Re: Why bool( object )?

[Aaron Brady]

On Apr 28, 1:35 am, Lie Ryan  wrote:
> Aaron Brady wrote:
> > What is the rationale for considering all instances true of a user-
> > defined type?  
>
> User-defined objects (or type) can override .__len__() [usually
> container types] or .__nonzero__() to make bool() returns False.
>
> > Is it strictly a practical stipulation, or is there
> > something conceptually true about objects?
>
> Objects are true unless they define themself as false. The practical
> implication is we can do this:
>
> def foo(args = None):
>      if args:
>          ...
>
> In python all objects are true except: None, False, 0/0L/0.0/0j, empty
> sequence or container, and on objects that defines .__len__() or
> .__nonzero__() that returns 0 or False.
>
>
>
> > '''
> > object.__bool__(self)
> > If a class defines neither __len__() nor __bool__(), all its instances
> > are considered true.
> > '''
>
> > This makes it so all objects except False, None, 0, and empty
> > containers are true by default.  I am not convinced that 'if  > generic object>' should have any meaning; it should probably throw an
> > exception.  Is it part of Python's look and feel or its mentality?  Is
> > it part of the Zen?  Certainly other ideal types can't be cast from
> > generic objects, so why booleans?  Is it an ineffable component of the
> > author's vision for the language?  I think that giving arbitrary
> > syntactic constructs meaning is just space-filler.  It's worse than
> > syntactic sugar, it's semantic sugar.  Why not assign meanings willy-
> > nilly to other random juxtapositions of tokens?
>
> It's part of the design decision. In almost all cases (in any language),
> a so-called "Design Decision" is rather random and prone to subjective
> judgment, just as the decision to make bool(int) returns False only on
> 0, -1, or for all negative values; whether to make bool(100) and
> exception or True; or round() rounds down or up or even-odd; or the use
> of brackets vs. indentation; or whether to treat empty list as True or
> False.

Whether it's a good feature and whether it's a popular feature are two
different things.  (It's not always clear that the former is even real
anyway.)

I'm actually not sure that my question was /entirely/ scientifically
motivated.  Perhaps I'm expressing admiration (or maybe envy).  Maybe
I want to design a popular language too.

If I was really being scientific, I would have been wondering, what is
the balance of pros and cons of the decision?  pros - cons = ?  Is
that an objective expression?  Are there only measurable quantities in
both operands?  If it's a close call, I might not agree, or might not
have followed the same experimental method.

Trivially the answer is, 'the decision maker found sum( pros ) > sum
( cons )'.  Many arts and disciplines do guesswork to a degree in
evaluating their 'sum( pros )', so perhaps I should expect a degree of
variation in what the experts all say that quantity is.

On a more idealist's level, perhaps I am asking the outside world
what /my/ evaluation of 'sum( pros )' is.  What's yours?

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Re: Web based application development using python

[Tim Hoffman]

Calling mod_python a web framework is a bit of a stretch.

if you want to work at that level though mod_wsgi is worth a look,

on top of that you can put a range of frameworks such as
repose, django, turbo gears etc..

T


On Apr 28, 12:55 pm, Rahul  wrote:
> > > 2) I have my web based application written using mod_python
> > > a. It should be more based on framework type.
> > > b. It should have all the features present in mod_python.
>
> > These two goals conflict.  You'll need to use your brain to discover
> > what is best for your application.  In general "have all the features
> > of" and "but better" conflict.
>
> > --Scott David Daniels
> > scott.dani...@acm.org
>
> hi scott,
>
> i am getting more specific, is there any web development framework
> better than mod python which is
> easy to maintain.
>
> thanks
>
> rahul

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Re: Web based application development using python

[Rahul]

1) Do you have any idea about web based support (like mod_python)
provided by python.org (official web site)

Details: - As we know mod_python is used for embeding python code into
apache server.
so, i want to know whether mod_python is officially supported by
python.org or if there is
other such framework for embeding python on web server

Thanks,

Rahul
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Re: python segfaulting, MemoryError (PyQt)

[Diez B. Roggisch]

Denis L schrieb:

Hello,

I'm experiencing odd errors on both windows and linux with the following 
code:


import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Options(QDialog):
def __init__(self, values):
QDialog.__init__(self)

self.values = values

fooEdit = QLineEdit(values['foo'])
self.connect(fooEdit, SIGNAL('textChanged(QString)'),
 lambda value: self.optionChanged('foo', value))

barEdit = QLineEdit(values['bar'])
self.connect(barEdit, SIGNAL('textChanged(QString)'),
 lambda value: self.optionChanged('bar', value))

layout = QVBoxLayout()
layout.addWidget(fooEdit)
layout.addWidget(barEdit)

self.setLayout(layout)

def optionChanged(self, option, value):
self.values[option] = value
print self.values

def main(args):
app = QApplication(args)
values = dict(foo='', bar='')
dialog = Options(values)
dialog.show()
app.exec_()

if __name__ == '__main__':
main(sys.argv)


If I type a character in fooEdit, another character in barEdit, and then 
delete the character from barEdit I get an unhandled win32 exception occured 
in python.exe on windows and segfault on linux.


If I type a character in fooEdit, delete it, and then type a character in 
barEdit I get:


{'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
{'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
{'foo': Traceback (most recent call last):
  File "L:\home\dev\python\test.py", line 17, in 
lambda value: self.optionChanged('bar', value))
  File "L:\home\dev\python\test.py", line 27, in optionChanged
print self.values
MemoryError

I'm using Python 2.5.4 and PyQt 4.4.3-1


As the documentation of pyqt clearly states, connecting signals doesn't 
increment the refcount on a passed slot, thus

 you need to keep a reference to your slots around.

Diez
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Re: Why bool( object )?

[Steven D'Aprano]

On Mon, 27 Apr 2009 23:11:11 -0700, Aaron Brady wrote:

> What is the rationale for considering all instances true of a user-
> defined type?  Is it strictly a practical stipulation, or is there
> something conceptually true about objects?

Seven years ago, in an attempt to convince Guido *not* to include 
booleans in Python, Laura Creighton wrote a long, detailed post 
explaining her opposition.

At the heart of her argument is the observation that Python didn't need 
booleans, at least not the ints-in-fancy-hats booleans that we've ended 
up with, because Python already made a far more useful and fundamental 
distinction: between Something and Nothing.

http://groups.google.com/group/comp.lang.python/msg/2de5e1c8384c0360?hl=en

All objects are either Something or Nothing. The instances of some 
classes are always Something, just as the instances of some classes are 
always Nothing. By default, instances are Something, unless __nonzero__ 
returns False, or __len__ returns 0, then they are Nothing.

In a boolean (or truth) context, Something and Nothing behave like True 
and False in languages with real booleans:

if obj:
print "I am Something"
else:
print "I am Nothing"


To steal an idiom from Laura: Python has a float-shaped Nothing 0.0, a 
list-shaped Nothing [], a dict-shaped Nothing {}, an int-shaped Nothing 
0, a singleton Nothing None, and so forth. It also has many corresponding 
Somethings.

All bool() does is convert Something or Nothing into a canonical form, 
the subclassed ints True and False.

I'm not sure whether Guido ever used the terms Something vs Nothing when 
describing Python's truth-testing model, but it is clearly there, at the 
heart of Python. Python didn't even get a boolean type until version 2.3.




-- 
Steven
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Web framework for embedded system

[Thomas Heller]

I'm looking for a lightweight web-framework for an embedded system.
The system is running a realtime linux-variant on a 200 MHz ARM
processor, Python reports a performance of around 500 pystones.

The web application will not be too fancy, no databases involved
for example, but it will need to control some simple peripherals
(some parallel in/out, some dacs) attached to the system.

It should provide a user interface showing the current state and
allowing to manipulate it via a browser, and I will probably need
to support some rpc as well.

Does this sound sensible at all? Any suggestions?

Thomas
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sorted() erraticly fails to sort string numbers

[uuid]

I would be very interested in a logical explanation why this happens on 
python 2.5.1:


In order to sort an etree by the .text value of one child, I adapted 
this snippet from effbot.org:



import xml.etree.ElementTree as ET

tree = ET.parse("data.xml")

def getkey(elem):
return elem.findtext("number")

container = tree.find("entries")

container[:] = sorted(container, key=getkey)

tree.write("new-data.xml")


While working with a moderately sized xml file (2500 entries to sort 
by), I found that a few elements were not in order. It seems that 
numbers with seven digits were sorted correctly, while those with six 
digits were just added at the end.


I fixed the problem by converting the numbers to int in the callback:


def getkey(elem):
return int(elem.findtext("number"))


So to my naive mind, it seems as if there was some error with the 
sorted() function. Would anyone be as kind as to explain why it could 
be happening? Thanks in advance!


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Re: Presentation software for Python code

[John Reid]

Neal Becker wrote:

IPython offers something similar for giving demos. I've found that very
useful in the past.


Really?  Any pointers?


http://ipython.scipy.org/doc/manual/html/api/generated/IPython.demo.html

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Re: sorted() erraticly fails to sort string numbers

[Andre Engels]

On Tue, Apr 28, 2009 at 9:47 AM, uuid  wrote:
> I would be very interested in a logical explanation why this happens on
> python 2.5.1:
>
> In order to sort an etree by the .text value of one child, I adapted this
> snippet from effbot.org:
>
>> import xml.etree.ElementTree as ET
>>
>> tree = ET.parse("data.xml")
>>
>> def getkey(elem):
>>    return elem.findtext("number")
>>
>> container = tree.find("entries")
>>
>> container[:] = sorted(container, key=getkey)
>>
>> tree.write("new-data.xml")
>
> While working with a moderately sized xml file (2500 entries to sort by), I
> found that a few elements were not in order. It seems that numbers with
> seven digits were sorted correctly, while those with six digits were just
> added at the end.
>
> I fixed the problem by converting the numbers to int in the callback:
>
>> def getkey(elem):
>>    return int(elem.findtext("number"))
>
> So to my naive mind, it seems as if there was some error with the sorted()
> function. Would anyone be as kind as to explain why it could be happening?
> Thanks in advance!

When sorting strings, including strings that represent numbers,
sorting is done alphabetically. In this alphabetical order the numbers
are all ordered the normal way, so two numbers with the same number of
digits will be sorted the same way, but any number starting with "1"
will come before any number starting with "2", whether they denote
units, tens, hundreds or millions. Thus:

"1" < "15999" < "16" < "2"




-- 
André Engels, andreeng...@gmail.com
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Memory leak on python 2.5 if using str(dict(a='a'))

[Benjamin Liu]

Hi, all.

I use guppy-pe to identify this issue in my program. The resources links are 
all embedded in source code already.

I developed a test case for your convenience and attached the log. Any gurus 
help out here? It's really python internal stuff which I can't easily peek into.

Thanks,
Benjamin

test_tuple_and_dict.py
Description: Binary data
>TEST4
{'a': 'a_value', 'b': 'b_value'}
Partition of a set of 5 objects. Total size = 1064 bytes.
 Index  Count   % Size   % Cumulative  % Kind (class / dict of class)
 0  2  40  864  81   864  81 types.FrameType
 1  1  20  136  13  1000  94 dict (no owner)
 2  1  20   32   3  1032  97 list
 3  1  20   32   3  1064 100 str
=0=

Set of 2  objects. Total size = 864 bytes.
 Index Size   %   Cumulative  %   Name at Address
 0  448  51.9   448  51.9 
 1  416  48.1   864 100.0 
--0--

=1=

Set of 1  object. Total size = 136 bytes.
 Index Size   %   Cumulative  %   Address*Length
 0  136 100.0   136 100.0 0x828b68c*1
--0--
{'Py_Repr': [{...}, [...]]}
=2=

Set of 1  object. Total size = 32 bytes.
 Index Size   %   Cumulative  %   Address*Length
 0   32 100.032 100.0 0x826b58c*0
--0--
[[...]]
=3=

Set of 1  object. Total size = 32 bytes.
 Index Size   %   Cumulative  %   Representation (limited)
 0   32 100.032 100.0 'Py_Repr'
--0--
Py_Repr
>TEST5
a a_value
b b_value
Partition of a set of 2 objects. Total size = 736 bytes.
 Index  Count   % Size   % Cumulative  % Kind (class / dict of class)
 0  2 100  736 100   736 100 types.FrameType
=0=

Set of 2  objects. Total size = 736 bytes.
 Index Size   %   Cumulative  %   Name at Address
 0  372  50.5   372  50.5 
 1  364  49.5   736 100.0 
--0--

>TEST6
Partition of a set of 2 objects. Total size = 864 bytes.
 Index  Count   % Size   % Cumulative  % Kind (class / dict of class)
 0  2 100  864 100   864 100 types.FrameType
=0=

Set of 2  objects. Total size = 864 bytes.
 Index Size   %   Cumulative  %   Name at Address
 0  448  51.9   448  51.9 
 1  416  48.1   864 100.0 
--0--

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Re: Web based application development using python

[Marco Mariani]

Rahul wrote:


1) Do you have any idea about web based support (like mod_python)
provided by python.org (official web site)

Details: - As we know mod_python is used for embeding python code into
apache server.
so, i want to know whether mod_python is officially supported by
python.org or if there is
other such framework for embeding python on web server



Forget about mod_python, everything else is better.

This list (the first result upon googling for "python web frameworks") 
is actually up to date, and a good start.


http://wiki.python.org/moin/WebFrameworks

Just don't ask which one is best for everything, or which one is The 
Official Standard Way Of Doing Things.


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Re: sorted() erraticly fails to sort string numbers

[uuid]

I am at the same time impressed with the concise answer and 
disheartened by my inability to see this myself.

My heartfelt thanks!


