path "HKCU:/Software/Microsoft/Windows/CurrentVersion/App Paths/chrome.exe" | Select-Object -ExpandProperty Property ``` Returns : ``` (default) Path ``` Is this a bug I should report, or if not, what is the way, using winreg, to access the "(Default)" value of a key? Regards, Nicolas FORMICHELLA -- https://mail.python.org/mailman/listinfo/python-list
Typing on child class' methods of a Generic base class
Hello,
I am wondering about a situation involving typing, Generic and a child
class.
The documentation about "user-defined generic types"[1] says that I can
fix some types on a child class (class MyDict(Mapping[str, T]):) but
doesn't say much about the signature of the methods I need to
implement/override on that child class.
Should I keep the TypeVar and remember that I fixed the type(alternative
1) or change the signature of the method to replace the TypeVar by the
type I set (alternative 2)?
Mypy seems to prefer the second alternative but changing the signature
feels wrong to me for some reason. That's why I'm asking :-)
Below is a small example to illustrate:
from abc import ABCMeta, abstractmethod
from typing import TypeVar, Generic
T = TypeVar("T")
class Base(Generic[T], metaclass=ABCMeta):
"""A base class."""
@abstractmethod
def _private_method(self, an_arg: T) -> T:
...
def public_method(self, an_arg: T) -> T:
from_private_method = self._private_method(an_arg)
return from_private_method
class Alternative1(Base[int]):
def _private_method(self, an_arg: T) -> T: # I keep T
return 42
class Alternative2(Base[int]):
def _private_method(self, an_arg: int) -> int: # I replace T
return 42
Thanks,
--
Nicolas Haller
[1]:
https://docs.python.org/3/library/typing.html#user-defined-generic-types
--
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Re: Typing on child class' methods of a Generic base class
On 2022-03-10 12:31, Dieter Maurer wrote:
Nicolas Haller wrote at 2022-3-9 10:53 -0500:
...
The documentation about "user-defined generic types"[1] says that I can
fix some types on a child class (class MyDict(Mapping[str, T]):) but
doesn't say much about the signature of the methods I need to
implement/override on that child class.
I have the fealing that this is a case of (generic type) "specialization".
In this setup, `Mapping` would be a generic type with two type
variables `K` (the key type) and `V` (the value type).
The signatures of its methods would use those type variables.
In your example, you specialize the key type to `str` (and
leave the value type generic). The signatures of the methods
would automatically follow this specialization -- without the need
to do anything.
If I understand correctly, you're saying I should use the first
alternative by keeping the signature as it is in the base class:
---
T = TypeVar("T")
class Base(Generic[T], metaclass=ABCMeta):
"""A base class."""
@abstractmethod
def _private_method(self, an_arg: T) -> T:
...
def public_method(self, an_arg: T) -> T:
from_private_method = self._private_method(an_arg)
return from_private_method
class Alternative1(Base[int]):
def _private_method(self, an_arg: T) -> T: # I keep T
return 42
---
The problem with it is that mypy doesn´t seem quite happy with it:
./scratch.py:22: error: Incompatible return value type (got "int",
expected "T")
Do you think this is error is incorrect? If so, I can open an issue with
mypy.
Thanks,
--
Nicolas
--
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Pretty printing dicts with compact=True
Is there a reason why the 'compact' parameter is ignored when pretty
printing a dict? For example:
pprint({x: x for x in range(15)}, compact=True)
would be be printed in 15 lines while it could fit on 2.
Is this a bug or was this decided on purpose?
Thank you!
--
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Re: Pretty printing dicts with compact=True
To me it also seems to be the most sensible behaviour, since
dictionaries with their keys and values are different from most other
sequences.
You've got a point but
1. That goes against the compact=True expected behaviour
2. Small dicts (e.g. /{x: x for x in range(5)}/) are still printed on a
single line (regardless of the compact parameter), so I don't believe
that was the rationale behind this behaviour.
On 9/11/18 1:05 PM, Max Zettlmeißl wrote:
On Tue, Sep 11, 2018 at 1:58 PM, Nicolas Hug wrote:
pprint({x: x for x in range(15)}, compact=True)
would be be printed in 15 lines while it could fit on 2.
Is this a bug or was this decided on purpose?
It is on purpose as can be seen in the code for pprint [1], which
calls _format [2], which in the case of a dictionary calls
_pprint_dict [3], which ultimately calls _format_dict_items [4].
(which does not use compact or rather _compact)
To me it also seems to be the most sensible behaviour, since
dictionaries with their keys and values are different from most other
sequences. In a dictionary the relation between keys and values is the
most important one and reading a dictionary certainly is easier if
each key value pair has a line of it's own. (Especially if the keys
and values vary a lot in their lengths.)
[1]
https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/pprint.py#L138
[2]
https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/pprint.py#L154
[3]
https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/pprint.py#L180
[4]
https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/pprint.py#L333
--
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Re: SOAP and Zeep
* Ethan Furman [2016-07-29 19:54 +0200]: Greetings! I may have a need in the immediate future to work with SOAP and WSDL services, and a quick search turned up Zeep (http://docs.python-zeep.org/en/latest/) -- does anyone have any experience with it? Or any other libraries that can be recommended? We used zeep to communicate with SOAP webservices. We choose it over suds because it supports python3. I also happen to have a bug, and the maintainer quickly accepted my patch, so according to me it's a good choice. -- (°> Nicolas Évrard ( ) Liège `¯ -- https://mail.python.org/mailman/listinfo/python-list
my matplotlib realtime plot doesn't show the line between the points
hi guys, i need help because my matplotlib realtime plot doesn't show the line
between the points.
even if i right '.k-'
thit plot is display in a qwidget in an other code
wirdely that if i put bar it actualy working.
the real time data come from an arduino sensor
that the shape of the data i have to plot:
ser_bytes = ser.readline()
value = float(ser_bytes[0:len(ser_bytes)-2].decode("utf-8"))
that is my code:
class MplWidget(QWidget ):
def __init__( self, parent = None):
QWidget.__init__(self, parent)
self.canvas = FigureCanvas(Figure())
vertical_layout = QVBoxLayout()
vertical_layout.addWidget(self.canvas)
self.canvas.axes = self.canvas.figure.add_subplot(1,1,1)
self.canvas.axes.set_ylim(0,90)
self.canvas.axes.set_xlim(0,100)
self.setLayout(vertical_layout)
def update_graph(self, value):
y = list()
x = list()
y.append(value)
x.append(self.i)
self.i += 1
self.MplWidget.canvas.axes.set_xlim(left=max(0, self.i-40), right=
self.i+60)
self.MplWidget.canvas.axes.bar(x, y,)#'.k-')
self.MplWidget.canvas.axes.set_title('pull')
self.MplWidget.canvas.draw()
thanks for help!
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Re: my matplotlib realtime plot doesn't show the line between the points
sorry that the real piece of code
self.MplWidget.canvas.axes.set_xlim(left=max(0, self.i-40), right=
self.i+60)
self.MplWidget.canvas.axes.plot(x, y,'.k-')
self.MplWidget.canvas.axes.set_title('pull')
self.MplWidget.canvas.draw()
--
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Continuous system simulation in Python
Hello, I'm looking for any work/paper/ressource about continuous system simulation using Python or any similar object oriented languages (or even UML theory !). I'm aware of SimPy for discrete event simulation, but I haven't found any work about continuous system. I would like to develop a generic continous system simulator, and so would be eager to join any open source effort on the subject. For instance, it would be useful for modelling an airplane with all the dynamics (flight simulator). Python is my language of choice because of the keyword 'generic'. Being an object oriented dynamic language, it's perfect for such a task. Unfortunately I'm a novice when it comes to object oriented design and development, so I would prefer to start from something already existent instead of starting from scratch. If you had any idea on the subject, I would be really glad to discuss it with you. Thanks in advance, P.S. : for email, replace nowhere by yahoo -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
Hello Phil, Yes I have considered Octave. In fact I'm already using Matlab and decided to 'reject' it for Python + Numeric/numarray + SciPy because I think you could do more in Python and in more simple ways. Problem is that neither Octave, Matlab and Python offer today a framework to build continuous system simulator (in fact Matlab with Simulink and SimMechanics, do propose, but I was not convinced at all). Regards, *** REPLY SEPARATOR *** On 7 Oct 2005 11:00:54 -0700, [EMAIL PROTECTED] wrote : > Nicholas, > > Have you looked at Octave? It is not Python, but I believe it can talk > to Python. > Octave is comparable to Matlab for many things, including having ODE > solvers. I have successfully used it to model and simulate simple > systems. Complex system would be easy to model as well, provided that > you model your dynamic elements with (systems of) differential > equations. > -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
On Thu, 06 Oct 2005 22:30:00 -0700, Robert Kern <[EMAIL PROTECTED]> wrote : > Dennis Lee Bieber wrote: > > On Fri, 7 Oct 2005 01:12:22 +0200, Nicolas Pernetty > > <[EMAIL PROTECTED]> declaimed the following in > > comp.lang.python: > > > > > I'm aware of SimPy for discrete event simulation, but I haven't > > > found any work about continuous system. > > > I would like to develop a generic continous system simulator, and > > > so would be eager to join any open source effort on the subject. > > > > > >For instance, it would be useful for modelling an airplane with all > > > the dynamics (flight simulator). > > > > Unless that flight simulator is running on some big ugly ANALOG > > computer (the ones that used rheostats, transformers, and > > amplifiers), they all are really using discrete time intervals and > > computing values at those time points. Such computation may require > > integration of continuous functions from previous time step to > > current time step. > > I think Nicolas means "(discrete event) simulation" as opposed to > "discrete (event simulation)" and "(continuous system) simulation" as > opposed to "continuous (system simulation)". The methods used in SimPy > to model (discrete events) don't apply terribly well to simulating > many (continuous systems) like airplane dynamics. For example, an ODE > integrator would probably want to adaptively select its timesteps as > opposed to laying out a uniform discretization upfront. > Yes you are absolutely right. That's what I wanted to mean. Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
Thanks, but what is really difficult is not to understand how to design the program which solve a specific problem but to design a generic framework for solving all these kinds of problem. And in a simple enough way for basic programmers (but good scientists !) to handle it. *** REPLY SEPARATOR *** On 6 Oct 2005 17:04:01 -0700, "hrh1818" <[EMAIL PROTECTED]> wrote : > A good starting point is the book "Python Scripting for Computational > Science" by Hans Petter Langtangen. The book covers topics that go > from simulating second order mechanical systems to solving partial > differentail equations. > > Howard > > Nicolas Pernetty wrote: > > Hello, > > > > I'm looking for any work/paper/ressource about continuous system > > simulation using Python or any similar object oriented languages (or > > even UML theory !). > > > > I'm aware of SimPy for discrete event simulation, but I haven't > > found any work about continuous system. > > I would like to develop a generic continous system simulator, and so > > would be eager to join any open source effort on the subject. > > > > For instance, it would be useful for modelling an airplane with all > > the dynamics (flight simulator). > > > > Python is my language of choice because of the keyword 'generic'. > > Being an object oriented dynamic language, it's perfect for such a > > task. Unfortunately I'm a novice when it comes to object oriented > > design and development, so I would prefer to start from something > > already existent instead of starting from scratch. > > > > If you had any idea on the subject, I would be really glad to > > discuss it with you. > > > > Thanks in advance, > > > > P.S. : for email, replace nowhere by yahoo > -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
