Re: [Tutor] Bad time to get into Python?
Dotan Cohen wrote: > However, with the coming of Python3 and the new syntax, is this a bad time to > start learning Python? Not at all, I'd say. Changes will be fairly small, with the main changes being: - print is replaced by a print() function - / will become the float division operator - changes towards iterators (e.g. range() doesn't return a list) - string filetype changes There are lots of other changes, but most of them include removing already deprecated idioms. [1] has a list of Python 3k changes. There's also the 2to3 conversion tool which allows you to run lots of conversion automated. > That asked, I've heard that 2.6 can be configured to warn when using > code that will not run in 3.x. Is this correct? Yes, 2.6 will support a "Py3k warnings mode". It should also have many of 3k's features already implemented, allowing to run both side-by-side or via __future__. PEP 3000 ([2]) has more info on this. > How is this done? I'd like to do it on a per-file basis, so that I will > only need to run one version of python on this machine. Don't know. But if your only using it for some home-coding, you would just once do the conversion and then update to 3k. > I want my own apps to throw errors, > but not other python apps on this system. Is there some error-level > code that I can run? Not sure what you mean by that. Are you refering to exception-handling? I'd say it's not a bad time to learn Python. There will be some major changes in 3k, but as long as you don't have to maintain 2.6 and 3.0 in parallel, conversion should be easy enough. Cheers, thomas pani [1] http://docs.python.org/dev/3.0/whatsnew/3.0.html [2] http://www.python.org/dev/peps/pep-3000/ ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] opening a pipe?
The subprocess module is what you're looking for.
Your example would look like
%<
import subprocess
p = subprocess.Popen('cat hi.txt', shell=True, stdout=subprocess.PIPE)
for line in p.stdout:
print line
%<
I assume you know that you can just open a file for reading instead of
piping cat.
thomas
James Hartley wrote:
> A Perl script can easily serve as a filter within a pipe as seen in
> the following:
>
> use strict;
> use warnings;
>
> open(IN, 'cat hello.txt |') or die 'unable to open file';
> while () {
> print;
> }
> close(IN);
>
> Can I do the same within Python? Thanks.
>
> Jim
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Re: [Tutor] Question on multithreading
Hi, Here are some thoughts: From the Python Library Reference: "If the subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init__()) before doing anything else to the thread." You'll have to do that for your GuiScript class. You can't just stop a thread, you can only wait for it to finish using join(). Or you can set its deamon flag, so it will exit when no non-daemon threads are left. Is there any reason for starting the GUI code in a separate thread? You could just leave it in the main thread. For some general notes on this topic this might be helpful: http://wiki.wxpython.org/LongRunningTasks Cheers, Thomas Pani Varsha Purohit wrote: > Hello, > i have a gui program in wxpython where i am spawning two threads. > one for the mainloop of gui and other for some background tasks. I have > to stop the background running thread once its work is done. I am trying > to use the join method but it is giving me an error saying threads > cannot be joined as the thread has just been created... whereas at that > point the thread is done with its job. So i am confused whether i am > putting it correctly or not. also, is there any method called stop() to > stop the threadsAlso, i want to see if the thread is alive or not.. > but i donno where should i put the isAlive() method associated with the > thread.. i tried putting it in the code where thread does execution but > apparently it is not the correct place. > > Here is the code... > > class GuiScript(threading.Thread): > def __init__(self): > self.run() > def run(self): > app = wx.PySimpleApp() > MainWindow().Show() > app.MainLoop() > > class RunScript(threading.Thread): > def run(self): > imFile=test() > > and when the stop button is pressed the two threads should stop > executing... so i have written code like this... > > def OnCloseWindow(self,event): > GuiScript().Stop() > RunScript().Stop() > self.Destroy() > > but seems stop() method is not existing... can anybody guide me pl > > thanks, > > > -- > Varsha Purohit, > Graduate Student > > > > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Open a directory in the default file manager
Tim Michelsen wrote: > Hello, > is there any function/module that allows me to open a directory in the > default file manager of a operating system? On Windows you can use os.startfile(). On "pure" Unices there's no such thing as filetype associations However, if you use a desktop environment, you can spawn xdg-open (from xdg-utils) from Python. This will autodetect gnome, kde and xfce and use their tools (gnome-open, kfmclient, exo-open). I think on OS X/Darwin there's a similar utility called `open'. You can use sys.platform to determine which system you're running on. thomas ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] listing classes
Hi,
dir(A) will essentially give you what you want (and a little more)
If you're only interested in classes, you can do something like:
import types
[ name for name in dir(A) if type(eval('A.'+name)) == types.ClassType ]
Thomas
Laureano Arcanio wrote:
Hi All,
I need to have a listing of all classes defined inside a class body,
something like this:
class A(object):
class B(object):
pass
class C(object):
pass(object):
and i need to get the classes to instantiate them.. something like this.
classes =[A,B]
Any ideas ? do i need meta classes or something ?
Thanks in advice.
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Re: [Tutor] Decimals 'not equal to themselves' (e.g. 0.2 equals 0.200000001)
CNiall wrote:
I want to make a simple script that calculates the n-th root of a given
number (e.g. 4th root of 625--obviously five, but it's just an example
:P), and because there is no nth-root function in Python I will do this
with something like x**(1/n).
Side note: of course there are python built-in ways to do that. You just
named one yourself:
In [6]: 625**(1.0/4)
Out[6]: 5.0
also:
In [9]: pow(625, 1.0/4)
Out[9]: 5.0
However, with some, but not all, decimals, they do not seem to 'equal
themselves'.
As you can see, the last two decimals are very slightly inaccurate.
However, it appears that when n in 1/n is a power of two, the decimal
does not get 'thrown off'. How might I make Python recognise 0.2 as 0.2
and not 0.20001?
You just can't store 0.1 as a binary floating point.
You might want to read:
http://www.network-theory.co.uk/docs/pytut/FloatingPointArithmeticIssuesandLimitations.html
http://www.network-theory.co.uk/docs/pytut/RepresentationError.html
The decimal module provides decimal floating point arithmetic:
http://docs.python.org/lib/module-decimal.html
like in:
In [1]: 0.2 * 2
Out[1]: 0.40002
In [2]: from decimal import Decimal
In [3]: Decimal('0.2') * 2
Out[3]: Decimal("0.4")
thomas
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