On 2009-04-28 10:06:24 +0200, Andre Engels  said:


When sorting strings, including strings that represent numbers,
sorting is done alphabetically. In this alphabetical order the numbers
are all ordered the normal way, so two numbers with the same number of
digits will be sorted the same way, but any number starting with "1"
will come before any number starting with "2", whether they denote
units, tens, hundreds or millions. Thus:

"1" < "15999" < "16" < "2"



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Re: python segfaulting, MemoryError (PyQt)

[Phil Thompson]

On Tue, 28 Apr 2009 03:53:34 +0200, "Denis L"  wrote:
> Hello,
> 
> I'm experiencing odd errors on both windows and linux with the following 
> code:
> 
> import sys
> from PyQt4.QtCore import *
> from PyQt4.QtGui import *
> 
> class Options(QDialog):
> def __init__(self, values):
> QDialog.__init__(self)
> 
> self.values = values
> 
> fooEdit = QLineEdit(values['foo'])
> self.connect(fooEdit, SIGNAL('textChanged(QString)'),
>  lambda value: self.optionChanged('foo', value))
> 
> barEdit = QLineEdit(values['bar'])
> self.connect(barEdit, SIGNAL('textChanged(QString)'),
>  lambda value: self.optionChanged('bar', value))
> 
> layout = QVBoxLayout()
> layout.addWidget(fooEdit)
> layout.addWidget(barEdit)
> 
> self.setLayout(layout)
> 
> def optionChanged(self, option, value):
> self.values[option] = value
> print self.values
> 
> def main(args):
> app = QApplication(args)
> values = dict(foo='', bar='')
> dialog = Options(values)
> dialog.show()
> app.exec_()
> 
> if __name__ == '__main__':
> main(sys.argv)
> 
> 
> If I type a character in fooEdit, another character in barEdit, and then 
> delete the character from barEdit I get an unhandled win32 exception
> occured 
> in python.exe on windows and segfault on linux.
> 
> If I type a character in fooEdit, delete it, and then type a character in

> barEdit I get:
> 
> {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
> {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
> {'foo': Traceback (most recent call last):
>   File "L:\home\dev\python\test.py", line 17, in 
> lambda value: self.optionChanged('bar', value))
>   File "L:\home\dev\python\test.py", line 27, in optionChanged
> print self.values
> MemoryError
> 
> I'm using Python 2.5.4 and PyQt 4.4.3-1
> 
> Thanks in advance for any help.

Works fine for me with current versions.

Phil
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Re: python segfaulting, MemoryError (PyQt)

[Phil Thompson]

On Tue, 28 Apr 2009 09:35:31 +0200, "Diez B. Roggisch"

wrote:
> Denis L schrieb:
>> Hello,
>> 
>> I'm experiencing odd errors on both windows and linux with the following

>> code:
>> 
>> import sys
>> from PyQt4.QtCore import *
>> from PyQt4.QtGui import *
>> 
>> class Options(QDialog):
>> def __init__(self, values):
>> QDialog.__init__(self)
>> 
>> self.values = values
>> 
>> fooEdit = QLineEdit(values['foo'])
>> self.connect(fooEdit, SIGNAL('textChanged(QString)'),
>>  lambda value: self.optionChanged('foo', value))
>> 
>> barEdit = QLineEdit(values['bar'])
>> self.connect(barEdit, SIGNAL('textChanged(QString)'),
>>  lambda value: self.optionChanged('bar', value))
>> 
>> layout = QVBoxLayout()
>> layout.addWidget(fooEdit)
>> layout.addWidget(barEdit)
>> 
>> self.setLayout(layout)
>> 
>> def optionChanged(self, option, value):
>> self.values[option] = value
>> print self.values
>> 
>> def main(args):
>> app = QApplication(args)
>> values = dict(foo='', bar='')
>> dialog = Options(values)
>> dialog.show()
>> app.exec_()
>> 
>> if __name__ == '__main__':
>> main(sys.argv)
>> 
>> 
>> If I type a character in fooEdit, another character in barEdit, and then

>> delete the character from barEdit I get an unhandled win32 exception
>> occured
>> in python.exe on windows and segfault on linux.
>> 
>> If I type a character in fooEdit, delete it, and then type a character
in
>>
>> barEdit I get:
>> 
>> {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
>> {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
>> {'foo': Traceback (most recent call last):
>>   File "L:\home\dev\python\test.py", line 17, in 
>> lambda value: self.optionChanged('bar', value))
>>   File "L:\home\dev\python\test.py", line 27, in optionChanged
>> print self.values
>> MemoryError
>> 
>> I'm using Python 2.5.4 and PyQt 4.4.3-1
> 
> As the documentation of pyqt clearly states, connecting signals doesn't 
> increment the refcount on a passed slot, thus
>   you need to keep a reference to your slots around.

But it does increase the refcount for lambda slots.

Phil
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Re: python setup ?

[Andreas Röhler]

Xavier Maillard wrote:
> Hi
>
>Xavier Maillard  writes:
>
>> I am starting to do some work with python. I am looking for
>> options/setups to introduce into my .emacs file to have the best
>> experience possible with this scripting language.
>>
>> Where should I start ?
>
>I personnaly use python-mode.el that is much better than python.el (that
>come with emacs).
>
> In what is it better ?
>
>I use also ipython as python shell that integrate fine in emacs.
>
> Phew, how many new dependances should I install in order to have
> something simple to use ? :) I thought python was something for
> beginners, it is not. I find it easier to play lisp...
>
>   Xavier
>   
Hi Xavier,

as its well known, you are not a beginner with Emacs,
please permit to take your comment as occasion:

Your question and experience with Emacs and Python
reflects IMHO some general strength and likewise
present limitation.

The strength is, clearly: with that many files out
there, that many people who wrote already something for
python, with some Emacs Lisp knowledge you'll be able
to install a reasonable environment.

OTOH: how many people did that already, spent hours to
collect and adapt utilities from the net? And
afterwards? If we take together all this time from
users configuring an python-environment, we could
probably get more useful results from it. So there is a
lose of time.

Can we do better? ... :)

One thing, thats to realize IMO: times are gone where
one person with some knowledge of a language may write
a mode and thats it. Even maintaining it alone seems to
surpass any personal capacity. If we want to keep path,
we have to establish developer-groups caring for a
language. That happened already with C-modes AFAIS. We
need that for any major language.

Concerning python, we have enough man-power to
perform excellent things. To the extent, user have to do
`M-x python,' and an environment with all up-to-date
debugging facilities gets installed.

No question its great whats done at

http://www.emacswiki.org/emacs/PythonMode

Emacswiki was helpful many times for me.

However, for pure development issues, designed
platforms like Launchpad seem more suitable for the
purpose for me. Beside excellent bazaar behind, lets mention
its email- and bugreport integration.

As it happens we have with Barry Warsaw not just an
experienced Emacs Lisper, but a python core developer
with its python-mode account: we should try our chance
to proceed with his gentle help occasionally.

AFAIS we need tailored accounts, where we maintain
flavours of possible environments, learning and lifting
from each other, enabling distributions to select and
pull for delivering.

So far

Andreas

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Re: Web framework for embedded system

[Gerhard Häring]

Thomas Heller wrote:
> I'm looking for a lightweight web-framework for an embedded system.
> The system is running a realtime linux-variant on a 200 MHz ARM
> processor, Python reports a performance of around 500 pystones.
> 
> The web application will not be too fancy, no databases involved
> for example, but it will need to control some simple peripherals
> (some parallel in/out, some dacs) attached to the system.
> 
> It should provide a user interface showing the current state and
> allowing to manipulate it via a browser, and I will probably need
> to support some rpc as well.
> 
> Does this sound sensible at all? Any suggestions?

I'd try first what I know best. In my case Django. Despite the
restricted hardware, it might just work fine because you'll only use a
tiny fraction of it.

If this doesn't work because of CPU or memory requirements, I'd next try
to build my own using components like

- CherryPy for the web server, it should also be able to handle your
(XML)RPC requirements
- some templating language like Mako (my favourite)

It doesn't sound like you need much more.

You could even build upon wsgiref, string.Template and the XMLRPC stuff
in the standard library, but that's for people who like tinkering ;-)

-- Gerhard

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Re: Lisp mentality vs. Python mentality

[Dan Sommers]

On Tue, 28 Apr 2009 02:00:22 -0300, namekuseijin wrote:

> Dan Sommers wrote:
>> On Mon, 27 Apr 2009 07:57:00 +0300, Ciprian Dorin, Craciun wrote:
>>> I agree with your opinion about keeping the abstraction layers
>>> shallow, but in my view high-order and helper functions do not
>>> comprise a new abstraction layer. For example in Lisp, using map,
>>> reduce (fold), or any other high-order function is just like using
>>> for, or while in a normal imperative language.
>> 
>> If I hit a call to map or to reduce, I've hit the bottom:  map and
>> reduce are defined by Lisp and not by the programmer.
> 
> You truly don't know Lisp.  *Everything* in Lisp can be _redefined_ and
> if you can't do something conveniently that way, you can use a _macro_
> to implement convenient new syntax for it.

Yes, I agree:  Python and Lisp are extremely dynamic languages.  I *can* 
redefine map, reduce, +, and other operators and functions, but I know 
better.  When is the last time you examined someone else's code, and 
asked them what their "map" function did (in Lisp or in Python)?





-- 
Dan Sommers   A death spiral goes clock-
   wise north of the equator.
Atoms are not things. -- Werner Heisenberg  -- Dilbert's PHB

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Re: Restart generator when it is exhausted.

[Chris Rebert]

On Tue, Apr 28, 2009 at 2:54 AM, Lacrima  wrote:
> Hello!
>
> I am quite new to Python and I have maybe simple (or maybe not)
> question.
>
> Is it possible to restart generator when it is exhausted?

No. You have to make a new instance of the generator.

> What should I do to get the initial state of g? So if I do again g.next
> () I receive 'a'.

g = (i for i in a) #that is, make a fresh generator instance

> If it is not possible what are common techniques to use iterator or
> generator objects that allow restarting when it is needed?

There's itertools.cycle() --
http://docs.python.org/library/itertools.html#itertools.cycle

Cheers,
Chris
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Re: mailbox.mbox.add() sets access time as well as modification time

[tinnews]

Lawrence D'Oliveiro  wrote:
> In message , Grant 
> Edwards wrote:
> 
> > On 2009-04-26, Lawrence D'Oliveiro 
> > wrote:
> >
> >> In message <_vqdnf6pny1gymzunz2dnuvz_qcdn...@posted.visi>, Grant Edwards
> >> wrote:
> >>
> >>> ... if one didn't care about backwards-compatiblity with old e-mail
> >>> apps, then one would use a less broken mailbox format like
> >>> maildir.
> >>
> >> It's only in the proprietary-software world that we need to worry about
> >> backward compatibility with old, obsolete software that the vendors
> >> cannot or will not fix. In the Free Software world, we fix the software
> >> to bring it up to date.
> > 
> > Who's "we"?  Are you volunteering to fix all of the MUAs and
> > MTAs out there that have mbox code in them that do follow the
> > rules to make them compatible with _one_ broken library module?
> 
> All the MUAs and MTAs I'm aware of that are worth bothering about have the 
> option to support maildir format these days.
> 
Yes, but as I explained earlier in this thread there are reasons why
one might want to stay with mbox.  I use mutt which can quite happily
cope with either mbox or maildir (and some other formats), it can even
work with a mix of mailbox types.

I've used mutt for several years now and have tried to move to maildir
more than once and have always returned to mbox because the
disadvantages of maildir outweigh the benefits (for me).  Currently I
run mutt on a remote server where I have to use maildir because their
file systems are mounted noatime.  I am moving to reading mail on my
own Linux box just because I want to get back to mbox, this python
issue is about the only thing I have to overcome before I have what I
want. 

-- 
Chris Green

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Using ascii numbers in regular expression

[jorma kala]

Hi,

How can I use the ascii number of a character in a regular expression
(module re) instead of the character itself?
Thanks very much
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screen scraping with Python?

[Meenakshi, Arun Kumar]

Hi Friends,

Please let me know whether VT100 (Screen scrapping)
emulation is possible or not. If screen scrapping / VT100 emulation is
possible, please let me know how to do it. I will be happier, if you can
provide me steps and sample codes. I am a beginner in python. So kindly
help me by letting me know about the possibilities. EXPECTING THE REPLY
MAIL Thanks

 

Regards,

Arun

FoneNet : 390-13359

Mobile: 9884471702

 


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suggestion on a complicated inter-process communication

[Way]

Hello friends,

I have a little messy situation on IPC. Please if you can, give me
some suggestion on how to implement. Thanks a lot!

-> denotes create


MainProcess -> Process1 -> Process3 (from os.system)
   |
-> Process2 (from os.system) -> Process4 (from
os.system) ->Process5

I would like to make the communication between Process1 and Process5.
Process1 needs Process5's output to provide argument to generate
Process3, and in turn Process5 needs to wait Process3 finished.

Thank you very much if you can give a hint.

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Re: python segfaulting, MemoryError (PyQt)

[Phil Thompson]

On Tue, 28 Apr 2009 11:18:31 +0200, "Diez B. Roggisch"

wrote:
>>> As the documentation of pyqt clearly states, connecting signals doesn't
>>> increment the refcount on a passed slot, thus
>>>   you need to keep a reference to your slots around.
>> 
>> But it does increase the refcount for lambda slots.
> 
> Has that changed? It has been a while, but I've been bitten by this
before,
> so I was pretty sure about my answer.

Support for lambda slots was add in PyQt v4.1.1 (released December 2006).

Phil
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desperately looking for a howto on running my wxPython app on Vista

[Paul Sijben]

python 2.6, py2exe and Vista do not make a happy set.

Unfortunately I am in dire need to launch my app not only on WinXP but
also on Vista. I need 2.6 because of a number of support packages I am
using and some of which I am compiling myself (and python 2.5 needs a
version of visual studio that is no longer available.)

I can find all kinds of advice and discussions with google but I have
yet to find a clear explanation on what a poor developer like me is
supposed to do to get my python 2.6.2 , stackless, wxpython and all my
(self-built) pyds to work happily on Vista.

I am currently stuck on the infamous R6034 error but I understand that
after that there may be another issue with certain wxPython functions.

Can someone please point me to a howto on crafting the right Setup.py
and manifests etc. to make this work?