Simulink is well fitted for small simulators, but when you run into big projects, I find many shortcomings appears which made the whole thing next to unusable for our kind of projects. That's why I'm interested in Python by the way, it is not a simple clone like Scilab/Scicos. It is a real language which bring its own advantages, and its own shortcomings, which I find well suited for our activity. If you want, I can send you a paper I wrote last year, detailing all Simulink shortcomings. I doubt that this mailing list is interested in such things...(and it's in French...). Concerning Scilab/Scicos, I'm not really interested in a technology primarily developed (INRIA and ENSPC) and used by France. Python and all its libraries and communities are so much more dynamic ! And also I've heard that Scilab was developed in Fortran in a way which make it rigid and that the sources are poorly documented, not a good sign for an open source software (and Scilab isn't 'Free' for the FSF). Regards, *** REPLY SEPARATOR *** On 8 Oct 2005 11:06:25 -0700, "Sébastien Boisgérault" <[EMAIL PROTECTED]> wrote : > > Simulink is a framework widely used by the control engineers ... > It is not *perfect* but the ODEs piece is probably the best > part of the simulator. Why were you not convinced ? > > You may also have a look at Scicos and Ptolemy II. These > simulators are open-source ... but not based on Python. > > Cheers, > > SB > > > > > > Nicolas Pernetty a écrit : > > > Hello Phil, > > > > Yes I have considered Octave. In fact I'm already using Matlab and > > decided to 'reject' it for Python + Numeric/numarray + SciPy because > > I think you could do more in Python and in more simple ways. > > > > Problem is that neither Octave, Matlab and Python offer today a > > framework to build continuous system simulator (in fact Matlab with > > Simulink and SimMechanics, do propose, but I was not convinced at > > all). > > > > Regards, > > > > *** REPLY SEPARATOR *** > > > > On 7 Oct 2005 11:00:54 -0700, [EMAIL PROTECTED] wrote : > > > > > Nicholas, > > > > > > Have you looked at Octave? It is not Python, but I believe it can > > > talk to Python. > > > Octave is comparable to Matlab for many things, including having > > > ODE solvers. I have successfully used it to model and simulate > > > simple systems. Complex system would be easy to model as well, > > > provided that you model your dynamic elements with (systems of) > > > differential equations. > > > > -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
Hello Phil, I'm currently looking to see if I can build upon SimPy, thus making it an hybrid system simulator. That would be a great step for the community. Main difficulty would be to build a framework which isn't clumsy, like you said. I have close to no experience in Python and object oriented development, but I'm fairly advanced in C and procedural development, and of course in continuous sytem simulator. I'll keep you informed of my investigations... I've downloaded your zip files, but unfortunately I have no access to Windows. Are you able to send me only the sources ? Thanks in advance, *** REPLY SEPARATOR *** On 8 Oct 2005 21:36:05 -0700, [EMAIL PROTECTED] wrote : > Nicholas, > > I have a particular interest in this subject as well. I've also used > the Python/Scipy combination, and it is a tantalizing combination, but > I found it to be a bit more clumsy than I'd like. Plus, my need for > continuous-time simulation is not as great as it has been in the past. > > That said, I've been down this path before (see > http://custom.lab.unb.br/pub/asme/DYNAMICS/BUFORD1.zip), and I would > be interested in helping to develop something. I agree that Python > would be a great foundation to build upon. > -- http://mail.python.org/mailman/listinfo/python-list
Re: Continuous system simulation in Python
> I am aware of some shortcomings and design flaws of Simulink, > especially in the code generation area. I am interested by > your paper nonetheless, please send me copy. Ok no problem. Let me just a few days to strip any irrelevant data on it... > However, Simulink is used by many people on a day-to-day basis > in the context of big, industrial projects. The claim that it > is "next to unusable" is, in my book, an overstatement ... Well the exact sentence is "next to unusable for our kind of projects". You'll see the details on the paper, but I'm not joking. For instance, under Simulink, our model is so big (well not so, but too big for Simulink obviously), that you may have a loss of up to 40x in performance compared to the model in C (how to optimize the Simulink model is a whole other subject in itself). So to make it usable, we have to use automatic code generation wich bring a whole new set of problems... BUT our work is *very* specific, and I'm not talking about Simulink in general. It may be perfect suited for others, it's just that for us it's far from perfect... > Scicos is not perfect either but you can hardly say that is > is a simple clone of Simulink. No time and space to go into > the details ... I wasn't in charge of evaluating Scilab/Scicos, so I can only talk about the conclusion : main motives to switch to Scilab/Scicos would be because it's free, that's all. Report said that next to almost everything Scilab/Scicos does, Matlab/Simulink can do, and more often than not, do it much better. So if you have a different report, I would be happy to read and transmit it... > Obviously, the python community is very dynamic, but how much > support will you get in the very specific topic of continuous > time systems simulation ? Well some people already offered me their help. But I believe that someone _has_ to begin alone some day... Otherwise people who work on continuous system simulation would never be interested in Python. That's the beauty of open source : do what you can, but do it ! and hope that someone else will come one day and use your work to build upon it. Step by step you will have something usable (in theory). > IMHO, an hybrid approach, such as the development of bridge > to include Python components into Simulink/Scicos/Ptolemy/ > Modelica/pick_your_favorite_simulator may grant you more > interest from the simulation community. I already know some bridges like pymat or mlabwrap and I agree that a way to include Python to Matlab/Simulink would be a great step. But : 1) I think that it's Mathworks job to do it, and if they don't want to do it, we'll never have a very good integration. 2) For our kind of projects and our kind of developers (mainly non-IT engineers), I'm very reluctant to introduce too many different technologies in a project. If we decided to go for Python, fine, let's do the entire thing in Python/C. If we decided to go for Simulink, fine, let's do the whole thing in Simulink/Matlab/C. Matlab, for algorithms, can do almost the same things than Python and sometimes much better, so if you have already Simulink (and so have the license) why go for Python and struggle to have a good integration ? Regards, > > Cheers, > > SB > > > > Nicolas Pernetty wrote: > > Simulink is well fitted for small simulators, but when you run into > > big projects, I find many shortcomings appears which made the whole > > thing next to unusable for our kind of projects. > > That's why I'm interested in Python by the way, it is not a simple > > clone like Scilab/Scicos. It is a real language which bring its own > > advantages, and its own shortcomings, which I find well suited for > > our activity. > > > > If you want, I can send you a paper I wrote last year, detailing all > > Simulink shortcomings. I doubt that this mailing list is interested > > in such things...(and it's in French...). > > Concerning Scilab/Scicos, I'm not really interested in a technology > > primarily developed (INRIA and ENSPC) and used by France. Python and > > all its libraries and communities are so much more dynamic ! > > And also I've heard that Scilab was developed in Fortran in a way > > which make it rigid and that the sources are poorly documented, not > > a good sign for an open source software (and Scilab isn't 'Free' for > > the FSF). > > > > Regards, > > > > > > *** REPLY SEPARATOR *** > > > > On 8 Oct 2005 11:06:25 -0700, "Sébastien Boisgérault" > > <[EMAIL PROTECTED]> wrote : > > > > > > > > Simulink is a framework widely used by the control engineers ... > > >
Re: Continuous system simulation in Python
I was implicitly referring to Python/C model for this. I'm aware that Python can be very slow on heavy computations (it's a _documented_ shortcoming), sometimes much slower than Simulink. I believe that no current technology can meet the needs of both rapid prototyping (for projects in their infancy) and performance (for projects in their industrial cycle). That's why, as it is _documented_ and _recommended_ on the Python website, I intend to first prototype with Python then slowly migrate some critical parts to C/C++ as we refine and stabilize the specs. Ideally, at the end of the project, we'll have the best of both worlds. Note that it's the first time that I try this, I may be a perfectly wrong approach for continuous system simulation... *** REPLY SEPARATOR *** On 10 Oct 2005 17:48:39 -0700, "hrh1818" <[EMAIL PROTECTED]> wrote : > In your simulator how much do you want Python to do? I ask this > because your subject title implies you want to write your simulation > code in Python but a simulator written entirely in Python would be > very slow. Python is an interpreted language and pure Python code is > not suitable for simulating big continuous systems. Hence to me it > appears you have two distinct proplems. One is developing a front end, > a user interface, that is easy to use. The other is either finding or > writing a good code compiler that wlll produce fast simulation code or > writing an interface to existing optimize simulation code. Although > most likely not suitable for your applicaion but a good example of > this type of program is Mathematica. It is written in two parts a user > interface and a kernel that does all of the high power math. > > Howard > > > Nicolas Pernetty wrote: > > > I am aware of some shortcomings and design flaws of Simulink, > > > especially in the code generation area. I am interested by > > > your paper nonetheless, please send me copy. > > > > Ok no problem. Let me just a few days to strip any irrelevant data > > on it... > > > > > However, Simulink is used by many people on a day-to-day basis > > > in the context of big, industrial projects. The claim that it > > > is "next to unusable" is, in my book, an overstatement ... > > > > Well the exact sentence is "next to unusable for our kind of > > projects". You'll see the details on the paper, but I'm not joking. > > For instance, under Simulink, our model is so big (well not so, but > > too big for Simulink obviously), that you may have a loss of up to > > 40x in performance compared to the model in C (how to optimize the > > Simulink model is a whole other subject in itself). So to make it > > usable, we have to use automatic code generation wich bring a whole > > new set of problems... BUT our work is *very* specific, and I'm not > > talking about Simulink in general. It may be perfect suited for > > others, it's just that for us it's far from perfect... > > > > > Scicos is not perfect either but you can hardly say that is > > > is a simple clone of Simulink. No time and space to go into > > > the details ... > > > > I wasn't in charge of evaluating Scilab/Scicos, so I can only talk > > about the conclusion : main motives to switch to Scilab/Scicos would > > be because it's free, that's all. Report said that next to almost > > everything Scilab/Scicos does, Matlab/Simulink can do, and more > > often than not, do it much better. > > So if you have a different report, I would be happy to read and > > transmit it... > > > > > Obviously, the python community is very dynamic, but how much > > > support will you get in the very specific topic of continuous > > > time systems simulation ? > > > > Well some people already offered me their help. But I believe > > that someone _has_ to begin alone some day... > > Otherwise people who work on continuous system simulation would > > never be interested in Python. > > > > That's the beauty of open source : do what you can, but do it ! and > > hope that someone else will come one day and use your work to build > > upon it. Step by step you will have something usable (in theory). > > > > > IMHO, an hybrid approach, such as the development of bridge > > > to include Python components into Simulink/Scicos/Ptolemy/ > > > Modelica/pick_your_favorite_simulator may grant you more > > > interest from the simulation community. > > > > I already know some bridges like pymat or mlabwrap and I agree that > > a way to include Python t
Numeric array equivalent of index ?
Hello, I'm trying to find a clear and fast equivalent to the index method of plain python list : >> a = [5,1,4,3,4] >> a.index(4) 2 I have to use it on a Numeric array, so the best I've come up with is (rather ugly I think) : >> from Numeric import array, equal, nonzero >> a = array([5,1,4,3,4]) >> nonzero(equal(a,4))[0] 2 Does someone know of a more Pythonic way ? Thanks, -- http://mail.python.org/mailman/listinfo/python-list
Examples of Python code compared to other languages
Hello,
I'm looking (without success so far) for code sources for common
problems in different languages, but especially Python, C, Fortran, Ada
and Matlab.
It would help people coming from other languages to understand the
'python way of thinking'.
Priority is clean code, performance is not an issue here because it
often leads to obscure code.
Ideally code for Python would extensively use the standard library
("don't reinvent the wheel").
I've already checked the following sites, but they were not suited for
what I'm looking for :
These ones are too focused on performance :
http://shootout.alioth.debian.org/
http://dada.perl.it/shootout/
This one don't include C or Fortran :
http://pleac.sourceforge.net/
This one is ok but rather limited :
http://www.kochandreas.com/home/language/lang.htm
If there is a site which regroup very good ('Pythonic') code examples
which make extensively use of standard library to resolve common
problems, I would be happy to help and try to contribute by giving the
equivalent in C code.