Paul
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Python 2.6 ImportError: cannot import name SSLType

[zerosumgame]

I have built python 2.6.1 and 2.6.2 with ssl support (Redhat 3.4.6-9 /
Openssl 0.9.8j).

I am trying to use this with the Apache Qpid project but cannot bring
up an ssl connection because the code relies on socket.SSLType which
is missing from my build.  The only references to SSLType I can find
for python is that it is missing from the windows version which I am
not using.

I do not see what is going wrong.

Any tips greatly appreciated.

Roger
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Re: screen scraping with Python?

[David Lyon]

On Mon, 27 Apr 2009 12:28:31 +0530, "Meenakshi, Arun Kumar"
 wrote:
> Hi Friends,
> 
> Please let me know whether VT100 (Screen scrapping)
> emulation is possible or not. If screen scrapping / VT100 emulation is
> possible, please let me know how to do it. I will be happier, if you can
> provide me steps and sample codes. I am a beginner in python. So kindly
> help me by letting me know about the possibilities. EXPECTING THE REPLY
> MAIL Thanks

Of course...

VT-100 terminals were usually rs-232 devices connected at 9600 baud

If you can write some python code talking to the serial port, you can
easily read the data from the port... render it... and do whatever you
need...

If you are doing it over a network then you are using a terminal emulator.

Many of the top name termninal emulators provide a programming api.

If not.. go open source

There are just many.. many different ways these days... depending on
what platform and which terminal emulator you are using...

David

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Restart generator when it is exhausted.

[Lacrima]

Hello!

I am quite new to Python and I have maybe simple (or maybe not)
question.

Is it possible to restart generator when it is exhausted?
For example:
>>> a = ['a', 'b', 'c']
>>> g = (i for i in a)
>>> g.next()
'a'
>>> g.next()
'b'
>>> g.next()
'c'
>>> g.next()
Traceback (most recent call last):
  File "", line 1, in 
g.next()
StopIteration
>>>
What should I do to get the initial state of g? So if I do again g.next
() I receive 'a'.

If it is not possible what are common techniques to use iterator or
generator objects that allow restarting when it is needed?

With regards,
Max

(sorry if my English isn't very proper)
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Re: Restart generator when it is exhausted.

[Lacrima]

On Apr 28, 1:04 pm, Chris Rebert  wrote:
> On Tue, Apr 28, 2009 at 2:54 AM, Lacrima  wrote:
> > Hello!
>
> > I am quite new to Python and I have maybe simple (or maybe not)
> > question.
>
> > Is it possible to restart generator when it is exhausted?
>
> No. You have to make a new instance of the generator.
>
> > What should I do to get the initial state of g? So if I do again g.next
> > () I receive 'a'.
>
> g = (i for i in a) #that is, make a fresh generator instance
>
> > If it is not possible what are common techniques to use iterator or
> > generator objects that allow restarting when it is needed?
>
> There's itertools.cycle() 
> --http://docs.python.org/library/itertools.html#itertools.cycle
>
> Cheers,
> Chris
> --http://blog.rebertia.com

Chris, thanks a lot for the help!
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Efficient bits manipulation in Python

[Li Wang]

Hi:

I have a bit-code :'1011011', how can I reverse it to '1101101'?

Another question is I know how to transform the string '110' into
integer 6, does anyone know how to transform integer 6 to a string
'110'?

Thank you very much:)


-- 
Li
--
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and you may find one day
you have less than you think
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RE: screen scraping with Python?

[Meenakshi, Arun Kumar]

David,

Thanks a ton for your swift reply. I will be more happy, if
you could direct me with right API with which I can walk further.

 

Regards,

Arun

FoneNet : 390-13359

Mobile: 9884471702

 

-Original Message-
From: David Lyon [mailto:david.l...@preisshare.net] 
Sent: Tuesday, April 28, 2009 4:52 PM
To: Meenakshi, Arun Kumar
Cc: python-list@python.org
Subject: Re: screen scraping with Python?

 

 

 

On Mon, 27 Apr 2009 12:28:31 +0530, "Meenakshi, Arun Kumar"

 wrote:

> Hi Friends,

> 

> Please let me know whether VT100 (Screen scrapping)

> emulation is possible or not. If screen scrapping / VT100 emulation is

> possible, please let me know how to do it. I will be happier, if you
can

> provide me steps and sample codes. I am a beginner in python. So
kindly

> help me by letting me know about the possibilities. EXPECTING THE
REPLY

> MAIL Thanks

 

Of course...

 

VT-100 terminals were usually rs-232 devices connected at 9600 baud

 

If you can write some python code talking to the serial port, you can

easily read the data from the port... render it... and do whatever you

need...

 

If you are doing it over a network then you are using a terminal
emulator.

 

Many of the top name termninal emulators provide a programming api.

 

If not.. go open source

 

There are just many.. many different ways these days... depending on

what platform and which terminal emulator you are using...

 

David

 


This email and any attachments are confidential and may also be privileged.  If 
you are not the addressee, do not disclose, copy, circulate or in any other way 
use or rely on the information contained in this email or any attachments.  If 
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attachments and may monitor email traffic.

 

Standard Chartered PLC is incorporated in England with limited liability under 
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London, EC2V 7SB.

 

Standard Chartered Bank ("SCB") is incorporated in England with limited 
liability by Royal Charter 1853, under reference ZC18.  The Principal Office of 
SCB is situated in England at 1 Aldermanbury Square, London EC2V 7SB. In the 
United Kingdom, SCB is authorised and regulated by the Financial Services 
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RE: screen scraping with Python?

[Jean-Paul Calderone]

On Tue, 28 Apr 2009 16:57:18 +0530, "Meenakshi, Arun Kumar" 
 wrote:

David,

   Thanks a ton for your swift reply. I will be more happy, if
you could direct me with right API with which I can walk further.



Twisted includes a vt102 API along with an in-memory emulator implementing
many (but not all) of the features of the terminal.  You can find the API
documentation online:

 http://twistedmatrix.com/documents/current/api/twisted.conch.insults.html

Jean-Paul
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Re: Efficient bits manipulation in Python

[Maxim Khitrov]

On Tue, Apr 28, 2009 at 7:26 AM, Li Wang  wrote:
> Hi:
>
> I have a bit-code :'1011011', how can I reverse it to '1101101'?
>
> Another question is I know how to transform the string '110' into
> integer 6, does anyone know how to transform integer 6 to a string
> '110'?
>
> Thank you very much:)

Assuming that you are using 2.6:

a = 0b1011011
print bin(a)[:1:-1]

a = 6
print bin(a)[2:]

- Max
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Re: Web based application development using python

[Rahul]

On Apr 28, 1:02 pm, Marco Mariani  wrote:
> Rahul wrote:
> > 1) Do you have any idea about web based support (like mod_python)
> > provided by python.org (official web site)
>
> > Details: - As we know mod_python is used for embeding python code into
> > apache server.
> > so, i want to know whether mod_python is officially supported by
> > python.org or if there is
> > other such framework for embeding python on web server
>
> Forget about mod_python, everything else is better.
>
> This list (the first result upon googling for "python web frameworks")
> is actually up to date, and a good start.
>
> http://wiki.python.org/moin/WebFrameworks
>
> Just don't ask which one is best for everything, or which one is The
> Official Standard Way Of Doing Things.

but i want to know which is the official standard recommended by
python.
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Unknown Visual C++ error

[Stef Mientki]

hello,

Anyone knows what this error message means ?

Python 2.5.2



thanks,
Stef


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Re: Using ascii numbers in regular expression

[jorma kala]

Thanks very much for your reply.
What I mean is that I would like to use the ascii number in a regular
expression pattern.
For instance, if I want to substitute the occurrences of character 'a' for
the character 'b' in a string, instead of doing this:

re.subn('a','b','')

I'd like to specify the ascii number of a (which is 97)
I tried converting 97 to hexadecimal (with hex()) and tried this

re.subn(''\0x61,'b','')

but it doesnt work.
I need this because I'm working on non printable characters.

Thanks a lot



On Tue, Apr 28, 2009 at 12:45 PM, Chris Rebert  wrote:

>  On Tue, Apr 28, 2009 at 4:05 AM, jorma kala  wrote:
> > Hi,
> >
> > How can I use the ascii number of a character in a regular expression
> > (module re) instead of the character itself?
> > Thanks very much
>
> I refer you to the chr() and ord() built-in functions, which can
> certainly be used to solve your problem, though they are not
> regex-specific in application.
> http://docs.python.org/library/functions.html
>
> Cheers,
> Chris
> --
> http://blog.rebertia.com
>
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Re: Efficient bits manipulation in Python

[Li Wang]

>> I have a bit-code :'1011011', how can I reverse it to '1101101'?
>>
>> Another question is I know how to transform the string '110' into
>> integer 6, does anyone know how to transform integer 6 to a string
>> '110'?
>>
>> Thank you very much:)
>
> Assuming that you are using 2.6:
>
> a = 0b1011011
> print bin(a)[:1:-1]
>
> a = 6
> print bin(a)[2:]

Thank you very much, that works:).

>
> - Max
>



-- 
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--
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and you may find one day
you have less than you think
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Re: Web based application development using python

[Tim Hoffman]

On Apr 28, 7:50 pm, Rahul  wrote:
> On Apr 28, 1:02 pm, Marco Mariani  wrote:
>
>
>
> > Rahul wrote:
> > > 1) Do you have any idea about web based support (like mod_python)
> > > provided by python.org (official web site)
>
> > > Details: - As we know mod_python is used for embeding python code into
> > > apache server.
> > > so, i want to know whether mod_python is officially supported by
> > > python.org or if there is
> > > other such framework for embeding python on web server
>
> > Forget about mod_python, everything else is better.
>
> > This list (the first result upon googling for "python web frameworks")
> > is actually up to date, and a good start.
>
> >http://wiki.python.org/moin/WebFrameworks
>
> > Just don't ask which one is best for everything, or which one is The
> > Official Standard Way Of Doing Things.
>
> but i want to know which is the official standard recommended by
> python.

But there isn't

There are a number of frameworks out there each with there own set of
strengths and weaknesses,  you shoul dbe
looking at each ones vibrancy (community), suitablility for your
application, etc...

T

T
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Re: python segfaulting, MemoryError (PyQt)

[Diez B. Roggisch]

>> As the documentation of pyqt clearly states, connecting signals doesn't
>> increment the refcount on a passed slot, thus
>>   you need to keep a reference to your slots around.
> 
> But it does increase the refcount for lambda slots.

Has that changed? It has been a while, but I've been bitten by this before,
so I was pretty sure about my answer.

Diez
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Re: Why bool( object )?

[Colin J. Williams]

Lie Ryan wrote:

Aaron Brady wrote:

What is the rationale for considering all instances true of a user-
defined type?  


User-defined objects (or type) can override .__len__() [usually 
container types] or .__nonzero__() to make bool() returns False.



Is it strictly a practical stipulation, or is there
something conceptually true about objects?


Objects are true unless they define themself as false. The practical 
implication is we can do this:


def foo(args = None):
if args:
...

In python all objects are true except: None, False, 0/0L/0.0/0j, empty 
sequence or container, and on objects that defines .__len__() or 
..__nonzero__() that returns 0 or False.



'''
object.__bool__(self)
If a class defines neither __len__() nor __bool__(), all its instances
are considered true.
'''

This makes it so all objects except False, None, 0, and empty
containers are true by default.  I am not convinced that 'if ' should have any meaning; it should probably throw an
exception.  Is it part of Python's look and feel or its mentality?  Is
it part of the Zen?  Certainly other ideal types can't be cast from
generic objects, so why booleans?  Is it an ineffable component of the
author's vision for the language?  I think that giving arbitrary
syntactic constructs meaning is just space-filler.  It's worse than
syntactic sugar, it's semantic sugar.  Why not assign meanings willy-
nilly to other random juxtapositions of tokens?


It's part of the design decision. In almost all cases (in any language), 
a so-called "Design Decision" is rather random and prone to subjective 
judgment, just as the decision to make bool(int) returns False only on 
0, -1, or for all negative values; whether to make bool(100) and 
exception or True; or round() rounds down or up or even-odd; or the use 
of brackets vs. indentation; or whether to treat empty list as True or 
False.


I'm puzzled by the last sentence:

*** Python 2.6.2 (r262:71605, Apr 14 
2009, 22:40:02) [MSC v.1500 32 bit 
(Intel)] on win32. ***

bool(0)

False

bool(-1)

True

bool(-100)

True




Colin W.
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Connecting/talking to OpenOffice Base files

[deostroll]

Hi,

I was wondering if the python interpretor can talk to files with
extension *.odb (OpenOffice Base files). They are like flat database
files, similar to Microsoft Access files. I want to store data into
them as well as extract data out of them.

--deostroll
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Re: Using ascii numbers in regular expression

[Chris Rebert]

On Tue, Apr 28, 2009 at 4:58 AM, jorma kala  wrote:
> Thanks very much for your reply.
> What I mean is that I would like to use the ascii number in a regular
> expression pattern.
> For instance, if I want to substitute the occurrences of character 'a' for
> the character 'b' in a string, instead of doing this:
>
> re.subn('a','b','')
>
> I'd like to specify the ascii number of a (which is 97)
> I tried converting 97 to hexadecimal (with hex()) and tried this

You should go the more direct route, as my function recommendation implied:

assert chr(97) == "a"
re.subn(chr(97),'b','')

Cheers,
Chris
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Re: Using ascii numbers in regular expression

[Chris Rebert]

On Tue, Apr 28, 2009 at 4:05 AM, jorma kala  wrote:
> Hi,
>
> How can I use the ascii number of a character in a regular expression
> (module re) instead of the character itself?
> Thanks very much

I refer you to the chr() and ord() built-in functions, which can
certainly be used to solve your problem, though they are not
regex-specific in application.
http://docs.python.org/library/functions.html

Cheers,
Chris
-- 
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Re: Why bool( object )?

[Lawrence D'Oliveiro]

In message <54cb7f8a-
fef4-4bf8-8054-16dc9b5c8...@d2g2000pra.googlegroups.com>, Aaron Brady wrote:

> What is the rationale for considering all instances true of a user-
> defined type?

It's a stupid idea, and there seem to be instances of users tripping over it 
here in comp.lang.python every week.

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Re: The whole story

[andrew cooke]

Paul Hemans wrote:
> Hi Andrew,
> The reason I am using mapped objects is that I need to abstract from the
> database implementation allowing the replication to target a number of
> different platforms. This will definitely slow things down.

have you looked at sqlalchemy's generic sql support?  you can construct
sql "statements" using python classes/functions called "select", "update"
etc and sqlalchemy automatically makes things work with different database
implementations.  it's not perfect, but i have the same code working with
mysql and oracle, which covers quite a range :o)

>> process a whole pile in memory and then (perhaps every 10,000 - when
>> your
>> memory is about to run out and start paging) flush the session.
> Under windows how can I tell when memory is about to run out? I guess
> there
> is no cross-platform solution to this.

i don't know, sorry.

> Writing external files has all come about from a post titled "Memory
> problems (garbage collection) by Carbon Man" which I never got a
> resolution
> to.
> I was trying to execute gc.collect() when a process was complete because I
> was having huge problems with memory (though the problem still remains).
> If
> I stop at "import schema" There are 2524104 objects processed by
> gc.collect()

you shouldn't need to call gc.collect().

when you write everything out to the database, if you have no other
references to the objects, python will clean them up automatically. 
calling gc.collect() won't make any difference - python's gc already works
just fine.

if your memory use isn't going down then either (1) you are not writing
out/flushing correctly (if you want i can check my code later today and
tell you exactly what i do) or you are keeping references to your objects
elsewhere (eg in a dictionary in the code you use to construct them).

andrew


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Re: Restart generator when it is exhausted.

[Duncan Booth]

Lacrima  wrote:

> If it is not possible what are common techniques to use iterator or
> generator objects that allow restarting when it is needed?

The usual thing if you want to use the generator's output more than once  
would be to convert the generator to a list, then you can iterate over it 
as often as you want.

>>> a = ['a', 'b', 'c']
>>> g = (i for i in a)
>>> restartable = list(g)

If you want the output of the generator to potentially change each time you 
iterate then you need to create a new generator.

-- 
Duncan Booth http://kupuguy.blogspot.com
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Re: Why bool( object )?

[Andre Engels]

On Tue, Apr 28, 2009 at 2:22 PM, Colin J. Williams  wrote:
> Lie Ryan wrote:
>>
>> Aaron Brady wrote:
>>>
>>> What is the rationale for considering all instances true of a user-
>>> defined type?
>>
>> User-defined objects (or type) can override .__len__() [usually container
>> types] or .__nonzero__() to make bool() returns False.
>>
>>> Is it strictly a practical stipulation, or is there
>>> something conceptually true about objects?
>>
>> Objects are true unless they define themself as false. The practical
>> implication is we can do this:
>>
>> def foo(args = None):
>>    if args:
>>        ...
>>
>> In python all objects are true except: None, False, 0/0L/0.0/0j, empty
>> sequence or container, and on objects that defines .__len__() or
>> ..__nonzero__() that returns 0 or False.
>>
>>> '''
>>> object.__bool__(self)
>>> If a class defines neither __len__() nor __bool__(), all its instances
>>> are considered true.
>>> '''
>>>
>>> This makes it so all objects except False, None, 0, and empty
>>> containers are true by default.  I am not convinced that 'if >> generic object>' should have any meaning; it should probably throw an
>>> exception.  Is it part of Python's look and feel or its mentality?  Is
>>> it part of the Zen?  Certainly other ideal types can't be cast from
>>> generic objects, so why booleans?  Is it an ineffable component of the
>>> author's vision for the language?  I think that giving arbitrary
>>> syntactic constructs meaning is just space-filler.  It's worse than
>>> syntactic sugar, it's semantic sugar.  Why not assign meanings willy-
>>> nilly to other random juxtapositions of tokens?
>>
>> It's part of the design decision. In almost all cases (in any language), a
>> so-called "Design Decision" is rather random and prone to subjective
>> judgment, just as the decision to make bool(int) returns False only on 0,
>> -1, or for all negative values; whether to make bool(100) and exception or
>> True; or round() rounds down or up or even-odd; or the use of brackets vs.
>> indentation; or whether to treat empty list as True or False.
>
> I'm puzzled by the last sentence:
>
> *** Python 2.6.2 (r262:71605, Apr 14 2009, 22:40:02) [MSC v.1500 32 bit
> (Intel)] on win32. ***

 bool(0)
>
> False

 bool(-1)
>
> True

 bool(-100)
>
> True

>
> Colin W.
> --
> http://mail.python.org/mailman/listinfo/python-list
>

bool has been defined thus in Python:

False are:
* False
* None
* empty containers, lists etc.
* The number zero

Everything else is true.

-100 is not equal to zero, so its boolean value is True.



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Re: Connecting/talking to OpenOffice Base files

[Krishnakant]

hi,
On Tue, 2009-04-28 at 05:24 -0700, deostroll wrote:
> Hi,
> 
> I was wondering if the python interpretor can talk to files with
> extension *.odb (OpenOffice Base files). They are like flat database
> files, similar to Microsoft Access files. I want to store data into
> them as well as extract data out of them.
> 
This is done either  using ooolib if you want to do some simple read and
write tasks or then use odfpy which is a complete library.

I had asked the same question a few months back and come from the same
path you are coming.

But odfpy was initially difficult for me and would take a while to
understand.
It is a kind of wrapper around the xml structure of an odf document.

happy hacking.
Krishnakant.

> --deostroll
> --
> http://mail.python.org/mailman/listinfo/python-list

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[ANN] pyOpenSSL 0.9

[Jean-Paul Calderone]

I'm happy to announce the release of pyOpenSSL 0.9. This release includes
several new features and a very important bug fix:

 * APIs have been introduced to get and set the version of an X509 request
 * Contexts now support loading CA certificates for verification from a
   specified directory or from the platform's default certificate store
 * DTLS-related constants, OP_NO_QUERY_MTU, OP_COOKIE_EXCHANGE, and
   OP_NO_TICKET are now exposed
 * X509Extension now has the `get_short_name´ method for retrieving the
   short form of the extension type
 * It is now possible to create extensions which use any of the three
   possible OpenSSL implementation approaches
 * FILETYPE_TEXT can be used to dump keys, certificate, and CSRs in text
   format
 * Various compiler warnings have been fixed
 * A bug triggered by almost all uses of pyOpenSSL from multiple threads
   and leading to a crash has been fixed

Many thanks to numerous people who contributed patches to this release.

You can find pyOpenSSL 0.9 in the downloads area of the SourceForge project
page:

   https://sourceforge.net/project/showfiles.php?group_id=31249

Please use Launchpad to file any bug reports:

   https://bugs.launchpad.net/pyopenssl

Jean-Paul Calderone
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Re: Is there a maximum size to a Python program?

[Paul Boddie]

On 27 Apr, 05:01, "Carbon Man"  wrote:
> I have a program that is generated from a generic process. It's job is to
> check to see whether records (replicated from another system) exist in a
> local table, and if it doesn't, to add them. I have 1 of these programs for
> every table in the database.

Some people have discussed whether you need one or many programs. In
practice, you're going to need to execute many "tasks" to process all
your tables, and potentially this could mean generating many SQL
statements, as I will describe below.

[...]

> I am thinking that dynamically generating the programs to run might not be
> such a good idea. It would be a shame to drop it because the system needs to
> be generic and it runs from an XML file so the resulting code could be
> pretty complex, and I am new to Python. The program did generate a pyc so it
> was able to compile.
> Thoughts anyone?

This problem sounds as if it could be solved adequately using only the
database system, although I accept that sometimes some logic or
additional processing could be done in Python. If I were to receive
updates from a system, presumably as files, I'd want to bulk copy them
into the database and then perform the necessary inserts using SQL. If
the raw updates were not directly compatible with the database,
perhaps because data representations might differ, then I would want
to process them before doing the bulk copy.

In other words, the workflow for a single table would look like this:

 1. Obtain update files.
 2. Process files in order to make the data compatible with the
database.
 3. Create temporary tables for the updates in the database.
 4. Bulk copy the files into the temporary tables (using COPY or LOAD
DATA commands).
 5. Do the necessary inserts (where you have to either use the non-
standard
INSERT OR UPDATE or an INSERT involving a join between existing
and temporary tables).
 6. Drop the temporary tables (if not done automatically).

Now, it's almost certain that the details of the above workflow would
vary from table to table and from update to update. Even in the case
where you don't have to process the files, you still need to copy the
files into the database and to work with a different table each time.
This is where generating "something" for each table is unavoidable,
and one solution might be to have a generic template and to substitute
the table name and update filename into that template as you process
each table and its associated data. Whether you actually generate an
SQL command file for each table, or whether you have a program issue
the commands directly, is a matter of preference.

Anyway, from what you've described, that's how I would approach this
problem. Certainly, it's a lot more straightforward than dealing with
object-relational abstractions in programs generated by other
programs.

Paul
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Re: Web framework for embedded system

[bobicanprogram]

On Apr 28, 3:43 am, Thomas Heller  wrote:
> I'm looking for a lightweight web-framework for an embedded system.
> The system is running a realtime linux-variant on a 200 MHz ARM
> processor, Python reports a performance of around 500 pystones.
>
> The web application will not be too fancy, no databases involved
> for example, but it will need to control some simple peripherals
> (some parallel in/out, some dacs) attached to the system.
>
> It should provide a user interface showing the current state and
> allowing to manipulate it via a browser, and I will probably need
> to support some rpc as well.
>
> Does this sound sensible at all? Any suggestions?
>
> Thomas


You should definitely check out the SIMPL toolkit (http://
www.icanprogram.com/simpl).  We have used this ultra lightweight
toolkit in several embedded Linux projects.   It will allow you to
seamlessly connect your Python bits with bits more appropriately
written in other languages like C.

There is a "hello world" level tutorial on the Python-SIMPL
capabilities (which includes a web CGI interface) at:

http://www.icanprogram.com/06py/main.html

If you have any questions about our SIMPL experiences don't hesitate
to ask.

bob
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Re: python segfaulting, MemoryError (PyQt)

[Denis L]

"Phil Thompson"  wrote in message 
news:mailman.4664.1240907352.11746.python-l...@python.org...
> On Tue, 28 Apr 2009 03:53:34 +0200, "Denis L"  wrote:
>> Hello,
>>
>> I'm experiencing odd errors on both windows and linux with the following
>> code:
>>
>> import sys
>> from PyQt4.QtCore import *
>> from PyQt4.QtGui import *
>>
>> class Options(QDialog):
>> def __init__(self, values):
>> QDialog.__init__(self)
>>
>> self.values = values
>>
>> fooEdit = QLineEdit(values['foo'])
>> self.connect(fooEdit, SIGNAL('textChanged(QString)'),
>>  lambda value: self.optionChanged('foo', value))
>>
>> barEdit = QLineEdit(values['bar'])
>> self.connect(barEdit, SIGNAL('textChanged(QString)'),
>>  lambda value: self.optionChanged('bar', value))
>>
>> layout = QVBoxLayout()
>> layout.addWidget(fooEdit)
>> layout.addWidget(barEdit)
>>
>> self.setLayout(layout)
>>
>> def optionChanged(self, option, value):
>> self.values[option] = value
>> print self.values
>>
>> def main(args):
>> app = QApplication(args)
>> values = dict(foo='', bar='')
>> dialog = Options(values)
>> dialog.show()
>> app.exec_()
>>
>> if __name__ == '__main__':
>> main(sys.argv)
>>
>>
>> If I type a character in fooEdit, another character in barEdit, and then
>> delete the character from barEdit I get an unhandled win32 exception
>> occured
>> in python.exe on windows and segfault on linux.
>>
>> If I type a character in fooEdit, delete it, and then type a character in
>
>> barEdit I get:
>>
>> {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
>> {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
>> {'foo': Traceback (most recent call last):
>>   File "L:\home\dev\python\test.py", line 17, in 
>> lambda value: self.optionChanged('bar', value))
>>   File "L:\home\dev\python\test.py", line 27, in optionChanged
>> print self.values
>> MemoryError
>>
>> I'm using Python 2.5.4 and PyQt 4.4.3-1
>>
>> Thanks in advance for any help.
>
> Works fine for me with current versions.
>
> Phil

I have noticed that if I do "self.values[option] = QString(value)"
instead of "self.values[option] = value" in optionChanged I don't get any 
errors.

Is it perhaps not safe to keep the reference to the lambda QString argument? 


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Getting the "dir" from the other ancestor ?

[Stef Mientki]

hello,

I have a class, derived from some user defined class 
(User_Defined_Ancestor) and some basic class (Basic_Ancestor).


One of the major tasks of the Basic_Ancestor,
is to hide all kinds of implementation details for the user,
so the user can concentrate on the functional design.

One of things I need to know are the methods and attributes of the 
Basic_Ancestor.

Both classes are dynamic, i.e. attributes are added during run time.

class Master ( User_Defined_Ancestor, Basic_Ancestor ) :
   def __init__ ( self, *args, **kwargs ) :
   Basic_Ancestor.__init__ ( self, *args, **kwargs )
   .

class Basic_Ancestor ( object ) :
   def __init__ ( self,  ) :
   self.other = dir ( User_Defined_Ancestor )

   def Get_Attributes ( self ) :
   return dir ( self ) - dir ( self.other )


Now the problem is, I don't know "User_Defined_Ancestor" in Basic_Ancestor.
I can't pass it through the parameter list, because I use "*args, **kwargs"
I possibly could use some global variable, but that's not my preference.

Any other suggestions ?

thanks,
Stef Mientki


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Re: Getting the "dir" from the other ancestor ?