Regards,
--
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Re: Examples of Python code compared to other languages
On 29 Oct 2005 21:27:39 -0700, [EMAIL PROTECTED] wrote : > http://pleac.sourceforge.net/ probably is what you're looking for. It > shows how to to stuff from the perl cookbook in a plethora of other > languages, including Python. > > Kind regards Terji Petersen > Hello, As mentioned in the original message, this site is good but doesn't include C or Fortran. Of course I can try to contribute with C code... Thanks anyway, -- http://mail.python.org/mailman/listinfo/python-list
recursive function call
Hello, I have in my python script a function that look like this : def my_function(arg1, arg2, opt1=0, opt2=1, opt3=42): if type(arg1) is ListType: for a in arg1: my_function(a, arg2, opt1=opt1, opt2=opt2, opt3=opt3) return if type(arg2) is ListType: for a in arg2: my_function(arg1, a, opt1=opt1, opt2=opt2, opt3=opt3) return ... then here the real function code I'm new to python, so I was wondering if there is a better way to do that. The reason for a recursive function here is to be able to give lists for the first 2 args (I could as well use only a simple 'for' without a recursive call). The problem I have here, is that as I'm working on this script, I often change the prototype of the function, and each time I have to think about changing the recursive call too. Is there a way that I can do a recursive call and say something like "keep all the same arguments except this one" ? Thanks Nicolas -- http://n0x.org/ - [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: recursive function call
Peter Otten said: > Here is a non-recursive approach: > > def tolist(arg): >if isinstance(arg, list): >return arg >return [arg] > > def f(arg1, arg2, more_args): >for arg1 in tolist(arg1): >for arg2 in tolist(arg2): ># real code > > If it were my code I would omit the tolist() stuff and instead always > pass lists (or iterables) as the function's first two arguments. Hmm, that's right. After all it's not very useful to be able to give a single element, passing a list all the time is more simple. That's what I'll do. I got the idea of passing a list or a singe element because that's what they do in SCons, but in my case it's not really usefull. Thanks -- http://n0x.org/ - [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: option argument length
I don't think that's actually what you want to do. Yes arguments are not to be used directly as option arguments (otherwise why have option arguments anyways ;-) but each option argument is usually evaluated under the evaluation of the actual option and optparse will error on invalid use of the options you build. Why exactly do you think you need to find the number of optional arguments? Everytime I thought about the need for this kind of option parsing design I was able to find an easier way to achieve what I wanted to do. See "How optik handles errors" - http://optik.sourceforge.net/doc/1.5/tutorial.html If you really think you need to be doing this, you can modify the following function: def is_empty(options ):"""Returns True or False if an option is set or not. """values = options .__dict__.values()return (values == [None] * len(values)) On 12/4/05, Ritesh Raj Sarraf <[EMAIL PROTECTED]> wrote: -BEGIN PGP SIGNED MESSAGE-Hash: SHA1Hi,I'm using optparse module to parse all options and arguments.My program uses mostly "option arguments" hence my len(args) value is always zero. I need to check if the user has passed the correct number of "optionarguments". Something like:(options,args) = parser.parse_args()len(options) != 1 or len(options) > 2:print "Incorrect number of arguments passed." How do I accomplish it ?Regards,rrs- --Ritesh Raj SarrafRESEARCHUT -- http://www.researchut.com"Stealing logics from one person is plagiarism, stealing from many is research.""Necessity is the mother of invention."Note: Please CC me. I'm not subscribed to the list-BEGIN PGP SIGNATURE-Version: GnuPG v1.4.2 (GNU/Linux)iD8DBQFDk1Nh4Rhi6gTxMLwRApx0AJ9XHlWFU1J0NdN02gtvimogUSgDkACgmkOO 2pX8ocoC7pot1a8R4u2BWrY==piNo-END PGP SIGNATURE---http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: python 3000 and removal of builtin callable
Mirko Zeibig wrote: This is not an option for e.g. IDEs as some functions might actually do something when called ;-) and I like `callable` for introspection. Other ways would be to check for the `__call__` attribute or use several methods of the `inspect`-Module, both of which are not better than `callable` IMHO. I totally agree with you. The callable function could be moved to a module and be built-in, but it cannot really be removed. Calling a callable and know if an object is a callable without calling it is definitely not the same thing. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
exporting from Tkinter Canvas object in PNG
Hello, I'm new to this mailing list and quite to Pyhon too. I would like to know how to export the contain of the Canvas object (Tkinter) in a PNG file ? Thanks :) Nicolas Pourcelot -- http://mail.python.org/mailman/listinfo/python-list
Reraise exception with modified stack
Hi,
I've made a small utility to re-raise an exception with the same stack
as before with additional information in it. Since I want to keep the
same exception type and that some types have very specific constructors
(which take, for example, more than one parameter), the only safe way I
have found to made it is by hacking the str representation:
import sys
class ExceptionStr:
def __init__(self, content):
self.content = content
self.infos = []
def addinfo(self, info):
self.infos.insert(0, info)
def __call__(self):
return '\n' + '\n'.join(self.infos + [self.content])
def reraise(exception, additionalInfo):
strFunc = getattr(exception, "__str__", None)
if not isinstance(strFunc, ExceptionStr):
strFunc = ExceptionStr(str(exception))
exception.__str__ = strFunc
strFunc.addinfo(additionalInfo)
raise exception, None, sys.exc_info()[-1]
if __name__ == '__main__':
def foo():
raise AttributeError('Test')
def bar():
foo()
try:
try:
try:
bar()
except Exception, exception:
reraise(exception, "While doing x:")
except Exception, exception:
reraise(exception, "While doing y:")
except Exception, exception:
reraise(exception, "While doing z:")
Suppose the resulted traceback is:
Traceback (most recent call last):
File "somefile.py", line 52, in ?
reraise(exception, "While doing z:", MyException)
File "somefile.py", line 50, in ?
reraise(exception, "While doing y:", Exception)
File "somefile.py", line 48, in ?
reraise(exception, "While doing x:")
File "somefile.py", line 46, in ?
bar()
File "somefile.py", line 40, in bar
foo()
File "somefile.py", line 38, in foo
raise AttributeError('Test')
AttributeError:
While doing z:
While doing y:
While doing x:
Test
I would like to know how to code the reraise function so that the lines
48, 50 and 52 don't appear in the stack. Is it possible?
Thx and regards,
Nicolas
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Re: Reraise exception with modified stack
Scott David Daniels wrote: > How about dropping reraise and changing: > reraise(...) > to: > addinfo(...) > raise It doesn't work, or at least it doesn't do what I want. I want to keep the same exception stack to be able to identify the original error. I would like to avoid also writing in the caller something like sys.exc_info()[-1]. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Reraise exception with modified stack
Scott David Daniels wrote: > Have you tried it? Looked to do what you described to me when I run a > sample. Note that is an unadorned raise with no args. The idea is to > simply modify the exception object and then use raise to carry the > whole original exception along as if not intercepted. Oups, sorry, I tried it but wrote "raise exception" instead of "raise". Yes, that's a very good idea indeed. I'll change to that. Thx, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Favorite non-python language trick?
Steven D'Aprano wrote: > One of the things I liked in Pascal was the "with" keyword. You could > write something like this: > > with colour do begin > red := 0; blue := 255; green := 0; > end; > > instead of: > > colour.red := 0; colour.blue := 255; colour.green := 0; > > Okay, so maybe it is more of a feature than a trick, but I miss it and it > would be nice to have in Python. > With PEP343 (I guess in Python 2.5), you will be able to do something like: with renamed(colour) as c: c.red = 0; c.blue = 255; c.green = 0 I think however it is bad. Better solutions to me would be: colour.setRgb(0, 255, 0) or c = myVeryLongNameColour c.red = 0; c.blue = 255; c.green = 0 Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Better console for Windows?
Brett Hoerner wrote: > This is a pretty basic, mostly un-python-related question, although I'm > asking because of Python. > > Is there a different shell I can use (other than cmd.com) to run Python > in, where I can full-screen the window (if I pleased), etc? As it is, > things that would run far off the right have to be word wrapped after > very few characters. I don't know if you absolutely want a shell, but if what you want is a Python interactive prompt, I find PyShell coming with wxPython really nice. It has autocompletion and support copy-paste with/without the preceding >>>. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Generating a list of None
Hi, Is it possible to generate a list of `None' ? opts.__dict__.values() below could be represented by [None, None, None] --- def get_options(opts): """Return True or False if an option is set or not""" vals = opts.__dict__.values() for val in vals: if val is not None: return True return False --- This is how I'd like to see it: --- def get_options(opts): """Return True or False if an option is set or not""" vals = opts.__dict__.values() for if vals is [None * len(vals)]: return False return True --- -- http://mail.python.org/mailman/listinfo/python-list
Re: Generating a list of None
of course the later snipplet should be: --- def get_options(opts): """Return True or False if an option is set or not""" vals = opts.__dict__.values() if vals == [None * len(vals)]: return False return True --- -- http://mail.python.org/mailman/listinfo/python-list
pyQT 4
hello,
i'm using actually pyqt 3.x to create several tools under linux.
I plan to propose those tools also for windows and mac os x under GPL
agreement.
My question is : does anybody know when pyqt 4 will be distributed ?
thanks
Nicolas
--
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getting Arrays and variables from R
hello,
i don't know if this is the best list to send this question, but i'm
already trying to ask.
I need to import variables from .RData files (arrays or variables).
I'm trying to use the rpy module, but without success beccause when i
try to access to a variable loaded from the .RData file i have a
segmentation fault !
This is what i'm doing :
- in R-projet, i create a .RData file with some variables :
> tab<-c(2,5,8,6)
> v<-0.5
> save.image("file.RData")
- in Python :
> from rpy import *
> r.load("file.RData")
['tab', '.Traceback', 'v']
> r.tab
segmentation fault !
I don't understand very well what does python crash.
If someone has an idea to solve my problem or to give me a method which
permit to import arrays and variables from .RData files with another module.
Thanks
Nicolas
--
http://mail.python.org/mailman/listinfo/python-list
Re: getting Arrays and variables from R [fixed]
Nicolas Lebas a écrit :
>hello,
>
>i don't know if this is the best list to send this question, but i'm
>already trying to ask.
>
>I need to import variables from .RData files (arrays or variables).
>I'm trying to use the rpy module, but without success beccause when i
>try to access to a variable loaded from the .RData file i have a
>segmentation fault !
>
>This is what i'm doing :
>- in R-projet, i create a .RData file with some variables :
> > tab<-c(2,5,8,6)
> > v<-0.5
> > save.image("file.RData")
>
>- in Python :
> > from rpy import *
> > r.load("file.RData")
>['tab', '.Traceback', 'v']
> > r.tab
>segmentation fault !
>
>I don't understand very well what does python crash.
>
>If someone has an idea to solve my problem or to give me a method which
>permit to import arrays and variables from .RData files with another module.
>
>Thanks
>
> Nicolas
>
>
Finally, i found the solution with rpy.
There is a bug in the python2.4-rpy_0.4.1 release, so you have to use
instead of 'r.tab' command :
r.get('tab')
--
Nicolas Lebas
INRA Unité Mixte de Recherche INRA / INAPG "Environnement et Grandes
Cultures"
78850 Thiverval - Grignon
France
Tél. +33 (0)1 30 81 55 55 (standard)
Fax +33 (0)1 30 81 55 63
Site Web : www-egc.grignon.inra.fr
--
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Re: getting Arrays and variables from R [fixed]
Finally i found the solution in Rpy-list : there is a bug in
python2.4-rpy_0.4.1.
An alternative solution which works fine it's to use the R get(str)
function instead of using directly the variable (i.e r.tab) like that :
r.get('tab')
Nicolas Lebas a écrit :
> hello,
>
> i don't know if this is the best list to send this question, but i'm
> already trying to ask.
>
> I need to import variables from .RData files (arrays or variables).
> I'm trying to use the rpy module, but without success beccause when i
> try to access to a variable loaded from the .RData file i have a
> segmentation fault !
>
> This is what i'm doing :
> - in R-projet, i create a .RData file with some variables :
> > tab<-c(2,5,8,6)
> > v<-0.5
> > save.image("file.RData")
>
> - in Python :
> > from rpy import *
> > r.load("file.RData")
> ['tab', '.Traceback', 'v']
> > r.tab
> segmentation fault !
>
> I don't understand very well what does python crash.
>
> If someone has an idea to solve my problem or to give me a method which
> permit to import arrays and variables from .RData files with another module.
>
> Thanks
>
> Nicolas
--
http://mail.python.org/mailman/listinfo/python-list
Re: getting Arrays and variables from R
Finally i found the solution in Rpy-list : there is a bug in
python2.4-rpy_0.4.1.
An alternative solution which works fine it's to use the R get(str)
function instead of using directly the variable (i.e r.tab) like that :
r.get('tab')
This bug is fixed in the rpy_0.4.6 release.
Nicolas Lebas a écrit :
> hello,
>
> i don't know if this is the best list to send this question, but i'm
> already trying to ask.
>
> I need to import variables from .RData files (arrays or variables).
> I'm trying to use the rpy module, but without success beccause when i
> try to access to a variable loaded from the .RData file i have a
> segmentation fault !
>
> This is what i'm doing :
> - in R-projet, i create a .RData file with some variables :
> > tab<-c(2,5,8,6)
> > v<-0.5
> > save.image("file.RData")
>
> - in Python :
> > from rpy import *
> > r.load("file.RData")
> ['tab', '.Traceback', 'v']
> > r.tab
> segmentation fault !
>
> I don't understand very well what does python crash.
>
> If someone has an idea to solve my problem or to give me a method which
> permit to import arrays and variables from .RData files with another module.
>
> Thanks
>
> Nicolas
--
http://mail.python.org/mailman/listinfo/python-list
PEP: Specialization Syntax
Hi everyone, I would to know what do you think of this PEP. Any comment
welcomed (even about English mistakes).
PEP:XXX
Title: Specialization Syntax
Version:$Revision: 1.10 $
Last-Modified: $Date: 2003/09/22 04:51:49 $
Author: Nicolas Fleury
Status: Draft
Type: Standards Track
Content-Type: text/plain
Created:24-Jul-2005
Python-Version: 2.5
Post-History:
Abstract
This PEP proposes a syntax in Python to do what is called in
this document "specialization". It contains more than one
proposal:
- Extend square brackets syntax to allow a full call syntax,
using a __specialize__ method, similarly to the __call__
method.
- Extend function definition syntax to allow specialization
of functions.
- Parameterized types.
Motivation
In his controversial blog entry "Adding Optional Typing to
Python -- Part II" [1], Guido Van Rossum introduced the idea
of "parameterized types" in Python. The proposition was to
use [square brackets] rather than to allow
prototyping with __getitem__ method. However, the __getitem__
method is not flexible enough. It doesn't support keyword
arguments and using multiple and default arguments can be pain,
since the only argument received would be a tuple. Calling
can also be error-prone if a tuple can be allowed as a first
argument. This PEP proposes to enhance square brackets syntax
to allow full-call syntax as with parenthesis.