[tuxagb]

On 28 Apr, 15:01, Stef Mientki  wrote:
> hello,
>
> I have a class, derived from some user defined class
> (User_Defined_Ancestor) and some basic class (Basic_Ancestor).
>
> One of the major tasks of the Basic_Ancestor,
> is to hide all kinds of implementation details for the user,
> so the user can concentrate on the functional design.
>
> One of things I need to know are the methods and attributes of the
> Basic_Ancestor.
> Both classes are dynamic, i.e. attributes are added during run time.
>
> class Master ( User_Defined_Ancestor, Basic_Ancestor ) :
>     def __init__ ( self, *args, **kwargs ) :
>         Basic_Ancestor.__init__ ( self, *args, **kwargs )
>         .
>
> class Basic_Ancestor ( object ) :
>     def __init__ ( self,  ) :
>         self.other = dir ( User_Defined_Ancestor )
>
>     def Get_Attributes ( self ) :
>         return dir ( self ) - dir ( self.other )
>
> Now the problem is, I don't know "User_Defined_Ancestor" in Basic_Ancestor.
> I can't pass it through the parameter list, because I use "*args, **kwargs"
> I possibly could use some global variable, but that's not my preference.
>
> Any other suggestions ?
>
> thanks,
> Stef Mientki

In anytime, if you do dir() in a class B, that extends a class A, you
have all fields of A also.

Example:

>>> class A:
...def a(self):
...return 0
>>> class B(A):
...def b(self):
...return 5
>>> dir(A)
[., 'a']
>>> dir(B)
[.., 'a', 'b']

Hi.
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Re: mailbox.mbox.add() sets access time as well as modification time

[Grant Edwards]

On 2009-04-27, Lawrence D'Oliveiro  wrote:
> In message , Aahz wrote:
>
>> In article ,
>> Lawrence D'Oliveiro   wrote:
>>>
>>>It's only in the proprietary-software world that we need to worry about
>>>backward compatibility with old, obsolete software that the vendors
>>>cannot or will not fix. In the Free Software world, we fix the software
>>>to bring it up to date.
>> 
>> Are you volunteering to maintain trn3.6?
>
> Either there are enough people using it to care about it, in which case 
> somebody in the community will fix it, it or there are not, in which case
> it's not worth bothering with.

Except _it's_not_broken_.  It follows the established set of
rules for manipulating mbox mailboxes. It follows the set of
rules that all other mbox MUAs and MTAs use.  Python's library
is not following the rules, and your response is that the rest
of the world should change?

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   pet LEISURE SUIT!!
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Re: mailbox.mbox.add() sets access time as well as modification time

[Grant Edwards]

On 2009-04-27, Lawrence D'Oliveiro  wrote:

>> Who's "we"?  Are you volunteering to fix all of the MUAs and
>> MTAs out there that have mbox code in them that do follow the
>> rules to make them compatible with _one_ broken library
>> module?
>
> All the MUAs and MTAs I'm aware of that are worth bothering
> about have the option to support maildir format these days.

That sure seems like a rather unhelpful response when somebody
finds a bug in the standard library:

 1) Don't use that module.
 
 2) Change the rest of the world to work around Python's bug.

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Re: python segfaulting, MemoryError (PyQt)

[Phil Thompson]

On Tue, 28 Apr 2009 14:54:41 +0200, "Denis L"  wrote:
> "Phil Thompson"  wrote in message 
> news:mailman.4664.1240907352.11746.python-l...@python.org...
>> On Tue, 28 Apr 2009 03:53:34 +0200, "Denis L"  wrote:
>>> Hello,
>>>
>>> I'm experiencing odd errors on both windows and linux with the
following
>>> code:
>>>
>>> import sys
>>> from PyQt4.QtCore import *
>>> from PyQt4.QtGui import *
>>>
>>> class Options(QDialog):
>>> def __init__(self, values):
>>> QDialog.__init__(self)
>>>
>>> self.values = values
>>>
>>> fooEdit = QLineEdit(values['foo'])
>>> self.connect(fooEdit, SIGNAL('textChanged(QString)'),
>>>  lambda value: self.optionChanged('foo', value))
>>>
>>> barEdit = QLineEdit(values['bar'])
>>> self.connect(barEdit, SIGNAL('textChanged(QString)'),
>>>  lambda value: self.optionChanged('bar', value))
>>>
>>> layout = QVBoxLayout()
>>> layout.addWidget(fooEdit)
>>> layout.addWidget(barEdit)
>>>
>>> self.setLayout(layout)
>>>
>>> def optionChanged(self, option, value):
>>> self.values[option] = value
>>> print self.values
>>>
>>> def main(args):
>>> app = QApplication(args)
>>> values = dict(foo='', bar='')
>>> dialog = Options(values)
>>> dialog.show()
>>> app.exec_()
>>>
>>> if __name__ == '__main__':
>>> main(sys.argv)
>>>
>>>
>>> If I type a character in fooEdit, another character in barEdit, and
then
>>> delete the character from barEdit I get an unhandled win32 exception
>>> occured
>>> in python.exe on windows and segfault on linux.
>>>
>>> If I type a character in fooEdit, delete it, and then type a character
>>> in
>>
>>> barEdit I get:
>>>
>>> {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
>>> {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
>>> {'foo': Traceback (most recent call last):
>>>   File "L:\home\dev\python\test.py", line 17, in 
>>> lambda value: self.optionChanged('bar', value))
>>>   File "L:\home\dev\python\test.py", line 27, in optionChanged
>>> print self.values
>>> MemoryError
>>>
>>> I'm using Python 2.5.4 and PyQt 4.4.3-1
>>>
>>> Thanks in advance for any help.
>>
>> Works fine for me with current versions.
>>
>> Phil
> 
> I have noticed that if I do "self.values[option] = QString(value)"
> instead of "self.values[option] = value" in optionChanged I don't get any

> errors.
> 
> Is it perhaps not safe to keep the reference to the lambda QString
> argument? 

It shouldn't make any difference.

Phil
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Re: Using ascii numbers in regular expression

[MRAB]

jorma kala wrote:

Thanks very much for your reply.
What I mean is that I would like to use the ascii number in a regular 
expression pattern.
For instance, if I want to substitute the occurrences of character 'a' 
for the character 'b' in a string, instead of doing this:
 
re.subn('a','b','')
 
I'd like to specify the ascii number of a (which is 97)

I tried converting 97 to hexadecimal (with hex()) and tried this
 
re.subn(''\0x61,'b','')
 
but it doesnt work.

I need this because I'm working on non printable characters.
 

[snip]
You're almost there:

re.subn('\x61','b','')

or better yet:

re.subn(r'\x61','b','')
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Re: python segfaulting, MemoryError (PyQt)

[Diez B. Roggisch]

Phil Thompson wrote:

> On Tue, 28 Apr 2009 11:18:31 +0200, "Diez B. Roggisch"
> 
> wrote:
 As the documentation of pyqt clearly states, connecting signals doesn't
 increment the refcount on a passed slot, thus
   you need to keep a reference to your slots around.
>>> 
>>> But it does increase the refcount for lambda slots.
>> 
>> Has that changed? It has been a while, but I've been bitten by this
> before,
>> so I was pretty sure about my answer.
> 
> Support for lambda slots was add in PyQt v4.1.1 (released December 2006).

Unfortunately after I had the chance to play with PyQt for the last time.
Thanks for clarifying!

Diez
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Query related to matplotlib

[srinivasan srinivas]

I would like to draw a chart which takes 'dates' in x axes and some values in y 
axes.  
I would like to draw a simple chart using matplotlib. Can someone tell me which 
submodule i could use for this purpose? The module has to support in the way 
that i can draw more than one set can be passed to Y axes. So it will generate 
more than one line.

Thanks,
Srini



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Edition http://downloads.yahoo.com/in/firefox/
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Re: Help AIX 5.3 build on Python-3.1a2

[Jeroen Ruigrok van der Werven]

-On [20090427 20:31], prueba...@latinmail.com (prueba...@latinmail.com) wrote:
>./Modules/ld_so_aix xlc_r -q64 -bI:Modules/python.exp build/
>temp.aix-5.3-3.1//ptst/Python-3.1a2/Modules/_tkinter.o build/
>temp.aix-5.3-3.1//ptst/Python-3.1a2/Modules/tkappinit.o -L/usr/X11R6/
>lib64 -L/usr/X11R6/lib -L/usr/local/lib -ltk8.3 -ltcl8.3 -lX11 -o
>build/lib.aix-5.3-3.1/_tkinter.so
>ld: 0706-006 Cannot find or open library file: -l tk8.3
>ld:open(): A file or directory in the path name does not
>exist.

Well, do you have TK installed? It seems so, but are the paths passed to the
compiler/linker correct (-L) for locating libtk8.3.so?

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Re: Web based application development using python

[Rahul]

On Apr 28, 5:07 pm, Tim Hoffman  wrote:
> On Apr 28, 7:50 pm, Rahul  wrote:
>
>
>
> > On Apr 28, 1:02 pm, Marco Mariani  wrote:
>
> > > Rahul wrote:
> > > > 1) Do you have any idea about web based support (like mod_python)
> > > > provided by python.org (official web site)
>
> > > > Details: - As we know mod_python is used for embeding python code into
> > > > apache server.
> > > > so, i want to know whether mod_python is officially supported by
> > > > python.org or if there is
> > > > other such framework for embeding python on web server
>
> > > Forget about mod_python, everything else is better.
>
> > > This list (the first result upon googling for "python web frameworks")
> > > is actually up to date, and a good start.
>
> > >http://wiki.python.org/moin/WebFrameworks
>
> > > Just don't ask which one is best for everything, or which one is The
> > > Official Standard Way Of Doing Things.
>
> > but i want to know which is the official standard recommended by
> > python.
>
> But there isn't
>
> There are a number of frameworks out there each with there own set of
> strengths and weaknesses,  you shoul dbe
> looking at each ones vibrancy (community), suitablility for your
> application, etc...
>
> T
>
> T

Thanks tim
This information was really of help to me
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Re: Web framework for embedded system

[Suraj Barkale]

Thomas Heller  python.net> writes:
> 
> I'm looking for a lightweight web-framework for an embedded system.
> The system is running a realtime linux-variant on a 200 MHz ARM
> processor, Python reports a performance of around 500 pystones.

You can start with webpy (http://webpy.org/) and build up from there.

> 
> The web application will not be too fancy, no databases involved
> for example, but it will need to control some simple peripherals
> (some parallel in/out, some dacs) attached to the system.
> 
> It should provide a user interface showing the current state and
> allowing to manipulate it via a browser, and I will probably need
> to support some rpc as well.
> 
> Does this sound sensible at all? Any suggestions?

I don't know how Python will affect the real-time tasks your system is
performing. You may want to look at a web framework in C (e.g.
http://www.koanlogic.com/klone/index.html).
Regards,
Suraj


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Re: Re: sorted() erraticly fails to sort string numbers

[John Posner]

uuid wrote:
I am at the same time impressed with the concise answer and 
disheartened by my inability to see this myself.

My heartfelt thanks!
Don't be disheartened! Many people -- myself included, absolutely! -- 
occasionally let a blind spot show in their messages to this list. BTW:


   container[:] = sorted(container, key=getkey)

... is equivalent to:

   container.sort(key=getkey)

(unless I'm showing *my* blind spot here)

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How to locate the bit in bits string?

[Li Wang]

Hi:

If I use an integer to represent bits:
e.g. 99 represents '1100011'

How can I locate, say the second bit of 99(i.e. '1')?

Although bin(99)[4] could be used to locate it, this transform cost
too much memory (99 only needs 2Bytes, while string '1100011' needs
7Bytes).

Anyone knows how to locate  the second bit without using bin() function?

Thank you very much:D

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--
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and you may find one day
you have less than you think
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Re: sorted() erraticly fails to sort string numbers

[uuid]

On 2009-04-28 16:18:43 +0200, John Posner  said:

Don't be disheartened! Many people -- myself included, absolutely! -- 
occasionally let a blind spot show in their messages to this list.


Thanks for the encouragement :)


BTW:

container[:] = sorted(container, key=getkey)

... is equivalent to:

container.sort(key=getkey)

(unless I'm showing *my* blind spot here)


I don't think etree element objects support the .sort method.
At least in lxml they don't 
(http://codespeak.net/lxml/api/elementtree.ElementTree.Element-class.html) 



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Re: Best way to evaluate boolean expressions from strings?

[Gustavo Narea]

Thank you very much,  Gabriela and Peter!

I'm going for Pyparsing. :)

  -- Gustavo.
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Re: How to locate the bit in bits string?

[Tim Chase]

Li Wang wrote:

Hi:

If I use an integer to represent bits:
e.g. 99 represents '1100011'

How can I locate, say the second bit of 99(i.e. '1')?

Although bin(99)[4] could be used to locate it, this transform cost
too much memory (99 only needs 2Bytes, while string '1100011' needs
7Bytes).

Anyone knows how to locate  the second bit without using bin() function?


You mean

  def get_bit(number, bit):
return (number >> bit) & 1

?

-tkc




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Third Party Modules

[Brock]

Hi Everyone,

I know this is most likely a basic question and you will roll your
eyes, but I am just starting out with Python (hobbyist) and I see many
tutorials on the web referring to the use of external modules.

However, when I locate them, they often come as a zipped folder with a
number of files.  How do I install them?  In addition, is there an
easy way to manage external modules? Some I see require additional
modules not included.

Where I am coming from is R, which has a point-and-click way of
getting packages not distributed with the version of the software, so
that is my point of reference.

Many thanks!

- Brock
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What do you think of ShowMeDo

[Astley Le Jasper]

Hi,

I've just stumbled over this (http://showmedo.com/) and being the very
visual person I am, it seems like it could be a good way to learn
about python. However, before I smack down $60, I wondered if anyone
had any opinions on it. My gut feel is that it could be pretty good.

ALJ
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Re: python segfaulting, MemoryError (PyQt)

[Denis L]

"Phil Thompson"  wrote in message 
news:mailman.4690.1240925876.11746.python-l...@python.org...
> On Tue, 28 Apr 2009 14:54:41 +0200, "Denis L"  wrote:
>> "Phil Thompson"  wrote in message
>> news:mailman.4664.1240907352.11746.python-l...@python.org...
>>> On Tue, 28 Apr 2009 03:53:34 +0200, "Denis L"  wrote:
 Hello,

 I'm experiencing odd errors on both windows and linux with the
> following
 code:

 import sys
 from PyQt4.QtCore import *
 from PyQt4.QtGui import *

 class Options(QDialog):
 def __init__(self, values):
 QDialog.__init__(self)

 self.values = values

 fooEdit = QLineEdit(values['foo'])
 self.connect(fooEdit, SIGNAL('textChanged(QString)'),
  lambda value: self.optionChanged('foo', value))

 barEdit = QLineEdit(values['bar'])
 self.connect(barEdit, SIGNAL('textChanged(QString)'),
  lambda value: self.optionChanged('bar', value))

 layout = QVBoxLayout()
 layout.addWidget(fooEdit)
 layout.addWidget(barEdit)

 self.setLayout(layout)

 def optionChanged(self, option, value):
 self.values[option] = value
 print self.values

 def main(args):
 app = QApplication(args)
 values = dict(foo='', bar='')
 dialog = Options(values)
 dialog.show()
 app.exec_()

 if __name__ == '__main__':
 main(sys.argv)


 If I type a character in fooEdit, another character in barEdit, and
> then
 delete the character from barEdit I get an unhandled win32 exception
 occured
 in python.exe on windows and segfault on linux.

 If I type a character in fooEdit, delete it, and then type a character
 in
>>>
 barEdit I get:

 {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
 {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
 {'foo': Traceback (most recent call last):
   File "L:\home\dev\python\test.py", line 17, in 
 lambda value: self.optionChanged('bar', value))
   File "L:\home\dev\python\test.py", line 27, in optionChanged
 print self.values
 MemoryError

 I'm using Python 2.5.4 and PyQt 4.4.3-1

 Thanks in advance for any help.
>>>
>>> Works fine for me with current versions.
>>>
>>> Phil
>>
>> I have noticed that if I do "self.values[option] = QString(value)"
>> instead of "self.values[option] = value" in optionChanged I don't get any
>
>> errors.
>>
>> Is it perhaps not safe to keep the reference to the lambda QString
>> argument?
>
> It shouldn't make any difference.
>
> Phil

Last idea, C++ declaration of textChanged signal is this:

void textChanged (const QString&text)

would self.values[option] = value store the reference to QString? And if so 
is that safe, to access that object after my slot returns?

As far as I can see C++ equivalent would be

QString* pointer = &text; then derferencing that pointer later in the code. 
I can see how this could cause problems.

Btw you are using PyQt 4.4.4 correct? What version of python? 


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Re: How to locate the bit in bits string?

[tuxagb]

On 28 Apr, 16:36, Li Wang  wrote:
> Hi:
>
> If I use an integer to represent bits:
> e.g. 99 represents '1100011'
>
> How can I locate, say the second bit of 99(i.e. '1')?
>
> Although bin(99)[4] could be used to locate it, this transform cost
> too much memory (99 only needs 2Bytes, while string '1100011' needs
> 7Bytes).
>
> Anyone knows how to locate  the second bit without using bin() function?
>
> Thank you very much:D
>
> --
> Li
> --
> Time is all we have
> and you may find one day
> you have less than you think

If we consider 8 bit, a solution may be the follow:

  >>> a = 99  # bin(a) = 0b1100011
  >>> 0b1101 & a
  97
  >>> 0b1110 & a
  99

as you view, you set the nth bit to 0, and view if the result is same
as 'a'. If is same
then the nth bit doesn't set. If you write the above code in a loop,
you can test which bit
you want.

Hi.
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Re: How to locate the bit in bits string?

[Li Wang]

2009/4/29 Tim Chase :
> Li Wang wrote:
>>
>> Hi:
>>
>> If I use an integer to represent bits:
>> e.g. 99 represents '1100011'
>>
>> How can I locate, say the second bit of 99(i.e. '1')?
>>
>> Although bin(99)[4] could be used to locate it, this transform cost
>> too much memory (99 only needs 2Bytes, while string '1100011' needs
>> 7Bytes).
>>
>> Anyone knows how to locate  the second bit without using bin() function?
>
> You mean
>
>  def get_bit(number, bit):
>return (number >> bit) & 1
>
> ?
>
Hummm, I have tried this method too, the problem is its time
complexity. If the length of my bits is n, then the time complexity is
O(n). When I tried to implement this in practice, it did consume a lot
of time.

So do you know how could I locate the bit in O(1) time? Transform it
into a string is a method, but takes too much space (when I try to
process a 2M file, it used more than 100M memory.).

Thank you very much.

> -tkc
>
>
>
>
>



-- 
Li
--
Time is all we have
and you may find one day
you have less than you think
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Re: Third Party Modules

[tuxagb]

On 28 Apr, 17:02, Brock  wrote:
> Hi Everyone,
>
> I know this is most likely a basic question and you will roll your
> eyes, but I am just starting out with Python (hobbyist) and I see many
> tutorials on the web referring to the use of external modules.
>
> However, when I locate them, they often come as a zipped folder with a
> number of files.  How do I install them?  In addition, is there an
> easy way to manage external modules? Some I see require additional
> modules not included.
>
> Where I am coming from is R, which has a point-and-click way of
> getting packages not distributed with the version of the software, so
> that is my point of reference.
>
> Many thanks!
>
> - Brock

If you are on Unix-like machine, unzip the archive in a some
directory, do cd into the new directory
and, from command line, do: python ./setup.py build (verify there is
the script setup.py), and then
python ./setup.py install (with root's permissions). On Win32 usually
there are an automatic  installer.

Hi.
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Re: python segfaulting, MemoryError (PyQt)

[Phil Thompson]

On Tue, 28 Apr 2009 17:10:51 +0200, "Denis L"  wrote:
> "Phil Thompson"  wrote in message 
> news:mailman.4690.1240925876.11746.python-l...@python.org...
>> On Tue, 28 Apr 2009 14:54:41 +0200, "Denis L"  wrote:
>>> "Phil Thompson"  wrote in message
>>> news:mailman.4664.1240907352.11746.python-l...@python.org...
 On Tue, 28 Apr 2009 03:53:34 +0200, "Denis L"  wrote:
> Hello,
>
> I'm experiencing odd errors on both windows and linux with the
>> following
> code:
>
> import sys
> from PyQt4.QtCore import *
> from PyQt4.QtGui import *
>
> class Options(QDialog):
> def __init__(self, values):
> QDialog.__init__(self)
>
> self.values = values
>
> fooEdit = QLineEdit(values['foo'])
> self.connect(fooEdit, SIGNAL('textChanged(QString)'),
>  lambda value: self.optionChanged('foo', value))
>
> barEdit = QLineEdit(values['bar'])
> self.connect(barEdit, SIGNAL('textChanged(QString)'),
>  lambda value: self.optionChanged('bar', value))
>
> layout = QVBoxLayout()
> layout.addWidget(fooEdit)
> layout.addWidget(barEdit)
>
> self.setLayout(layout)
>
> def optionChanged(self, option, value):
> self.values[option] = value
> print self.values
>
> def main(args):
> app = QApplication(args)
> values = dict(foo='', bar='')
> dialog = Options(values)
> dialog.show()
> app.exec_()
>
> if __name__ == '__main__':
> main(sys.argv)
>
>
> If I type a character in fooEdit, another character in barEdit, and
>> then
> delete the character from barEdit I get an unhandled win32 exception
> occured
> in python.exe on windows and segfault on linux.
>
> If I type a character in fooEdit, delete it, and then type a
character
> in

> barEdit I get:
>
> {'foo': PyQt4.QtCore.QString(u'a'), 'bar': ''}
> {'foo': PyQt4.QtCore.QString(u''), 'bar': ''}
> {'foo': Traceback (most recent call last):
>   File "L:\home\dev\python\test.py", line 17, in 
> lambda value: self.optionChanged('bar', value))
>   File "L:\home\dev\python\test.py", line 27, in optionChanged
> print self.values
> MemoryError
>
> I'm using Python 2.5.4 and PyQt 4.4.3-1
>
> Thanks in advance for any help.

 Works fine for me with current versions.

 Phil
>>>
>>> I have noticed that if I do "self.values[option] = QString(value)"
>>> instead of "self.values[option] = value" in optionChanged I don't get
>>> any
>>
>>> errors.
>>>
>>> Is it perhaps not safe to keep the reference to the lambda QString
>>> argument?
>>
>> It shouldn't make any difference.
>>
>> Phil
> 
> Last idea, C++ declaration of textChanged signal is this:
> 
> void textChanged (const QString&text)
> 
> would self.values[option] = value store the reference to QString? And if
so
> 
> is that safe, to access that object after my slot returns?
>
> As far as I can see C++ equivalent would be
> 
> QString* pointer = &text; then derferencing that pointer later in the
code.
> 
> I can see how this could cause problems.

If there was a bug with lambda slots it's been fixed by now.

> Btw you are using PyQt 4.4.4 correct? What version of python? 

PyQt v4.5 snapshot, Python v2.6.2 and v3.0.1.

Phil
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Re: How can I get Tkinter to work in Python? (I tried many things)

[Peter Pearson]

On Mon, 27 Apr 2009 17:49:26 -0700 (PDT), tom...@gmail.com wrote:
[snip]
> There are errors, but since there is many of them:
> here is a cut out of the _tkinter errors:
>
> libpython2.6.a(_tkinter.o): In function `Tkapp_CallProc':
> /home/tomzam/mylib6/Python-2.6.2/./Modules/_tkinter.c:1263: undefined
> reference to `Tcl_MutexLock'

I believe this message means that something named _tkinter.c
was previously compiled into an object file named
_tkinter.o, which was bundled into a library named
libpython2.6.a; and that when you attempt to use
libpython2.6.a to satisfy the external references of something
(not identified) that you're trying to link, the linker
discovers that _tkinter.o contains a function Tkapp_CallProc
that (on line 1263 of _tkinter.c) attempts to call function
Tcl_MutexLock, but the linker can't find anything named
Tcl_MutexLock to satisfy it.

Tcl_MutexLock is probably *supposed* to be provided by some
Tcl runtime library, but not being very knowledgeable, I
don't know what library.  Just before the beginning of the
list of error messages, you'll probably find the command line
that's running the linker, and it probably names a bunch of
libraries, one of which is supposed to include Tcl_Mutexlock
but doesn't.  I apologize for being so vague; with any luck,
someone much smarter will come along soon.

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Re: Restart generator when it is exhausted.

[J. Cliff Dyer]

On Tue, 2009-04-28 at 10:41 +, Duncan Booth wrote: 
> Lacrima  wrote:
> 
> > If it is not possible what are common techniques to use iterator or
> > generator objects that allow restarting when it is needed?
> 
> The usual thing if you want to use the generator's output more than once  
> would be to convert the generator to a list, then you can iterate over it 
> as often as you want.
> 
> >>> a = ['a', 'b', 'c']
> >>> g = (i for i in a)
> >>> restartable = list(g)
> 
> If you want the output of the generator to potentially change each time you 
> iterate then you need to create a new generator.
> 

More verbosely, but without putting your generator in , you can use the
iterator protocol to create a reusable iterable:

An iterable is a class with an __iter__ method that returns an iterator.

So for example:

class Iterator(object):
def __init__(self, filename):
self.f = open(filename)

def __iter__(self):
return self

def next(self):
line = self.f.readline()
if not line:
raise StopIteration
return line.strip()[:8]

is an iterator (which is also an iterable), which will grab each line of
a file, returning the first eight non-whitespace characters until the
file is used up.  Then the iterator is exhausted, and will continue to
raise StopIteration each time it is called.

class Iterable(object):
def __init__(self, filename):
self.filename = filename

def __iter__(self):
return Iterator(self.filename)

This is a reusable iterable which returns a new instance of the Iterator
class above each time it is exhausted.

So given a file hello.txt:

  Hello world
Hola mundo
  Guten tag, weld.

The classes can be used as followed:
>>> iterator = Iterator('hello.txt')
>>> for i in xrange(3):
>>> print "*** %d ***" % i
>>> for j in iterator:
>>> print j
*** 0 ***
Hello wo
Hola mun
Guten ta
*** 1 ***
*** 2 ***
>>> iterable = Iterable('hello.txt')
>>> for i in xrange(3):
>>> print "*** %d ***" % i
>>> for j in iterable:
>>> print j
*** 0 ***
Hello wo
Hola mun
Guten ta
*** 1 ***
Hello wo
Hola mun
Guten ta
*** 2 ***
Hello wo
Hola mun
Guten ta

When Iterator hits a StopIteration, it passes out of the inner loop, and
when it comes back in, the inner loop calls iterator.__iter__(), and
gets the same exhausted iterator (which immediately breaks the inner
loop by raising StopIteration).  In Iterable, when the loop calls
iterable.__iter__(), it gets a fresh iterator, so it can loop over the
file again.

The important thing is that when you call x.__iter__() (which you do
when entering a loop), you get a fresh iterator that won't just call
StopIteration right away.

Cheers,
Cliff


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Re: suggestion on a complicated inter-process communication

[Way]

Thanks a lot for reply. I understand it is abnormal to implement such
IPC, while it is worthy for my application.

Well, my process3 and 4 are from an outside application, which both
need License Check and os.system to involk.

>From my experience, if Process5 involks Process3, such License Check
can be very very slow (even slower than its real run).

That is why I need to separate Process3 and 4 onto different processes
to proceed.