Note that Guido dropped the idea, for now, of parameterized
types in a following blog entry [2]. This PEP introduces
parameterized types only as a last step, and focus more on
having a syntax to prototype them. This PEP can also serve
as a place to discuss to feature of specialization independently.
The term "specialization" is used in that document because
"parameterized functions" would sound like an already available
feature. As Guido pointed out [1], "generic" is neither a good
term. Specialization is a term in that case borrowed from C++.
The term alone is not perfect, since it refers to the action of
passing arguments to a "parameterized type" (or function) to
make it usable and a term must still be found to describe the
"unspecialized" type or function.
Another motivation to this PEP is the frequent usage in Python
of functions to create functions. This pattern is often used
to create callback functions and decorators, to only name these.
However, the fact that both the creation and the use is using
parenthesis can be confusing. Also, a programmer ends up naming
two functions, when only the creating one is called by name and
the created one is doing the job. Some programmers ends up
naming the creating function with the name they would want to
give to the created function, confusing even more the code using
it. To fix this situation, this PEP proposes a syntax for
function specialization.
__specialize__ Special Member Function.
The first element of this proposal is the addition of the
__specialize__ special member function. The __specialize__
function can have the same signatures as __call__. When
defined, the definition of __getitem__ has no effect, and
__specialize__ will be called instead.
The language grammar is extended to allow keyword arguments
and no arguments. For example:
class MyObject(object):
def __specialize__(self, a=4, b=6, *args, **kwargs):
pass
obj = MyObject()
obj[b=7, a=8, c=10]
obj[]
Note that when __specialize__ is defined, __setitem__,
__getslice__ and __setslice__ are still used as before.
The specializer Decorator
To explain the syntaxes proposed in this PEP, the following
decorator is used:
class Specializer:
def __init__(self, callableObj):
self.callableObj
self.__name__ = callableObj.__name__
def __specialize__(self, *args, **kwargs):
self.callableObj(*args, **kwargs)
def specializer(callableObj):
return Specializer(callableObj)
It takes a callable and make it callable with square brackets
instead.
Function Specialization
A common pattern in Python is to use a function to create
another function:
def makeGetMemberFunc(memberName):
def getMember(object):
return getattr(object, memberName)
return getMember
foo(makeGetMemberFunc('xyz'))
The second element of this proposal is to add a syntax so
that the previous example can be replaced by:
def getMember[memberName](object):
Re: PEP: Specialization Syntax
Martin v. Löwis wrote:
> -1. I don't see the point of this PEP. Apparently, you want to define
> parametrized types - but for what purpose? I.e. what are the specific
> use cases for the proposed syntax, and why do you need to change the
> language to support these use cases? I very much doubt that there are
> no acceptable alternatives for each case.
Well, I'm using the alternatives. For example, where I work we have
built a small framework to create binary data to be loaded-in-place by
C++ code (it might be presented at next GDC (Game Developer
Conference)). It uses metaclasses and descriptors to allow things like:
class MyObject(LoadInPlaceObject):
size = Member(Int32)
data = Member(makeArrayType(makePtrType(MyObject2, nullable=True)))
...
I know, it's not really Python, but still, defining functions like
makeArrayType and makePtrType is a pain. It is necessary to maintain a
dictionary of types (to avoid redundacy) and simple things like:
def makeType(someArgument):
class MyObject:
someArgument = someArgument
return MyObject
are not allowed. So its ends up with something like:
__arrayTypes = {}
def makeArrayType(arg1, arg2=someDefault):
if (arg1, arg2) in __arrayTypes:
return __arrayTypes[arg1, arg2]
renamed_arg1 = arg1
renamed_arg2 = arg2
class Array:
arg1 = renamed_arg1
arg2 = renamed_arg2
...
__arrayTypes[arg1, arg2] = Array
return Array
Does it qualify as an "acceptable alternative"? when it could have been:
class Array[arg1, arg2=someDefault]:
...
I probably should have put this example in the PEP.
> IOW, whatever it is that you could do with this PEP, it seems you could
> do this today easily.
The PEP validity is also very much influenced if optional static typing
is planned to be added to the language. I realize defending this PEP is
much harder without static typing and my use cases imply typing of some
sort anyway.
Regards,
Nicolas
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Re: PEP: Specialization Syntax
Bengt Richter wrote:
>>__specialize__ Special Member Function.
>
> By "Member Function" do you mean anything different from "method"?
No, I should have written method. C++ habit.
>>The first element of this proposal is the addition of the
>>__specialize__ special member function. The __specialize__
>>function can have the same signatures as __call__. When
>
> Any function can have any legal signature, so I'm not sure what you are
> saying.
You're right, I should focus on the syntax change, to call __getitem__
(or __specialize__) automatically.
>>defined, the definition of __getitem__ has no effect, and
>>__specialize__ will be called instead.
>
> What about subclassing and overriding __getitem__ ?
I have no problem with that. I even suggest it at the end of the PEP.
But don't you think the name "__getitem__" is not appropriate then?
> here you can currently write
> __getitem__ = __specialize__
> although you have to remember that obj[:] and related slicing expressions
> become legal and that obj[] does not, without a language sysntax change.
Yes, the PEP is about that syntax change.
>>class Specializer:
>>def __init__(self, callableObj):
>>self.callableObj
>
>^^?? = callableObj ?
Yes, "= callableObj" is missing.
>>A common pattern in Python is to use a function to create
>>another function:
>>
>>def makeGetMemberFunc(memberName):
>>def getMember(object):
>>return getattr(object, memberName)
>>return getMember
>>
>>foo(makeGetMemberFunc('xyz'))
>
>
> Either closures like the above or bound methods work for this,
> so you just want more concise spelling?
In the case of functions, yes. For functions, I guess the syntax is
much more useful is static typing is added, or planned to be added, in
the language. However, there's still use cases where it is useful.
> Have you looked at currying? E.g.,
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52549
And partial will be in Python 2.5 (PEP 309). Yes, I've look at it, but
in my use cases the created function correspond to a specific function
signature, so, for example, you always only want to specify the
"memberName" argument. Currying is nice, but since any argument can
supplied, the code is less self-documenting. But I used these in
day-to-day programming.
>>class MyList[ElementType=object](List[ElementType]):
>>...
>
> Before I'd want to extend class syntax this way, I think I'd want to
> explore some other aspects of class syntax as well, with more (and
> more persuasive) use cases in view. Also more thought to what is done
> when and whether the issue is to supply information into existing control
> contexts or to modify control flow as well, to extend possibilities for
> customized processing.
What do you think of the example I post in a reply to Martin v.Lowis?
>>Instead of adding a __specialize__ method, the __getitem__
>
> When you say "the" __getitem__ method, what do you mean? AFAIK the
> method itself is an unrestricted function. It just happens that
> binding it as a class attribute __getitem__ makes it get called
> from code with square bracket access spellings. I think that's where
> your changes to allow "additional signatures" would have to go. I.e.,
> in generation of code from the "calling" syntax. To illustrate:
>
> >>> class C(object):
> ... def __getitem__(self, *args, **kwargs):
> ... return self, args, kwargs
> ...
> >>> c=C()
> >>> c[1]
> (<__main__.C object at 0x02EF498C>, (1,), {})
> >>> c[1,2]
> (<__main__.C object at 0x02EF498C>, ((1, 2),), {})
> >>> c[:]
> (<__main__.C object at 0x02EF498C>, (slice(None, None, None),), {})
> >>> c[kw='key word arg']
>File "", line 1
> c[kw='key word arg']
> ^
> SyntaxError: invalid syntax
>
> But here the problem is not in the __getitem__ method:
>
> >>> c.__getitem__(kw='key word arg')
> (<__main__.C object at 0x02EF498C>, (), {'kw': 'key word arg'})
>
> It's just that square bracket expression trailer syntax does not
> allow the same arg list syntax as parenthesis calling trailer syntax.
I totally agree and that's what I mean. The formulation of the PEP is
wrong, I should almost not talk about __getitem__ since as you said it
can have any signature. The PEP is about extending [] syntax to call
automtically __getitem__ function with more complex signatures.
>>Should other operators that square brackets be used for
>>specialization?
>
> Didn't quite parse that ;-) You mean list comprehensions? Or ??
I mean should angle brackets <> like in C++, or another operator, be
used instead?
Regards and thx for your feedback,
Nicolas
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Re: PEP: Specialization Syntax
Bengt Richter wrote:
> I don't understand why you wouldn't give the function arg a different name
> in the first place instead of via a temporary intermediary binding, e.g.,
>
> def makeType(someArgument_alias):
> class MyObject:
> someArgument = someArgument_alias
> return MyObject
Because that would affect documentation and keyword arguments. Both the
constructed class *and* the function are exposed to the user, so it
needs to be coherent.
>>__arrayTypes = {}
>>def makeArrayType(arg1, arg2=someDefault):
>>if (arg1, arg2) in __arrayTypes:
>>return __arrayTypes[arg1, arg2]
>>renamed_arg1 = arg1
>>renamed_arg2 = arg2
>>class Array:
>> arg1 = renamed_arg1
>> arg2 = renamed_arg2
>>...
>>__arrayTypes[arg1, arg2] = Array
>>return Array
>>
>
> Or (untested, using new style class):
>
> def makeArrayType(arg1, arg2=someDefault):
> try: return __arrayTypes[arg1, arg2]
> except KeyError:
> __arrayTypes[arg1, arg2] = Array = type('Array',(),{'arg1':arg1,
> 'arg2':arg2})
> return Array
>
> (just re-spelling functionality, not understanding what your real use case is
> ;-)
Well, of course, but I didn't wrote the rest of the class definition;)
So I need a place to put the class definition. In the end, it looks
very much like the mess in the example. Maybe I'm missing a solution
using decorators. I've defined a few classes like that, and I can live
with it, but having a syntax to do it more easily, I would use it right
away.
I guess it can also be useful for people interfacing with COM or typed
contexts.
Regards,
Nicolas
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Re: PEP: Specialization Syntax
Kay Schluehr wrote:
> def makeClass(cls_name, **kw):
> return type(cls_name,(), kw)
>
>>>>MyObject = makeClass("MyObject",a=8)
>>>>MyObject
As said to Bengt, a place is needed to write the class definition.
There's no need for metaclass in that case:
def makeType(a, b, c=someDefault):
arguments = locals()
class MyObject:
pass # Complete definition here
MyObject.__dict__.update(arguments)
return MyObject
Regards,
Nicolas
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Re: PEP: Specialization Syntax
Kay Schluehr wrote: > I have to admit that i don't actually understand what you want? The > problems you try to solve seem trivial to me but it's probably my fault > and i'm misreading something. You might be correct that your PEP may be > interesting only if "optional static typing" will be introduced to Py3K > and then we will suddenly have an immediate need for dealing with > generic types so that the syntax can be reused for deferred functions ( > the concept of "specialization" is usually coupled with some kind of > partial evaluation which doesn't take place somewhere in your proposal > ). But i'm not sure if this makes sense at all. Well, the partial evaluation is done when using []. def getMember[memberName](obj): return getattr(obj, memberName) x = getMember["xyz"] # specialization y = x(obj) # use I realize the term "specialization" can be confusing, since people might think of what is called in C++ "explicit specialization" and "partial specialization", while these concepts are not present in the PEP. The point is that I'm already using static-like typing in frameworks interacting with other languages with generic types. So I would already benefit from such a capability, and yes, there's workarounds. I'm clearly in a minority with such a need, but the first point fo the PEP is to extend [] syntax, so that it is possible to prototype generic types using [] operators. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP: Specialization Syntax
Bengt Richter wrote: > On Sun, 07 Aug 2005 21:41:33 -0400, Nicolas Fleury <[EMAIL PROTECTED]> wrote: >>I mean should angle brackets <> like in C++, or another operator, be >>used instead? > > I am getting the feeling that your PEP is about a means to do something > C++-like > in python, not necessarily to enhance python ;-) IOW, it seems like you > want the [] to do something like C++ in templates? Yes, exactly. Actually Guido also mentionned pointy brackets: http://www.artima.com/weblogs/viewpost.jsp?thread=86641 > (BTW, I have nothing against giving python new capabilities (quite the > reverse), > but not by grafting limbs from other animals ;-) If I look at a very recent blog entry of Guido, it seems the idea is still in the air: http://www.artima.com/weblogs/viewpost.jsp?thread=92662 > Maybe you want hidden name-mangling of function defs according to arg types > and corresponding dispatching of calls? I am afraid I am still not clear > on the fundamental motivation for all this ;-) I wrote the PEP to see if was the only one that would benefit from generic types *before* having optional static typing in the language. It seems I'm the only one;) According to blog entry 86641, Guido himself is prototyping with __getitem__. However, I cannot do the same, because the framework I use is much more complete and keyword arguments are a must. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP: Specialization Syntax
Bengt Richter wrote: > On Mon, 08 Aug 2005 16:18:50 -0400, Nicolas Fleury <[EMAIL PROTECTED]> wrote: >>I wrote the PEP to see if was the only one that would benefit from >>generic types *before* having optional static typing in the language. >> >>It seems I'm the only one;) >> >>According to blog entry 86641, Guido himself is prototyping with >>__getitem__. However, I cannot do the same, because the framework I use >>is much more complete and keyword arguments are a must. >> > Here is a decorator object to set up function call dispatch according to type. > It only uses positional arguments, but could be fleshed out, I think. > Not tested beyond what you see ;-) That's nice. Guido also posted this multimethods solution: http://www.artima.com/weblogs/viewpost.jsp?thread=101605 The only thing I was saying it that I can use generic types in Python right now (and I do), by using (), but I can't with what will probably be the syntax in future, i.e. using []. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP: Specialization Syntax
Martin v. Löwis wrote:
> Nicolas Fleury wrote:
>
>>Well, I'm using the alternatives.
>
> Perhaps not to the full power.
Not perhaps, surely;) Who does anyway;)
> So you don't want to write the makeArrayType function, right?
>
> How about this:
>
> # declaration
> class Array(object):
> __typeargs__ = ['arg1', ('arg2', someDefault)]
> ...
>
> # use
> t = specialize(Array, arg1=Int32)
>
> where specialize is defined as
>
> def specialize(ptype, *args):
> result = type(ptype.__name__, (ptype,), args)
> for t in result.__typeargs__:
> if isinstance(t, string):
> if not hasattr(result, t):
> raise TypeError("missing parameter "+t)
> else:
> name,val = t
> if not hasattr(result, name):
> setattr(result, val)
>return result
That exact solution would not work for me, since that would replace the
class metaclass, right? However, you have a good point. Such a
function could be done by using the class metaclass instead of type,
passing the base classes and dictionary (basically copying the class)
and using a dictionary with args values as a key to avoid redundacies
(can't see if there's something else).
Thx and regards,
Nicolas
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Re: win32pipe.popen3
Jakob Simon-Gaarde wrote: > Follow-up on a thread from 1999 (see below) > > Well now it is 2005 and the operating system I'm using is Windows > Server 2003, and I can still see that the same problem persists with: > > win32pipe.popen2() > win32pipe.popen3() > win32pipe.popen4() > > while win32pipe.popen() does almost what you want. Have you tried subprocess? Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Basic Server/Client socket pair not working
Michael Goettsche wrote:
> Hi there,
>
> I'm trying to write a simple server/client example. The client should be able
> to send text to the server and the server should distribute the text to all
> connected clients. However, it seems that only the first entered text is sent
> and received. When I then get prompted for input again and press return,
> nothing gets back to me. Any hints on what I have done would be very much
> appreciated!
>
> Here's my code:
>
> SERVER ##
> import socket
> import select
>
> mySocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> mySocket.bind(('', 1))
> mySocket.listen(1)
>
> clientlist = []
>
> while True:
>connection, details = mySocket.accept()
>print 'We have opened a connection with', details
>clientlist.append(connection)
>readable = select.select(clientlist, [], [])
>msg = ''
>for i in readable[0]:
for i in readable:
> while len(msg) < 1024:
> chunk = i.recv(1024 - len(msg))
> msg = msg + chunk
>
>for i in clientlist:
> totalsent = 0
> while totalsent < 1024:
> sent = i.send(msg)
> totalsent = totalsent + sent
>
> ## CLIENT
> import socket
> import select
>
> socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> socket.connect(("127.0.0.1", 1))
>
> while True:
> text = raw_input("Du bist an der Reihe")
> text = text + ((1024 - len(text)) * ".")
> totalsent = 0
> while totalsent < len(text):
> sent = socket.send(text)
> totalsent = totalsent + sent
>
> msg = ''
> while len(msg) < 1024:
> chunk = socket.recv(1024 - len(msg))
> msg = msg + chunk
>
> print msg
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Import mechanism to support multiple Python versions
Hi, I'm trying to support two Python versions at the same time and I'm trying to find effective mechanisms to support modules compiled in C++ transparently. All my code in under a single package. Is it possible to override the import mechanism only for modules under that package and sub-packages so that?: import cppmymodule would be equivalent to: if sys.version == "2.4": import cppmymodule24 as cppmymodule elif sys.version == "2.3": import cppmymodule23 as cppmymodule for all modules under the package and all modules with names beginning with cpp (or another way to identify them). I have also third party packages. Is it possible to make a package point to another folder? For example: psyco23/... psyco24/... psyco/__init__.py => points to psyco23 or psyco24 depending on Python version used. Note that I cannot use .pth files or symbolic links, since I would want the exact same code hierarchy to work with both Python 2.3 and 2.4. Any help appreciated. Thx and regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Import mechanism to support multiple Python versions
Nicolas Fleury wrote:
import cppmymodule
would be equivalent to:
if sys.version == "2.4":
import cppmymodule24 as cppmymodule
elif sys.version == "2.3":
import cppmymodule23 as cppmymodule
for all modules under the package and all modules with names beginning
with cpp (or another way to identify them).
Since all my imports are absolute, my code looks more like:
import root.subpackage.cppmymodule
So I guess, I can add this in root/__init__.py and everything would be fine:
def myimport(name, globals=None, locals=None, fromlist=None,
__import__=__import__):
names = name.split('.')
if names[0] == 'root' and names[-1][0:3] == 'cpp':
name += '%s%s' % sys.version_info[0:2]
return __import__(name, globals, locals, fromlist)
__builtins__['__import__'] = myimport
It seems to work, is that right?
Thx and regards,
Nicolas
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Re: getattr() woes
David M. Cooke wrote: Ideally, I think the better way is if getattr, when raising AttributeError, somehow reused the old traceback (which would point out the original problem). I don't know how to do that, though. Maybe a solution could be to put the attribute name in the AttributeError exception object, and use it in getattr; if the name doesn't match, the exception is re-raised. It's still not flawless, but would reduce risk of errors. Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Why would I use inspect.isclass()?
an_instance=Abc() But what good is that? Of course I know Abc is a class, why would I want to inspect it so that it would tell me what I already know? Well, for no reason in that case. For the same reason you would not call isinstance(an_instance, Abc) if you already know an_instance is an instance of Abc. def Hello(self, some_class): # since I don't know if the argument passed down *is* a class or not, I would: if inspect.isclass(some_class)==True: ... return ### But that obviously isn't what isclass is for. What should I use? Well, it's obviously what isclass is for;) (By the way, you would be better not compare your conditions with True, unless it's really what you want). I guess another example would be an assert on the type of argument: def foo(someClass): assert inspect.isclass(someClass) # rest of code This way errors on types are handled at the beginning and at the same time the code it documenting itself. The function could also be useful in cases where you do some C++-like overloading mechanism. Anyway, isclass, like iscallable, are functions that are not used often, but you still might need them. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Why would I use inspect.isclass()?
It's me wrote: I guess another example would be an assert on the type of argument: def foo(someClass): assert inspect.isclass(someClass) # rest of code But that would always fail! (I just tried it). Are you sure you haven't pass an instance instead of a class? Remember, classes are also objects in Python: >>> import inspect >>> class A: pass ... >>> def foo(a): assert inspect.isclass(a) ... >>> foo(A) >>> Works fine and makes sense, no? Of course, if I pass an instance instead of a class it would fail: >>> myA = A() >>> foo(myA) Traceback (most recent call last): File "", line 1, in ? File "", line 1, in foo AssertionError Maybe your question is in what situations passing a class can be useful? There's many examples and once you're used to that capability it can be powerful. One simple example could be the generation of documentation; since you usually want to doc your classes, not instances. So it would make sense to do something like: def writeHtmlDoc(file, someClass): ... Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Why would I use inspect.isclass()?
it's me wrote: Okay, Nick, I didn't know you can pass a "Class" rather then an instance. I have to chew on what your example does. But no, I want to pass an instance of a Class. But how do I know that the calling routine *did* pass me a class - pardon me: an instance of a Class? You have the builtin function isinstance: class A: pass a = A() print isinstance(a, A) # True Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
How to use subprocess
Hi, I want to use the subprocess module (or any standard Python module) to run a process: - which stdout and stderr can each be redirected to any file-like object (no fileno function). - can be cancelled with a threading.Event. My problem is that the subprocess.Popen constructor doesn't seem to support file-like objects (only file objects with fileno()). If I use subprocess.PIPE, I have the problem that the read functions of of the subprocess objects stdout and stderr are blocking (and I want to redirect them to different file-like objects, so I definitely need non-blocking access). How am I supposed to do it? Thx and regards, Nicolas It something like that that I would need to make work (but supporting file-like objects): class CancellationException(Exception): pass class CancellableCommand: def __init__(self, command, stdout=nullFile, stderr=nullFile, refreshDelay=0.1, raiseIfNonZero=True): self.command = command self.stdout = stdout self.stderr = stderr self.refreshDelay = refreshDelay def execute(self, cancelEvent=None): if cancelEvent is None: cancelEvent = threading.Event() # dummy exitCode = None cmd = subprocess.Popen( self.command, stdout=self.stdout, stderr=self.stderr) while exitCode is None: # Wait for event to be set for a specific delay cancelEvent.wait(self.refreshDelay) if cancelEvent.isSet(): kill(cmd.pid) # implemented as in FAQ raise CancellationException( 'Process "' + self.command + '" cancelled') exitCode = cmd.poll() return exitCode -- http://mail.python.org/mailman/listinfo/python-list
Once again a unicode question
Hello,
I'm puzzled by this test I made while trying to transform a page in
html to plain text. Because I cannot send unicode to feed, nor str so
how can I do this ?
[EMAIL PROTECTED]:~$ python2.4
.Python 2.4.1c2 (#2, Mar 19 2005, 01:04:19)
.[GCC 3.3.5 (Debian 1:3.3.5-12)] on linux2
.Type "help", "copyright", "credits" or "license" for more information.
.>>> import formatter
.>>> import htmllib
.>>> html2txt = htmllib.HTMLParser(formatter.AbstractFormatter(formatter.DumbWriter()))
.>>> html2txt.feed(u'D\xe9but')
.Traceback (most recent call last):
. File "", line 1, in ?
. File "/usr/lib/python2.4/sgmllib.py", line 95, in feed
.self.goahead(0)
. File "/usr/lib/python2.4/sgmllib.py", line 120, in goahead
.self.handle_data(rawdata[i:j])
. File "/usr/lib/python2.4/htmllib.py", line 65, in handle_data
.self.formatter.add_flowing_data(data)
. File "/usr/lib/python2.4/formatter.py", line 197, in add_flowing_data
.self.writer.send_flowing_data(data)
. File "/usr/lib/python2.4/formatter.py", line 421, in send_flowing_data
.write(word)
.UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 1: ordinal not in range(128)
.>>> html2txt.feed(u'D\xe9but'.encode('latin1'))
.Traceback (most recent call last):
. File "", line 1, in ?
. File "/usr/lib/python2.4/sgmllib.py", line 94, in feed
.self.rawdata = self.rawdata + data
.UnicodeDecodeError: 'ascii' codec can't decode byte 0xe9 in position 1: ordinal not in range(128)
.>>> html2txt.feed('Début')
.Traceback (most recent call last):
. File "", line 1, in ?