On Apr 28, 1:57 am, Jonathan Gardner 
wrote:
> On Apr 27, 8:59 pm, Way  wrote:
>
>
>
> > Hello friends,
>
> > I have a little messy situation on IPC. Please if you can, give me
> > some suggestion on how to implement. Thanks a lot!
>
> > -> denotes create
>
> > MainProcess -> Process1 -> Process3 (from os.system)
> >                    |
> >                     -> Process2 (from os.system) -> Process4 (from
> > os.system) ->Process5
>
> > I would like to make the communication between Process1 and Process5.
> > Process1 needs Process5's output to provide argument to generate
> > Process3, and in turn Process5 needs to wait Process3 finished.
>
> > Thank you very much if you can give a hint.
>
> Abstraction should resolve this. What I mean is that Process2
> shouldn't be defined in terms of what it actually does, but what it
> appears to do. If you look at each process and think only what its
> child processes do and what its parent process expects it to do, then
> your job should get a lot simpler. Process1 expects Process2 to
> deliver a set of parameters to spawn Process3, and then it will wait
> until Process3 terminates.
>
> Looking at it this way, questions come to mind: Why can't Process2 run
> Process3 itself? It's unusual to have one process tell another process
> what to do when it can simply do it itself.
>
> By the way, I've never seen a time when this kind of design is
> necessary. There are other ways around your problem than spawning a
> bunch of processes. Each process should really be independent of all
> the other processes, doing only a very well-specified task in a well-
> specified way. The only time I could think of doing something like
> this is when you're getting a webserver setup and Process5 needs to
> communicate with Process3 to render the page or something like that.
> But even in that case, each process is really independently defined
> and implemented.

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Re: What do you think of ShowMeDo

[tuxagb]

On 28 Apr, 17:09, Astley Le Jasper  wrote:
> Hi,
>
> I've just stumbled over this (http://showmedo.com/) and being the very
> visual person I am, it seems like it could be a good way to learn
> about python. However, before I smack down $60, I wondered if anyone
> had any opinions on it. My gut feel is that it could be pretty good.
>
> ALJ

It can be useful, but there are many free howtos and tutorial ... and
the programming
can't be learned with video, but with books!

Hi.
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Re: suggestion on a complicated inter-process communication

[Way]

Thanks a lot for the reply. I am not familiar with multi-process in
Python. I am now using something like:
A_prog is an os.system to involk Process3
B_prog is an os.system to involk Process4
---
In Main Process:
Process1 = Popen(["A_prog"], stdin=PIPE, stdout=PIPE)
Process2 = Popen(["B_prog"], stdin=PIPE, stdout=PIPE)

cmd = Process2.stdout.readlines()
Process1.stdin.write(cmd)
if Process1.poll():
  Process2.stdin.write("trig from Process1")

-
In Process5 (another python program):
import sys
sys.stdout.write("process1 argument")
while 1:
if sys.stdin.readline().strip() == "trig from Process1":
break
--

However, in this case, Process5's stdout cannot be passed to
MainProcess for Process1, since it has not finished (waiting Process.
1/3 finish).

I am now using Fifos (an external file) to inter-communicate Process1
and 5. But at first run, it compliants "not file found".

Is there any possible solution to make it work? Thank you very much!

On Apr 28, 1:34 am, Aaron Brady  wrote:
> On Apr 27, 10:59 pm, Way  wrote:
>
>
>
> > Hello friends,
>
> > I have a little messy situation on IPC. Please if you can, give me
> > some suggestion on how to implement. Thanks a lot!
>
> > -> denotes create
>
> > MainProcess -> Process1 -> Process3 (from os.system)
> >                    |
> >                     -> Process2 (from os.system) -> Process4 (from
> > os.system) ->Process5
>
> > I would like to make the communication between Process1 and Process5.
> > Process1 needs Process5's output to provide argument to generate
> > Process3, and in turn Process5 needs to wait Process3 finished.
>
> > Thank you very much if you can give a hint.
>
> The 'mmap' module can help with getting the data from 5 to 1.  It
> requires creating a file.  If it's a small amount of data, any old
> file will do.  You may need a socket in order to wait for Process3 to
> join, or write a small '.pyd' or '.so' file that gives you access to
> your system's synchronization object.

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Re: How to locate the bit in bits string?

[tuxagb]

On 28 Apr, 17:24, Li Wang  wrote:
> 2009/4/29 Tim Chase :
>
> > Li Wang wrote:
>
> >> Hi:
>
> >> If I use an integer to represent bits:
> >> e.g. 99 represents '1100011'
>
> >> How can I locate, say the second bit of 99(i.e. '1')?
>
> >> Although bin(99)[4] could be used to locate it, this transform cost
> >> too much memory (99 only needs 2Bytes, while string '1100011' needs
> >> 7Bytes).
>
> >> Anyone knows how to locate  the second bit without using bin() function?
>
> > You mean
>
> >  def get_bit(number, bit):
> >    return (number >> bit) & 1
>
> > ?
>
> Hummm, I have tried this method too, the problem is its time
> complexity. If the length of my bits is n, then the time complexity is
> O(n). When I tried to implement this in practice, it did consume a lot
> of time.
>
> So do you know how could I locate the bit in O(1) time? Transform it
> into a string is a method, but takes too much space (when I try to
> process a 2M file, it used more than 100M memory.).
>
> Thank you very much.
>
> > -tkc
>
> --
> Li
> --
> Time is all we have
> and you may find one day
> you have less than you think

The my solution is good, but the Tim's solution is better, and it is O
(1) in time and space.
What is you search? I dont'know you general problem, but search the
value of a bit in a 2M file ...
is strange .

Hi.
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Re: suggestion on a complicated inter-process communication

[norseman]

Way wrote:

Hello friends,

I have a little messy situation on IPC. Please if you can, give me
some suggestion on how to implement. Thanks a lot!

-> denotes create


MainProcess -> Process1 -> Process3 (from os.system)
   |
-> Process2 (from os.system) -> Process4 (from
os.system) ->Process5

I would like to make the communication between Process1 and Process5.
Process1 needs Process5's output to provide argument to generate
Process3, and in turn Process5 needs to wait Process3 finished.

Thank you very much if you can give a hint.

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=

My first reaction is to use named pipes.

Process1 -> P2 -> P4 -> Process5 >>NamedPipe (P5 outputs to NamedPipe)
   Process1 waits for NamedPipe to be made and starts creating Process3
   When Process3 is finished it can set an OS level environmental or
 create a dummy file as a signal to Process5 to finish.
   P1 becomes orchestrator, NamedPipe is courier, file is smoke signal.

This method works when IPC is not a good choice. (Like independent child 
processes run across the net. A specific file in a specific location 
effectively creates a specific signal. Whether or not contents are used 
or even existing is programmer choice.)


Hope this helps.

Steve
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Re: Getting the "dir" from the other ancestor ?

[Stef Mientki]

tuxagb wrote:

On 28 Apr, 15:01, Stef Mientki  wrote:
  

hello,

I have a class, derived from some user defined class
(User_Defined_Ancestor) and some basic class (Basic_Ancestor).

One of the major tasks of the Basic_Ancestor,
is to hide all kinds of implementation details for the user,
so the user can concentrate on the functional design.

One of things I need to know are the methods and attributes of the
Basic_Ancestor.
Both classes are dynamic, i.e. attributes are added during run time.

class Master ( User_Defined_Ancestor, Basic_Ancestor ) :
def __init__ ( self, *args, **kwargs ) :
Basic_Ancestor.__init__ ( self, *args, **kwargs )
.

class Basic_Ancestor ( object ) :
def __init__ ( self,  ) :
self.other = dir ( User_Defined_Ancestor )

def Get_Attributes ( self ) :
return dir ( self ) - dir ( self.other )

Now the problem is, I don't know "User_Defined_Ancestor" in Basic_Ancestor.
I can't pass it through the parameter list, because I use "*args, **kwargs"
I possibly could use some global variable, but that's not my preference.

Any other suggestions ?

thanks,
Stef Mientki



In anytime, if you do dir() in a class B, that extends a class A, you
have all fields of A also.
  

That's exactly the problem I encounter ;-)
After some trial and error, I found this solution:

class Basic_Ancestor ( object ) :
   def __init__ ( self,  ) :
   # Collect all methods and attributes of other classes
   self.Exclude_Dir  = []
   Base_Classes = self.__class__.__bases__
   for BC in Base_Classes :
   if BC != My_Control_Class :
   self.Exclude_Dir += dir ( BC )


cheers,
Stef
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Re: suggestion on a complicated inter-process communication

[Paul Boddie]

On 28 Apr, 17:40, Way  wrote:
> Thanks a lot for reply. I understand it is abnormal to implement such
> IPC, while it is worthy for my application.
>
> Well, my process3 and 4 are from an outside application, which both
> need License Check and os.system to involk.

Sounds delightful!

Anyway, looking at your diagram (edited to fit)...

Main
 | \-> P1 -> P3 (from os.system)
 \-> P2 (from os.system) -> P4 (from os.system) ->P5

...if P1, P2 and P4 are able to propagate input and output, then this
is just a matter of having something in the main process which
monitors the input from P5 (via P4 and P2) and which relays the input
to P3 (via P1). This could be as simple as the following:

to_p1.write(from_p2.read())

If this isn't sophisticated enough, because you only want to read some
details from P2, you could either try and read a predetermined amount
from P2, or you could write a communications handler which monitors
the input from P2 using a select.poll object. If the main process is
supposed to be doing other things, then it's quite likely that you'll
have to do something involving either select.poll or threads, anyway.

Paul
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stuck with PyOBEX

[alejandro]

So I installed the module and tryed to make it work but...
It gave me:

Traceback (most recent call last):
  File "first.py", line 24, in 
client2.connect()
  File "C:\Python25\lib\PyOBEX\client.py", line 359, in connect
return Client.connect(self, header_list = [headers.Target(uuid)])
  File "C:\Python25\lib\PyOBEX\client.py", line 119, in connect
self.socket = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM,
AttributeError: 'module' object has no attribute 'AF_BLUETOOTH'>>> Exit 
Code: 1


This module asks the socket module for AF_BLUETOOTH... in the socket module 
there is no such thing as AF_BLUETOOTH. Could it be that the person that 
made PyOBEX modified his socket module and forgot to give his socket module? 
Or am I missing something? Maybe AF_BLUETOOTH stands for something that a 
programmer would know but I am a beginner so...

Is there a OBEX module for Python on windows?


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Re: Light (general) Inter-Process Mutex/Wait/Notify Synchronization?

[John Nagle]

Gunter Henriksen wrote:

If you don't want to use a 3rd party module you could
use the multiprocessing module


That is definitely good for when I have a tree of
processes which are all Python applications.  I use
it for that.  But I am looking for something where
the Python application can interact conveniently
with an arbitrary external application.  Using a
socket/pipe and shared memory is convenient, but
not feasible when system call overhead matters.


Linux doesn't do interprocess communication very well.
The options are pipes (clunky), sockets (not too bad, but
excessive overhead), System V IPC (nobody uses
that) and shared memory (unsafe).

If you want to see IPC right, what you really need is
the QNX microkernel, and its messaging system.  I've pumped
uncompressed video through the QNX messaging system and had
only 2% of the CPU devoted to message overhead.  The basic
primitives are MsgSend, MsgReceive, and MsgReply, which do
about what you'd expect and do it very fast.  Linux lacks
this.

   If you're using CPython, don't worry about socket overhead.
CPython is so slow you'll never notice it.

John Nagle
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Re: How to locate the bit in bits string?

[Tim Chase]

Li Wang wrote:

2009/4/29 Tim Chase :

Li Wang wrote:

If I use an integer to represent bits:

[snip]

Hummm, I have tried this method too, the problem is its time
complexity. If the length of my bits is n, then the time complexity is
O(n). When I tried to implement this in practice, it did consume a lot
of time.


I'm not sure I follow here -- your original post said that you 
have an integer.  With an integer, my function is O(1) as you 
request.  It sounds like you're *not* representing your bits as 
an integer.  Either that, or it's a gargantuan number (say, more 
than 64 bits?  Maybe more than 1k bits?) that you want to 
bit-slice.  In that case, you need to know a bit more about the 
storage structure.  However, assuming it's a raw bit-stream, you 
might be able to do something like this (untested, but should be 
fairly close)


  data = file('source.bin').read()
  def get_bit(source, bit):
idx, bit = divmod(bit, 8)
byte = ord(source[len(source) - (1+idx)])
return (byte >> bit) & 1

  print get_bit(data, 3141592) # the 3,141,592nd bit

you might have to tweak for endian'ness.

-tkc





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Re: Why bool( object )?

[Gabriel Genellina]

En Tue, 28 Apr 2009 09:22:01 -0300, Colin J. Williams   
escribió:

Lie Ryan wrote:

Aaron Brady wrote:



This makes it so all objects except False, None, 0, and empty
containers are true by default.  I am not convinced that 'if ' should have any meaning; it should probably throw an
exception.  Is it part of Python's look and feel or its mentality?  Is
it part of the Zen?  Certainly other ideal types can't be cast from
generic objects, so why booleans?  Is it an ineffable component of the
author's vision for the language?  I think that giving arbitrary
syntactic constructs meaning is just space-filler.  It's worse than
syntactic sugar, it's semantic sugar.  Why not assign meanings willy-
nilly to other random juxtapositions of tokens?


 It's part of the design decision. In almost all cases (in any  
language), a so-called "Design Decision" is rather random and prone to  
subjective judgment, just as the decision to make bool(int) returns  
False only on 0, -1, or for all negative values; whether to make  
bool(100) and exception or True; or round() rounds down or up or  
even-odd; or the use of brackets vs. indentation; or whether to treat  
empty list as True or False.


I'm puzzled by the last sentence:


bool(0)

False

bool(-1)

True

bool(-100)

True


That's the "design decision". bool(-1) *might* have been False, and  
bool(-100) *might* raise an exception. They behave the way they do because  
of a conscious decision.