. File "/usr/lib/python2.4/sgmllib.py", line 94, in feed
.self.rawdata = self.rawdata + data
.UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 1: ordinal not in range(128)
.>>>
--
(°> Nicolas Évrard
/ ) Liège - Belgique
^^
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Re: Once again a unicode question
* Serge Orlov [23:45 26/03/05 CET]: Nicolas Evrard wrote: Hello, I'm puzzled by this test I made while trying to transform a page in html to plain text. Because I cannot send unicode to feed, nor str so how can I do this ? Seems like the parser is in the broken state after the first exception. Feed only binary strings to it. That was that thank you very much. -- (°> Nicolas Évrard / ) Liège - Belgique ^^ -- http://mail.python.org/mailman/listinfo/python-list
Re: list-comprehension and map question (simple)
* Charles Hartman [16:51 27/03/05 CEST]: I understand this toy example: lines = "this is a group\nof lines of\nwords" def getlength(w): return len(w) s = map(getlength, [word for ln in lines.split() for word in ln.splitlines()]) (now s is [4, 2, 1, 5, 2, 5, 2, 5]) My question is whether there's any compact way to combine function calls, like this (which doesn't work): lines = "this is a group\nof lines of\nwords" def getlength(w): return len(w) def timestwo(x): return x * 2 s = map(timestwo(getlength), [word for ln in lines.split() for word in ln.splitlines()]) I hope the question is clear enough. I have a feeling I'm ignoring a simple technique . . . lambda ! map(lambda x: timestwo(getlength(x)), ...) -- (°> Nicolas Évrard / ) Liège - Belgique ^^ -- http://mail.python.org/mailman/listinfo/python-list
threading.Event file descriptor
Hi, Is there any way to get the file descriptor on Unix or handle on Windows associated internally with a threading.Event object? So that it can be used in a call to select or WaitForMultipleObjects. Thx and regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: threading.Event file descriptor
[EMAIL PROTECTED] wrote: There is no event handle used in Event object (for NT at least). Do not know about Linux... And there's no handle at all? It's not important if it's not an event handle as long as it is an handle usable with WaitForMultipleObjects. Also, I don't understand how it will be possible to implement threading.Event without using finally, at the lower level, a handle, since as far as I know this is the mechanisms the OS offers. Unless you want to rewrite the interpreter (namelly PyThread_allocate_lock.c) for platforms you are talking about, you would be better of, if you create your own class (derived from Event, and ovewritte aquire, release and wait methods). I wouldn't want to derive from Event since my goal would be to submit a patch to make subprocess.Popen.wait take an optional threading.Event to kill the process. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: threading.Event file descriptor
[EMAIL PROTECTED] wrote: //And there's no handle at all? There is one (check thread_nt.h) you have to "propagate" HANDLE to Pythom level. That's why, you have to change the interpreter. Do not forget, that thread is a build-in module. Sounds fine with me. A fileno (or whatever) function can be added to threading.Event on all platforms, giving access to internal file descriptor/handle. //I wouldn't want to derive from Event since my goal would be to submit a patch to make subprocess.Popen.wait take an optional threading.Event to kill the process. And that's it? Right now aquire_lock is non-interruptable, as a result your Popen.wait is also non-interruptable, but if you pass derived event you will be able to handle more generic cases. I'm not 100% sure I understand what you say. Support killing the process with any handle, not only an event, would be a good thing. But it doesn't change the fact that, IMHO, the usefulness of threading.Event is just too limited if it doesn't support select or WaitForMultipleObjects. I think also that threading.Thread should give access to its internal handle (at least thread module does). Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: pre-PEP: Suite-Based Keywords
Shane Hathaway wrote: I like this PEP a lot, but your concern is valid. Maybe Brian could modify the PEP slightly to disambiguate. How about using an ellipsis in the argument list to signify suite-based keywords? Examples: f(...): x = 1 class C(object): x = property(...): doc = "I'm the 'x' property." def fget(self): return self.__x def fset(self, value): self.__x = value def fdel(self): del self.__x d = dict(...): a = 1 b = 2 Using an ellipsis in a statement that would begin a different kind of block is illegal and generates a syntax error. Note that this usage seems to fit well with the definition of "ellipsis". http://dictionary.reference.com/search?q=ellipsis Shane I like the ellipsis syntax a lot, it greatly helps the proposal IMHO. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Pythonic way to do static local variables?
Charles Krug wrote: I've a function that needs to maintain an ordered sequence between calls. In C or C++, I'd declare the pointer (or collection object) static at the function scope. What's the Pythonic way to do this? Is there a better solution than putting the sequence at module scope? Thanks. You might want a generator. Search for yield keyword. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: E-commerce system in Python
* Arshpreet Singh [2016-03-18 05:25 +0100]: I am looking for an E-commerce system in python to sell things things online, which can also be responsive for Android and IOS. A quick Google search brought me http://getsaleor.com/ it uses Django, Is there any available one using Flask or newly born asyncio based framework? You could build your own e-commerce system using Tryton and flask-tryton. http://www.tryton.org/ https://pypi.python.org/pypi/flask_tryton We're in the process of adding basic cart functionalities to the ERP. It will probably be included in the near future. -- Nicolas Évrard - B2CK SPRL E-mail/Jabber: [email protected] Tel: +32 472 54 46 59 Website: http://www.b2ck.com/ -- https://mail.python.org/mailman/listinfo/python-list
Which type should be used when testing static structure appartenance
Hello,
I saw the following retweet by Raymond Hettinger in this morning:
https://twitter.com/sanityinc/status/666485814214287360
Programming tip: many of those arrays and hashes in your code
should actually be sets. Match data structures to data
constraints!
I saw just in time because in a review I wrote something like this:
if operator not in ('where', 'not where')
and my colleague proposed that I should use a list instead of a tuple.
But reading the mentioned tweet I tend to think that a set would be a
better choice.
What are your opinion on this issue (I realize it's not something of
the utmost importance but rather a "philosophical" question).
--
Nicolas Évrard - B2CK SPRL
E-mail/Jabber: [email protected]
Tel: +32 472 54 46 59
Website: http://www.b2ck.com/
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Re: MySQLdb Python API: Unable to connect
Dennis Lee Bieber wrote: >On 26 Dec 2005 21:39:11 -0800, "Mondal" <[EMAIL PROTECTED]> declaimed >the following in comp.lang.python: > > > >c=MySQLdb.Connect(host='localhost',user='root',passwd='',db='shop',port=3306) > > > > So what is that - doing in the port number... So far as I know, >nothing reasonable lives on port 324... > > > I don't see anything with 324 in there ? What do you mean ? > If that is supposed to be the standard MySQL port, just leave it >off... Granted, I'm not running 5.x... (and I'm behind both a router >firewall and a software firewall AND MySQL's own authorization scheme, >so the user/password won't do anyone any good at getting into my system) > >myDB = MySQLdb.connect(host="localhost", > user="BestiariaCP", > #passwd="web-asst", > db="bestiaria") > > Note the lack of a port number specification. The default port for >MySQL is 3306; if your server is running on the default, you don't need >to specify it. Error 10061 is the generic Windows socket "connection >refused" -- since I doubt you have anything on port 324, that is to be >expected. > > Just to make sure, ( Not trying to be a smart ass) are you sure the database is running ? That seems like the most obvious thing. Nic -- http://mail.python.org/mailman/listinfo/python-list
Patch : doct.merge
Hi, I've posted this patch on Source forge : http://sourceforge.net/tracker/index.php?func=detail&aid=1391204&group_id=5470&atid=305470 If you want to update a dictionary with another one, you can simply use update : a = dict(a=1,c=3) b = dict(a=0,b=2) a.update(b) assert a == dict(a=0,b=2,c=3) However, sometimes you want to merge the second dict into the first, all while keeping the values that are already defined in the first. This is useful if you want to insert default values in the dictionary without overriding what is already defined. Currently this can be done in a few different ways, but all are awkward and/or inefficient : a = dict(a=1,c=3) b = dict(a=0,b=2) Method 1: for k in b: if k not in a: a[k] = b[k] Method 2: temp = dict(b) temp.update(a) a = temp This patch adds a merge() method to the dict object, with the same signature and usage as the update() method. Under the hood, it simply uses PyDict_Merge() with the override parameter set to 0 instead of 1. There's nothing new, therefore : the C API already provides this functionality (though it is not used in the dictobject.c scope), so why not expose it ? The result is : a = dict(a=1,c=3) b = dict(a=0,b=2) a.merge(b) assert a == dict(a=1,b=2,c=3) Does this seem a good idea to you guys ? Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Patch : doct.merge
Here's method 3 :
# Python 2.3 (no generator expression)
a.update([(k,v) for k,v in b.iteritems() if k not in a])
# Python 2.4 (with generator expression)
a.update((k,v) for k,v in b.iteritems() if k not in a)
It's a bit cleaner but still less efficient than using what's already
in the PyDict_Merge C API. It's even less efficient than method 1 and 2
! Here is the benchmark I used :
import timeit
init = '''a = dict((i,i) for i in xrange(1000) if i%2==0); b =
dict((i,i+1) for i in xrange(1000))'''
t = timeit.Timer('''for k in b:\n\tif k not in a:\n\t\ta[k] =
b[k]''',init)
print 'Method 1 : %.3f'%t.timeit(1)
t = timeit.Timer('''temp = dict(b); temp.update(a); a = temp''',init)
print 'Method 2 : %.3f'%t.timeit(1)
t = timeit.Timer('''a.update((k,v) for k,v in b.iteritems() if k not in
a)''',init)
print 'Method 3 : %.3f'%t.timeit(1)
t = timeit.Timer('''a.merge(b)''',init)
print 'Using dict.merge() : %.3f'%t.timeit(1)
Here are the results :
Method 1 : 5.315
Method 2 : 3.855
Method 3 : 7.815
Using dict.merge() : 1.425
So using generator expressions is a bad idea, and using the new
dict.merge() method gives an appreciable performance boost (~ x 3.73
here).
Regards,
Nicolas
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csv file or sqlite ?
hi, I am programming a filter for websites. to check if an url is in the blacklist, i have used a csv file. i have try to use sqlite but it looks as fast as csv files. Can you tell me if sqlite is faster than csv files ? or not ? thanks ___ Découvrez un nouveau moyen de poser toutes vos questions quelque soit le sujet ! Yahoo! Questions/Réponses pour partager vos connaissances, vos opinions et vos expériences. http://fr.answers.yahoo.com -- http://mail.python.org/mailman/listinfo/python-list
unicode "table of character" implementation in python
Hi, I am handling a mixed languages text file encoded in UTF-8. Theres is mainly French, English and Asian languages. I need to detect every asian characters in order to enclose it by a special tag for latex. Does anybody know if there is a unicode "table of character" implementation in python? I mean, I give a character and python replys me with the language in which the character occurs. Thanks in advance -- http://www.nicolas.pontoizeau.org/ Nicolas Pontoizeau - Promotion EFREI 2005 -- http://mail.python.org/mailman/listinfo/python-list
Re: unicode "table of character" implementation in python
2006/8/22, Brian Beck <[EMAIL PROTECTED]>: > Nicolas, check out the unicodedata module: > http://docs.python.org/lib/module-unicodedata.html > > Find "import unicodedata" on this page for how to use it: > http://www.amk.ca/python/howto/unicode > > I'm not sure if it has built-in support for finding which language block a > character is in, but a table like this might help you: > http://www.unicode.org/Public/UNIDATA/Blocks.txt As usual, Python has a solution that goes beyond my needs! Thanks for the links I will dive into it. Nicolas -- http://www.nicolas.pontoizeau.org/ Nicolas Pontoizeau - Promotion EFREI 2005 -- http://mail.python.org/mailman/listinfo/python-list
Re: Python to tell what is the IP of my PC .
On 11/9/06, Tim Williams <[EMAIL PROTECTED]> wrote: On 8 Nov 2006 15:35:31 -0800, NicolasG <[EMAIL PROTECTED]> wrote:> How can I use python to get the real IP address of my DSL router (when> my PC is part of the local home LAN) ? The router will the PC's default gateway IP address, if you are on awindows platform, you can view it by typing IPCONFIG (enter) from acommand prompt.This is the router local IP, I need to get the router "outside" IP witch is the real one. A quick google, gave me this, look at the comments at the end for anexample of finding the Default Gateway IP address using Python http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/162994import win32api raise the error "module not exsit"and socket.gethostbyname(name)the router doesn't have a hostname.cheers ;)-- Nicolas GSkype: nicolasg_ mobile: +30 69 45 714 578 -- http://mail.python.org/mailman/listinfo/python-list
HTTPBasicAuthHandler doesn't work
Hi !
I'm trying to add the HTTP basic authentification to my web spider but
it doesn't work...
The HTTPBasicAuthHandler don't send the headers for authentification
:-(
Here is the code : http://devloop.lyua.org/releases/lswww_urllib2.py
def
__init__(self,rooturl,firsturl=[],forbidden=[],proxy={},cookie="",auth_basic=[]):
root=rooturl
self.excluded=forbidden
self.proxy=proxy
self.cookie=cookie
self.auth_basic=auth_basic
if root[-1]!="/":
root+="/"
if(self.checklink(root)):
print "Invalid link argument"
sys.exit(0)
for lien in firsturl:
if(self.checklink(lien)):
print "Invalid link argument"
sys.exit(0)
server=(root.split("://")[1]).split("/")[0]
self.root=root
self.server=server
director = urllib2.OpenerDirector()
director.add_handler(urllib2.HTTPHandler())
director.add_handler(urllib2.HTTPSHandler())
if self.proxy!={}:
director.add_handler(urllib2.ProxyHandler(self.proxy))
if self.auth_basic!=[]:
auth=urllib2.HTTPBasicAuthHandler(urllib2.HTTPPasswordMgrWithDefaultRealm())
auth.add_password(None, self.root, self.auth_basic[0],
self.auth_basic[1])
director.add_handler(auth)
if self.cookie!="":
cj = cookielib.LWPCookieJar()
if os.path.isfile(self.cookie):
cj.load(self.cookie,ignore_discard=True)
director.add_handler(urllib2.HTTPCookieProcessor(cj))
urllib2.install_opener(director)
Where is the problem ?
Thanks !
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Re: Python web service ...
If I want to run my program as a web service I need to setup a webserver , am I right ? Whars that difference ? can a webservice be run without a webserver ? On 8/29/06, Jorge Vargas <[EMAIL PROTECTED]> wrote: > On 26 Aug 2006 04:07:35 -0700, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > Hi folks, I have accomplished to make a python program that make some > > image manipulation to bmp files. > > I now want to provide this program as a web service. A user can visit a > > site and through a web interface he should upload the file to the web > > server , the server then will do the image process with the python > > program I have wrote and when it finish the user must get the image > > file back . > > > > My question is how difficult is to set up a web server that can run > > python easy ? should I try ZOPE or there is something better in mind ? > > is that webservice or webserver? > if webservice try ZSI of it's a webserver why don't you try CherryPy? > > > > -- > > http://mail.python.org/mailman/listinfo/python-list > > > -- Nicolas G mobile: +30 69 45 714 578 -- http://mail.python.org/mailman/listinfo/python-list
python and snmp
Hi all, I was just wondering if someone here had any experience with some of these implementations of the snmp protocol? pysnmp, libsnmp, snmpy. Does anybody know of another implementation? thanks in advance!!! -- miya -- http://mail.python.org/mailman/listinfo/python-list
Re: VB to Python migration
Josh wrote: > We have a program written in VB6 (over 100,000 lines of code and > 230 UI screens) that we want to get out of VB and into a better > language. The program is over 10 years old and has already been > ported from VB3 to VB6, a job which took over two years. We would > like to port it to Python, but we need to continue to offer > upgrades and fixes to the current VB6 version. Does anybody know of > ways we could go about rewriting this, one screen at a time, in > Python, and calling the screens from the existing program? > > We are also looking for a graphics toolkit to use. IronPython with > it's .NET bindings and ability to integrate with Visual Studio > looks good, but leaves that bad MS taste in the mouth. > > We currently use a MS Access back end and need to migrate to a > proper SQL server. We need to leave options open for SQL Server > (for customers who want to use existing infrastructure) and > something like MySQL or PostgreSQL. But in the mean time, we need > to be able to access an MSAccess (Jet) database from Python. > > Any answers/suggestions/pointers are greatly appreciated. > > Thanks, > > Josh Isted For the Database, you should use the SQLObject(sqlobject.org) module. Nic -- http://mail.python.org/mailman/listinfo/python-list
Re: Python vs C for a mail server
If your friend is proficient in C/C++ then learning Python should not be a pain. Quite the contrary, it should be an enlightnement. Being good in C/C++ AND Python is a killer combination, as you can promptly and efficiently code big chunks of your application in Python and interface with C/C++ code where (and if) high performance is required. Now, you should definitely check the requirements for the homework. If the assignment is about being able to decipher an RFC and implement it correctly with a nice software design, then I would definitely opt for Python. Having to squish memory management, string manipulation and character encoding bugs in C/C++ is not fun and not related to high-level design nor RFC support. If it's just a way to throw a programming challenge at your friend's face, then you should check whether it's okay to use Python rather than C/C++, otherwise he could be charged of cheating by using a more productive language :). Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Python vs C for a mail server
Jens Theisen wrote: > Please don't be offended, but if anyone could make a point of how Python's > disadvantages in these regards could be alleviated, I'd be very > interested. > > Jens Well, I write Java, C++ and Python code, and I have posted a few thoughts about this on my blog : http://nicolas.lehuen.com/ My two latest problems with coding in C++ are due to the environments : libraries using different string types and the whole problem with the building system. I love the language, but I get a much better leverage through Python and Java due to the quality and ease of use of their built-in and third party libraries. I use C++ only for my core data structure (namely a tuned version of a ternary search tree which I use to build full text indices). Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Make staticmethod objects callable?
Hi everyone, I was wondering if it would make sense to make staticmethod objects callable, so that the following code would work: class A: @staticmethod def foo(): pass bar = foo() I understand staticmethod objects don't need to implement __call__ for their other use cases, but would it still make sense to implement __call__ for that specific use case? Would it be error-prone in any way? Thx and regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Make staticmethod objects callable?
Felipe Almeida Lessa wrote: > Em Ter, 2006-02-28 às 15:17 -0500, Nicolas Fleury escreveu: > >>class A: >> @staticmethod >> def foo(): pass >> bar = foo() > > > # Why not: > > def foo(): pass > > class A: > bar = foo() > foo = staticmethod(foo) > Well, you could even do: class A: def foo(): pass bar = foo() staticmethod(foo) But it's a bit sad to have a special syntax for decorators then. It's a usability problem, nothing to do with functionality. There's obvious workarounds, but IMHO any user saying "it should just work" is at least partly right. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Make staticmethod objects callable?
Steven Bethard wrote: > Nicolas Fleury wrote: > >> I was wondering if it would make sense to make staticmethod objects >> callable, so that the following code would work: >> >> class A: >> @staticmethod >> def foo(): pass >> bar = foo() > > Do you have a real-world use case? I pretty much never use > staticmethods (preferring instead to use module-level functions) so I'm > having a hard time coming up with some code where this would be really > useful. I'm also a little wary of breaking the parallel between > classmethod and staticmethod which are currently *just* descriptors > (without any other special functionality). Well, IMHO, if staticmethod is worth being standard, than calling these static methods inside the class definition is worth being supported. To be honest I don't use static methods like you, but users come see me asking "Why?" and I find their code logically structured so I conclude there's a usability problem here. > Maybe instead of making just staticmethods callable, both staticmethods > and classmethods could gain an 'im_func' attribute like bound and > unbound methods have? I don't like it either (__get__ can be called anyway). My problem is the expectation of the user. I wonder if it should just work. Adding a few lines of code in staticmethod is worth it if it avoids all these questions over and over again, no? Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: Make staticmethod objects callable?
Steven Bethard wrote: > ... > Yes, you have to explain descriptors, but at the point that you start > trying to do funny things with staticmethods and classmethods, I think > you need to start learning about them anyway.) That's all good points, but IMHO, descriptors are a much more advanced Python feature than static methods, especially for programmers from other backgrounds, like Java/C#/C++. We basically have the choice between hiding something unnecessarily complex or force to understand a useful feature;) > All that said, you should probably just submit a patch and see what > happens. I'll make a brief comment on it along the above lines, but > since I'm not a committer, it's not really worth your time to try to > convince me. ;) I might do it, but even if I'm not a commiter, I'll continue trying to convince myself;) Nicolas -- http://mail.python.org/mailman/listinfo/python-list
wxpython and wxtextctrl
Hello, my script worked well until today : when I tried to launch it, I got the following : frame = MyFrame(None,-1,"Geometrie",size=wx.Size(600,400)) File "/home/nico/Desktop/wxGeometrie/version 0.73/geometrie.py", line 74, in __init__ self.commande.Bind(wx.EVT_CHAR, self.EvtChar) AttributeError: wxTextCtrl instance has no attribute 'Bind' (self.commande is a wxTextCtrl instance) I don't understand : why did wxTextCtrl lost its Bind attribute ?? As there's not so much changes on my computer since yesterday, I suppose this is due to Boa package installation on my Ubuntu Hoary ? Does Boa installation changes wxpython version ? Is wxTextCtrl attribute .Bind() obsolete ?? Thanks, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: wxpython and wxtextctrl
Ok, as I guessed, it was Boa installation which changed the wxpython version used. I removed Boa... Thanks ! Nicolas Greg Krohn a écrit : > Nicolas Pourcelot wrote: > >> Hello, >> my script worked well until today : when I tried to launch it, I got >> the following : >> >> frame = MyFrame(None,-1,"Geometrie",size=wx.Size(600,400)) >> File "/home/nico/Desktop/wxGeometrie/version 0.73/geometrie.py", >> line 74, in __init__ >> self.commande.Bind(wx.EVT_CHAR, self.EvtChar) >> AttributeError: wxTextCtrl instance has no attribute 'Bind' >> >> (self.commande is a wxTextCtrl instance) >> I don't understand : why did wxTextCtrl lost its Bind attribute ?? >> As there's not so much changes on my computer since yesterday, I >> suppose this is due to Boa package installation on my Ubuntu Hoary ? >> Does Boa installation changes wxpython version ? >> Is wxTextCtrl attribute .Bind() obsolete ?? >> >> Thanks, >> Nicolas > > > control.Bind is relativly new. The wxTextCtrl notation (vs wx.TextCtrl) is > the old way (but it IS kept around for backwards compatablility). My guess > is that your code is for for a newer version of wxPython than what you > actually have. > > Try printing the version from in your code: > > import wxPyhon > print wxPython.__version__ > self.commande.Bind(wx.EVT_CHAR, self.EvtChar) > > -greg > -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing 2 similar strings?
William Park a écrit : > How do you compare 2 strings, and determine how much they are "close" to > each other? Eg. > aqwerty > qwertyb > are similar to each other, except for first/last char. But, how do I > quantify that? > > I guess you can say for the above 2 strings that > - at max, 6 chars out of 7 are same sequence --> 85% max > > But, for > qawerty > qwerbty > max correlation is > - 3 chars out of 7 are the same sequence --> 42% max > > (Crossposted to 3 of my favourite newsgroup.) Hi, If you want to use phonetic comparison, here are some algorithms that are reportedly more efficient than Soundex : Double-Metaphone NYSIIS Phonex Of course, phonetic algorithms have a lot of disadvantages, the main one being that they know about one way to pronounce words (usually a rather rigid, anglo-saxon way) which may not be the right way (hence the examples given before for Gaellic surnames). But these ones are far "better" than soundex. Regards, Nicolas Lehuen -- http://mail.python.org/mailman/listinfo/python-list
Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Guido van Rossum wrote: > After many rounds of discussion on python-dev, I'm inviting public > comments for PEP 343. Rather than posting the entire PEP text here, > I'm inviting everyone to read it on line > (http://www.python.org/peps/pep-0343.html) and then post comments on a > Wiki page I've created for this purpose > (http://wiki.python.org/moin/WithStatement). > > I think this is a good one; I hope people agree. Its acceptance will > obsolete about 4 other PEPs! (A sign that it fulfills a need and that > the proposed solution is powerful.) I like the PEP very much; I guess most C++ programmers are missing that capability in Python. (I was following the discussion on python-dev, and I'm pleased and surprised how good the result/compromise is). What about making the ':' optional (and end implicitly at end of current block) to avoid over-indentation? def foo(): with locking(someMutex) with opening(readFilename) as input with opening(writeFilename) as output ... would be equivalent to: def foo(): with locking(someMutex) with opening(readFilename) as input with opening(writeFilename) as output ... Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Andrew Dalke wrote: >>def foo(): >> with locking(someMutex) >> with opening(readFilename) as input >> with opening(writeFilename) as output >> ... > > > Nothing in Python ends at the end of the current block. > They only end with the scope exits. The order of deletion > is not defined, and you would change that as well. There's no change in order of deletion, it's just about defining the order of calls to __exit__, and they are exactly the same. As far as I know, PEP343 has nothing to do with order of deletion, which is still implementation-dependant. It's not a constructor/destructor thing like in C++ RAII, but __enter__/__exit__. But yes, it creates a precedent by creating a statement affecting the end of the current indentation block. But that's what this PEP is all about... > Your approach wouldn't allow the following No, I said making the ':' *optional*. I totally agree supporting ':' is useful. > If the number of blocks is a problem it wouldn't be that > hard to do > > with multi( locking(someMutex), > opening(readFilename), > opening(writeFilename) ) as _, input, output: > ... True. But does it look as good? Particularly the _ part? Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Andrew Dalke wrote:
> The implementation would need to track all the with/as forms
> in a block so they can be __exit__()ed as appropriate. In this
> case ghi.__exit() is called after jkl.__exit__() and
> before defg.__exit__
>
> The PEP gives an easy-to-understand mapping from the proposed
> change to how it could be implemented by hand in the existing
> Python. Can you do the same?
I think it is simple and that the implementation is as much
straight-forward. Think about it, it just means that:
> with abc
>
> with defg:
> with ghi
> with jkl:
> 1/0
is equivalent to:
> with abc:
>
> with defg:
> with ghi:
> with jkl:
> 1/0
That's it. Nothing more complex. It's only about syntax.
> I have not idea if the problem you propose (multiple with/as
> blocks) will even exist so I can't comment on which solution
> looks good. It may not be a problem in real code, so not needing
> any solution.