To Aaron: "Programming language design is not a rational science. Most  
reasoning about is is at best rationalization of gut feelings, and at  
worst plain wrong."
(GvR in python-ideas:  
http://groups.google.com/group/python-ideas/msg/ac61f03c32578bae )


--
Gabriel Genellina

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Re: inside-out range function

[Scott David Daniels]

Steven D'Aprano wrote:

... I wrote a similar function to do this:

def monge_shuffle(deck):
if len(deck) % 2: # Odd number of items.
deck[:] = deck[0::2] + deck[1::2][::-1]
else: # Even number of items.
deck[:] = deck[1::2] + deck[0::2][::-1]
return deck


Oooh, shiny fun!!!  How's this for that:

def monge_shuffle2(deck):
even = (len(deck) ^ 1) & 1
return deck[even::2] + deck[-2::-2]

--Scott David Daniels
scott.dani...@acm.org
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Re: suggestion on a complicated inter-process communication

[Paul Boddie]

On 28 Apr, 17:44, Way  wrote:
> Thanks a lot for the reply. I am not familiar with multi-process in
> Python. I am now using something like:
> A_prog is an os.system to involk Process3
> B_prog is an os.system to involk Process4
> ---
> In Main Process:
> Process1 = Popen(["A_prog"], stdin=PIPE, stdout=PIPE)
> Process2 = Popen(["B_prog"], stdin=PIPE, stdout=PIPE)
>
> cmd = Process2.stdout.readlines()

Careful here: this may want to read until process 2 has closed its
stream, which may only occur on exit, normally.

> Process1.stdin.write(cmd)
> if Process1.poll():
>   Process2.stdin.write("trig from Process1")
>
> -
> In Process5 (another python program):
> import sys
> sys.stdout.write("process1 argument")

Careful here, too: this output may not be sent immediately, due to
buffering issues.

> while 1:
>     if sys.stdin.readline().strip() == "trig from Process1":
>             break

And this test may not be satisfied, since the main process may still
be waiting for output from process 5 (via process 2), not reaching the
point where it writes a response.

Paul
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Re: stuck with PyOBEX

[Diez B. Roggisch]

alejandro wrote:

> So I installed the module and tryed to make it work but...
> It gave me:
> 
> Traceback (most recent call last):
>   File "first.py", line 24, in 
> client2.connect()
>   File "C:\Python25\lib\PyOBEX\client.py", line 359, in connect
> return Client.connect(self, header_list = [headers.Target(uuid)])
>   File "C:\Python25\lib\PyOBEX\client.py", line 119, in connect
> self.socket = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM,
> AttributeError: 'module' object has no attribute 'AF_BLUETOOTH'>>> Exit
> Code: 1
> 
> 
> This module asks the socket module for AF_BLUETOOTH... in the socket
> module there is no such thing as AF_BLUETOOTH. Could it be that the person
> that made PyOBEX modified his socket module and forgot to give his socket
> module? Or am I missing something? Maybe AF_BLUETOOTH stands for something
> that a programmer would know but I am a beginner so...
> 
> Is there a OBEX module for Python on windows?

AF_BLUETOOTH seems to be specific to *nix-systems. At least under debian and
ubuntu, I've got it defined.

So it seems it is not supported under windows - you should consider the
author if that's a mistake, or by design.

Diez
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Re: Connecting/talking to OpenOffice Base files

[norseman]

deostroll wrote:

Hi,

I was wondering if the python interpretor can talk to files with
extension *.odb (OpenOffice Base files). They are like flat database
files, similar to Microsoft Access files. I want to store data into
them as well as extract data out of them.

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=
No and Yes.

Python cannot, as far as I know, do direct read/write to the file proper.

Python can talk to OOo via a OOo type of COM setup, by way of which 
Python can send OOo commands to do things.  My personal experience with 
this has shown me that OOo docs on the subject are 'a bit light' in both 
narrative and example.


Suggestions:
1) Go to  www.openoffice.org  and look for UNO (OOo's COM)
2) Check out whatever seems best for you.
3) Do not expect much help, People or docs, from OOo.
4) To use the UNO you will need to use the OOo package supplied
 python.  Set up a wrapper to change to their environment
 and start their python from it.  Otherwise expect chaos.

5) Use the make macro builtins and save as python. Use those as
 the base to work from.  You MUST have OOo running BEFORE
 trying to link an outside Python process.

Hope you have a better experience with them than I did.


Steve


A sample that does function. How valid?  I'm not sure. :)

#!/bin/bash /opt/openoffice.org2.0/program/python.sh
#  on my system, above actually works if this file is chmod 755
#  A TEST
#  SLT
#  September, 2008
#
#  works - sort of: the writer functions, although badly.
# there are no examples of cursor placement in text.
#   the calc functions, but saveas .csv is NOT text
# it winds up OOo-PKzipped on disk.
#  I have yet to find where the verbs below come from.  OOo docs are
#among the world's worst, in my opinion.  In order to get this
#to work at all I had to go to third party locations and horse
#around until I found a combination that worked.
#  While I'm no fan of Microsoft;
#  If you need automation in your office endeavors, Use Microsoft.
#At least it works with less effort and has some help to be found
#on the web.  SUN seems to be sponsoring it's own demise.  I guess
#they hired too many Microsoft loyalists.
#
#  DOWN BELOW:  change paths and files to suit your system.
#
#  I know this prints ugly on paper. Blame it on children liking long
#words, presumably preferring increased typos too...
#

import os
import sys
import popen2
import time
import uno

pgm_in, pgm_out, pgm_err = popen2.popen3("scalc 
accept=socket,host=localhost,port=2002\;urp\; &")



## if you use soffice in above line, program is likely to crash.
##   it will not open generic txt files.
## for scalc, use that name above. for swriter, use that name above.

time.sleep(10)
## OOo and uno need time to activate.  Otherwise whole thing bombs.

local = uno.getComponentContext()
resolver = 
local.ServiceManager.createInstanceWithContext("com.sun.star.bridge.UnoUrlResolver", 
local)
context = 
resolver.resolve("uno:socket,host=localhost,port=2002;urp;StarOffice.ComponentContext")
OOoAPP = 
context.ServiceManager.createInstanceWithContext("com.sun.star.frame.Desktop", 
context)


comment= """
##for
OOoDOC = OOoAPP.loadComponentFromURL("file:///mnt/mass/py/zz.txt" 
,"_blank", 0, ())

##  line above can blow up. soffice doesn't handle generic text/names at
##all in this method of endeavor. Not even .txt extensions
##  must start swriter, not soffice, if a generic text open is to succeed.

OOoDOC = OOoAPP.getCurrentComponent()
cursor = OOoDOC.Text.createTextCursor()
OOoDOC.Text.insertString(cursor, "This text is being added to openoffice 
using python and uno package.", 0)

OOoDOC.Text.insertString(cursor, "\n\nThis is a new paragraph.", 0)
OOoDOC.storeAsURL("file:///mnt/mass/py/zz-tst.txt",())
##next
"""
#for
SPRDSHT1 = OOoAPP.loadComponentFromURL("file:///mnt/mass/py/x.xls" 
,"_blank", 0, ())

SPRDSHT = OOoAPP.getCurrentComponent()
##cursor = SPRDSHT.Text.createTextCursor()
#SPRDSHT.storeAsURL("file:///mnt/mass/py/x-tst.csv",("Text - txt - csv 
(StarCalc)"))
# ran, loaded, no-save 
SPRDSHT.storeToURL("file:///mnt/mass/py/x-tst.csv",SPRDSHT._toProperties(FilterName="Text 
- txt - csv (StarCalc)"))
SPRDSHT.exportToURL("file:///mnt/mass/py/x-tst.csv",("Text - txt - csv 
(StarCalc)"))



SPRDSHT.dispose()
##next

OOoAPP.dispose()
##  it may take several minutes for 'blank' to unload itself. Then too,
##  this may leave the 'blank' hanging. If so, stop it manually before
##trying to use this again.
##
##  if you have to kill it, run soffice manually and close it manually
##before attempting to use it again. Otherwise things get worse.
#  end of test

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Re: Third Party Modules

[John Nagle]

Brock wrote:

Hi Everyone,

I know this is most likely a basic question and you will roll your
eyes, but I am just starting out with Python (hobbyist) and I see many
tutorials on the web referring to the use of external modules.

However, when I locate them, they often come as a zipped folder with a
number of files.  How do I install them?  In addition, is there an
easy way to manage external modules? Some I see require additional
modules not included.


   There are several different mechanism for handling this, and they all suck.
The whole Python module distribution scheme is so uncoordinated that there's
no uniform way to do this.  It's not your fault.

   There's "python ./setup.py".  There are "eggs", which are supposed to
install very simply, but in practice usually fail to install properly,
producing obscure error messages.  There are Windows installers.
There's no consistency.

   I'm currently struggling with guiding users through installation
of a Python program I put on SourceForge. I have to explain to them how
to install three different external modules which don't have compatible
installation mechanisms.

   I'm not going to put Python software out for public use again.  I don't
have the time to deal with this crap.

John Nagle
Animats
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Re: Why bool( object )?

[Scott David Daniels]

Steven D'Aprano wrote:

On Mon, 27 Apr 2009 23:11:11 -0700, Aaron Brady wrote:
... In a boolean (or truth) context, Something and Nothing behave like True

> and False in languages with real booleans:

if obj:
print "I am Something"
else:
print "I am Nothing"


If you define the short-circuit boolean operators "and" and "or" as
Python does, the idea of "most anything is True" menas you can have
code that does:
v = look('here') or look('there') or look('everywhere') or default

This is a nice idiom, and the "or default" can be used in lots of cases.

--Scott David Daniels
scott.dani...@acm.org
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Re: stuck with PyOBEX

[alejandro]

Can you tell me what is it? Maybe I can search it and pass it in another 
way... if it is an address or protocol name

> AF_BLUETOOTH seems to be specific to *nix-systems. At least under debian 
> and
> ubuntu, I've got it defined.
>
> So it seems it is not supported under windows - you should consider the
> author if that's a mistake, or by design.
>
> Diez 


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Re: How to locate the bit in bits string?

[Tim Chase]

 data = file('source.bin').read()
 def get_bit(source, bit):
   idx, bit = divmod(bit, 8)
   byte = ord(source[len(source) - (1+idx)])
   return (byte >> bit) & 1


My understanding is: when doing this step, every bit in the byte will
be shifted bit-long. If it is get_bit(data, 100), and the source.bin
has 200bits in it. this single step (i.e. return (byte >> bit) & 1)
will take 200 + 199 + 198 + ... + 101 times bit shifting operation.
That's my understanding of the this function.



The function extracts the byte that contains the bit of interest, 
and then extracts the corresponding bit from that byte.  More 
verbosely:


  idx, bit = divmod(bit, 8)
  # idx is now the Nth byte from the end we want
  # bit is now 0-7 for the bit inside the corresponding byte

  offset = len(source) - (1+idx)
  # convert the left-hand idx to a right-hand idx

  byte = ord(source[offset]))
  # we now have the byte containing the bit we want

  # my original O(1) bit-extract
  return (byte >> bit) & 1

it only shifts once because it can precisely target the exact 
byte without having to visit the other bytes.  Trust me...it's 
O(1) for extracting a single bit (unless indexed access to "data" 
is not O(1), but that would assume something other than a string 
or list data-type...like a data-stream or generator).


-tkc




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Re: Web framework for embedded system

[Scott David Daniels]

Thomas Heller wrote:

I'm looking for a lightweight web-framework for an embedded system.
The system is running a realtime linux-variant on a 200 MHz ARM
processor, Python reports a performance of around 500 pystones

> Does this sound sensible at all? Any suggestions?

Look at this talk from PyCon:
Title:
Batteries Included! Python on Low Cost Tiny Embedded Wireless Devices
   http://blip.tv/file/1947528

You might want to try contacting them.

--Scott David Daniels
scott.dani...@acm.org
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Re: stuck with PyOBEX

[Diez B. Roggisch]

alejandro wrote:

> Can you tell me what is it? Maybe I can search it and pass it in another
> way... if it is an address or protocol name

I'm not entirely sure, but I guess no, you can't simply pass it in.

Unix uses streams as abstraction for a lot of things - all kinds of devices
for example.

Windows doesn't. It most probably has a dedicated API for dealing with
bluetooth - I found this document which backs this assumption:

http://tombell.org.uk/papers/bluetooth-detection.pdf

I can't comment on the feasibility of hooking the windows api into the inner
workings of PyOBEX - depending on it's design, it would be a major
overhaul.

Diez
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bug with os.rename in 2.4.1?

[t123]

I was wondering if anyone has seen this problem before?

I have a job that runs hourly.  Part of the processing is to rename a
file using os.rename.  The file name is the same every hour.
Sometimes the os.rename fails and the file does not get renamed.  It
only happens occasionally.  Most of the time it works just fine.

Appreciate any ideas.

Thanks
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Re: Light (general) Inter-Process Mutex/Wait/Notify Synchronization?

[Gunter Henriksen]

> Linux doesn't do interprocess communication very well.
> The options are [...] and shared memory (unsafe).

I think the bar has to be set pretty high to say shared memory
is too unsafe an approach for active entities to communicate.


> If you're using CPython, don't worry about socket overhead.
> CPython is so slow you'll never notice it.

It is not so much the socket overhead as the context switch.
If processes could send data to each other through sockets
without making system calls, that would be great.
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Re: python segfaulting, MemoryError (PyQt)

[Denis L]

"Phil Thompson"  wrote in message 
news:mailman.4699.1240932385.11746.python-l...@python.org...

> If there was a bug with lambda slots it's been fixed by now.

I just tried it and I'm getting the same errors with regular functions.

Could you try running the code bellow? What output you are getting when 
barTextChanged is called?

On my system self.foo and text point to the same QString object.

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Options(QDialog):
def __init__(self):
QDialog.__init__(self)

fooEdit = QLineEdit()
self.connect(fooEdit, SIGNAL('textChanged(QString)'),
 self.fooTextChanged)

barEdit = QLineEdit()
self.connect(barEdit, SIGNAL('textChanged(QString)'),
 self.barTextChanged)

layout = QVBoxLayout()
layout.addWidget(fooEdit)
layout.addWidget(barEdit)
self.setLayout(layout)

def fooTextChanged(self, text):
self.foo = text

def barTextChanged(self, text):
print self.foo, text, id(self.foo), id(text)

def main(args):
app = QApplication(args)
dialog = Options()
dialog.show()
app.exec_()

if __name__ == '__main__':
main(sys.argv)


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