Good point. As a C++ programmer, I use RAII a lot. However, there's
situations in C++ that don't apply, like allocating dynamic memory in a
scope. However, I still expect some Python programmers to use it enough
to ask for that syntax to be added, in the same way operators like +=
have been added.
But there's another point that has nothing to do with how many "with"
statements you have in a function. In C++, very very rarely I've seen
something like:
void foo() {
{ // (define a scope for the Lock object)
Lock locking(myMutex);
...
}
...
{
Lock locking(myMutex);
...
}
}
So I come to another conclusion: the indentation syntax will most of the
time result in a waste of space. Typically a programmer would want its
with-block to end at the end of the current block.
So basically, there's two 10-90% points, one in favor of my proposal,
one against:
- Most of the time, you don't have a lot of with-statements in a single
function, so not so much indentation.
- Most of the time, a with-statement ends at the end of current block,
so indentation-syntax most of the time result in a waste of space.
The way to see my proposal is not "to be used when you have multiple
with-blocks" but instead "never use the ':' syntax, unless necessary".
The day some code need it, it's very easy to add a ':' and indent some
code with our favorite editor.
Regards,
Nicolas
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Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Ilpo Nyyssönen wrote: > Nicolas Fleury <[EMAIL PROTECTED]> writes: >>What about making the ':' optional (and end implicitly at end of current >>block) to avoid over-indentation? >> >>def foo(): >>with locking(someMutex) >>with opening(readFilename) as input >>with opening(writeFilename) as output >>... > > > How about this instead: > > with locking(mutex), opening(readfile) as input: > ... > > So there could be more than one expression in one with. I prefer the optional-indentation syntax. The reason is simple (see my discussion with Andrew), most of the time the indentation is useless, even if you don't have multiple with-statements. So in my day-to-day work, I would prefer to write: def getFirstLine(filename): with opening(filename) as file return file.readline() than: def getFirstLine(filename): with opening(filename) as file: return file.readline() But I agree that in the case of only one with-statement, that's no big deal. Also, if multiple with-statements are separated by other indentating statements, your proposal doesn't help: with locking(lock) if condition: with opening(filename) as file for line in file: ... would still be needed to be written: with locking(lock): if condition: with opening(filename) as file: for line in file: ... Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Andrew Dalke wrote:
> Consider the following
>
> server = open_server_connection()
> with abc(server)
> with server.lock()
> do_something(server)
>
> server.close()
>
> it would be translated to
>
> server = open_server_connection()
> with abc(server):
> with server.lock()
> do_something(server)
> server.close()
>
> when I meant for the first code example to be implemented
> like this
>
> server = open_server_connection()
> with abc(server):
> with server.lock()
> do_something(server)
>
> server.close()
That's an interesting point. But I'm not sure if it is a realistic
error. It would be like using a with-statement without knowing what it
does. Also, and it seems we agree, these cases are very rare.
>
> (It should probably use the with-block to handle the server open
> and close, but that's due to my lack of imagination in coming up
> with a decent example.)
>
> Because of the implicit indentation it isn't easy to see that
> the "server.close()" is in an inner block and not at the outer
> one that it appears to be in. To understand the true scoping
> a reader would need to scan the code for 'with' lines, rather
> than just looking at the layout.
But with both syntaxes you only look at the indentation layout, no? If
you want to know the "scope" of something as you said, it means you have
already scan its "with" statement. You only need after that to look at
the indentation layout, as with indentation syntax.
It's however less obvious at first look that with-statements implies
some scope, but I feel that Python newcomers usually do the opposite
error instead, thinking their variables have a defined scope as in some
other languages.
> A test for how often this is needed would be to look in existing
> code for the number of try/finally blocks. I have seen and
> written some gnarly deeply stacked blocks but not often - once
> a year?
>
> That's not to say it's a good indicator. A lot of existing code
> looks like this
I agree. It's hard to find a good indicator. In my case I use both my
Python code (with try/finally typically ending a function) and my C++
code (with typically no {} block created for RAII object scope). So, my
conclusion, most of the time the indentation will be useless.
> What I mean by all of this is that the new PEP may encourage
> more people to use indented blocks, in a way that can't be
> inferred by simply looking at existing code. In that case
> your proposal, or the one written
Totally agree. The with-statement will open the door to new programming
patterns in Python and it's hard to tell from status quo how much it
will be used.
Regards,
Nicolas
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Re: For review: PEP 343: Anonymous Block Redux and Generator Enhancements
Steven Bethard wrote: > Can you do the same thing for your proposal? As I understand it you > want some sort of implicitly-defined BLOCK that starts the line after > the with statement and runs to the end of the current block... Yes. I totally agree with the syntax in the PEP, it provides a necessary feature. I'm just suggesting to make the indentation *optional*, because most of the time it is not necessary. > Do you think the benefit of less indentation outweighs the added > complexity of explaining the construct? I still can't think of a good > way of explaining the semantics you want. If you could provide an > explanation that's simple and as explicit as Guido's explanation in PEP > 343, I think that would help your case a lot. Since the current syntax would be there, the no-indentation syntax can be explained in terms of the indentation syntax: """ To avoid over-indentation, a with-statement can avoid defining a new indentation block. In that case, the end of the with block is the end of the current indentation block. with EXPR as VAR REST OF BLOCK is equivalent to with EXPR as VAR: BLOCK """ What do you think? I fail to see the complexity... > P.S. I think it's a great sign that people are mainly squabbling about > syntax here. More likely than not, Guido's already made his mind up > about the syntax. So, since no one seems to have any real problems with > the semantics, I'm hopeful that we'll get a direct implementation of PEP > 343 in the next Python release. =) It's important to note that nobody is against the PEP syntax. We are only talking about adding things to it (optional indentation, or multiple-as as with import). All these changes can also be made later, so no proposition should slow down the implementation of the PEP. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: For review: PEP 343: Anonymous Block Redux and GeneratorEnhancements
Delaney, Timothy C (Timothy) wrote: > Nicolas Fleury wrote: >>def getFirstLine(filename): >> with opening(filename) as file >> return file.readline() > > Your tastes definitely disagree with the majority of Python programmers > then, including Guido. Scoping is defined in Python by indentation. I'm very happy to met someone who can speak for the majority of Python programmers, I should have chat with you in the first place;) But you're right, that would make a precedent in Python, and that is probably what makes my proposal so bad. Someone could argue that this should be allowed too: with locking(lock) if condition with opening(filename) as file for line in file ... And that's horrible IMO (and a no-no to me). About the majority of Python programmers, a lot of newcomers come from languages where you don't have to make a new block for an acquire/release pattern. Also, the following syntax: decorate staticmethod: def foo(): ... have been rejected for decorators. All this to say that over-indentation can be an issue. > If you want the above sort of thing, you're going to have to write a new > PEP, and I'd be very surprised to see it accepted. But there's nothing > stopping you from doing so. > > >>def getFirstLine(filename): >> with opening(filename) as file: >> return file.readline() > > This is beautiful and explicit. What else could you want? Did you deliberately keep that example instead of the other one in the message? with locking(lock): if condition: with opening(filename) as file: for line in file: ... It is definately explicit, but beautiful? Add to that the indentation of the class, of the method, a few more with-statements and you end up with something that makes it difficult to respect PEP008 (4 spaces indentation and lines < than 80). Compare that with the += like operators. It is not beautiful, but very usable. The same can be said for @decorators. > The syntax: > > with EXPR1 as VAR1, EXPR2 as VAR2: > ... That syntax doesn't help in the previous example. > was discussed on python-dev. It wasn't explicitly rejected, but the > feeling seemed to be that it was an unnecessary complication as far as > PEP 343 is concerned. There's nothing stopping another PEP proposing > this as an extension to PEP 343, and there's nothing stopping that being > in Python 2.5 if it's accepted. I totally agree. I don't want to change PEP343, but keeping the door open for a no-indentation syntax is a good idea. > PEP 343 was originally PEP 340 (and several other things) and was quite > complicated at one point (it originally contained PEP 342 as well). The > PEP in its current state represents 2 months of discussion, complication > and (finally) simplification. Its semantics are clear and unambiguous. > And (as Guido states) it will obsolete 4(?) other PEPs. I know, and I followed these discussions even in vacation. I'm very happy with the result. I'm just pointing that it will result in over-indented code. In some situations indentation is necessary anyway, so the PEP syntax is fine. Will I write a PEP for that? Maybe. I think the first step is to just use with-statements in real-life code and see how it comes. But I will not be surprised if it is added someday. Regards, Nicolas -- http://mail.python.org/mailman/listinfo/python-list
Re: "also" to balance "else" ?
Ron Adam wrote:
> It occurred to me (a few weeks ago while trying to find the best way to
> form a if-elif-else block, that on a very general level, an 'also'
> statement might be useful. So I was wondering what others would think
> of it.
But the feature is already there:
for x in :
BLOCK1
if :
ALSO-BLOCK
break
else:
BLOCK2
If find "else" fine, since the only times I used it is in searches:
for x in
BLOCK1
if : break
else:
raise Exception('Not found')
In that case, 'else' sounds like the good keyword.
Regards,
Nicolas
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strxfrm works with unicode string ?
I am trying to use strxfm with unicode strings, but it does not work. This is what I did: >>> import locale >>> s=u'\u00e9' >>> print s é >>> locale.setlocale(locale.LC_ALL, '') 'French_Switzerland.1252' >>> locale.strxfrm(s) Traceback (most recent call last): File "", line 1, in -toplevel- locale.strxfrm(s) UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 0: ordinal not in range(128) >>> Someone sees what I did wrong ? -- http://mail.python.org/mailman/listinfo/python-list
Re: strxfrm works with unicode string ?
Gruëzi, Gerald ;-) Well, ok, but I don't understand why I should first convert a pure unicode string into a byte string. The encoding ( here, latin-1) seems an arbitrary choice. Your solution works, but is it a workaround or the real way to use strxfrm ? It seems a little artificial to me, but perhaps I haven't understood something ... Does this mean that you cannot pass a unicode string to strxfrm ? Bonne journée ! -- http://mail.python.org/mailman/listinfo/python-list
Re: python in academics?
2007/11/6, Nicolas.Chauvat <[EMAIL PROTECTED]>: > > Le Mon, 29 Oct 2007 20:39:29 -0700, sandipm a écrit: > > > seeing posts from students on group. I am curious to know, Do they teach > > python in academic courses in universities? > > I am teaching assistant for the course > > http://www.etudes.ecp.fr/cours/claroline/course/index.php?cid=TI1210 > > held at http://www.ecp.fr/index_html_en > > They are also making an increasing use of python over there. Python is also taught at the university of Calais (France). A master about free software opened last year. http://dpt-info.univ-littoral.fr/mediawiki/index.php/I2L:Accueil -- > http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Pythonic way to determine if one char of many in a string
* [email protected] [2009-02-16 00:17:37 -0500]: > I need to test strings to determine if one of a list of chars is > in the string. A simple example would be to test strings to > determine if they have a vowel (aeiouAEIOU) present. > I was hopeful that there was a built-in method that operated > similar to startswith where I could pass a tuple of chars to be > tested, but I could not find such a method. > Which of the following techniques is most Pythonic or are there > better ways to perform this type of match? > # long and hard coded but short circuits as soon as match found > if 'a' in word or 'e' in word or 'i' in word or 'u' in word or > ... : > -OR- > # flexible, but no short circuit on first match > if [ char for char in word if char in 'aeiouAEIOU' ]: > -OR- > # flexible, but no short circuit on first match > if set( word ).intersection( 'aeiouAEIOU' ): I would go for something like: for char in word: if char in 'aeiouAEIUO': char_found = True break else: char_found = False (No, I did not forget to indent the else statement, see http://docs.python.org/reference/compound_stmts.html#for) It is clear (imo), and it is seems to be the intended idiom for a search loop, that short-circuits as soon as a match is found. Cheers, -- Nicolas Dandrimont linux: the choice of a GNU generation ([email protected] put this on Tshirts in '93) signature.asc Description: Digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Pythonic way to determine if one char of many in a string
* [email protected] [2009-02-16 00:48:34 -0500]: > Nicolas, > > > I would go for something like: > > > > for char in word: > > if char in 'aeiouAEIUO': > > char_found = True > > break > > else: > > char_found = False > > > > It is clear (imo), and it is seems to be the intended idiom for a > > search loop, that short-circuits as soon as a match is found. > > Thank you - that looks much better that my overly complicated attempts. > > Are there any reasons why I couldn't simplify your approach as follows? > > for char in word: > if char in 'aeiouAEIUO': > return True > return False If you want to put this in its own function, this seems to be the way to go. Cheers, -- Nicolas Dandrimont The nice thing about Windows is - It does not just crash, it displays a dialog box and lets you press 'OK' first. (Arno Schaefer's .sig) signature.asc Description: Digital signature -- http://mail.python.org/mailman/listinfo/python-list
