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Re: Why doesn't Python remember the initial directory?

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2012/8/20 kj <no.email@please.post>:
> In <roy-CA6D77.17031119082012@news.panix.com> Roy Smith <roy@panix.com> writes> This means that no library code can ever count on, for example,
> being able to reliably find the path to the file that contains the
> definition of __main__.  That's a weakness, IMO.  One manifestation
> of this weakness is that os.chdir breaks inspect.getmodule, at
> least on Unix.  If you have some Unix system handy, you can try
> the following.  First change the argument to os.chdir below to some
> valid directory other than your working directory.  Then, run the
> script, making sure that you refer to it using a relative path.
> When I do this on my system (OS X + Python 2.7.3), the script bombs
> at the last print statement, because the second call to inspect.getmodule
> (though not the first one) returns None.
>
> import inspect
> import os
>
> frame = inspect.currentframe()
>
> print inspect.getmodule(frame).__name__
>
> os.chdir('/some/other/directory') # where '/some/other/directory' is
>                                   # different from the initial directory
>
> print inspect.getmodule(frame).__name__
>
> ...............
>
> % python demo.py
> python demo.py
> __main__
> Traceback (most recent call last):
>   File "demo.py", line 11, in <module>
>     print inspect.getmodule(frame).__name__
> AttributeError: 'NoneType' object has no attribute '__name__'
>
>..

As in many other cases the programming language can't possibly act
safely on all the possible stupid things that the programmer wants to
do, and not understanding how an operating system works doesn't help
either..

In the specific case there is absolutely no use of os.chdir, since you
can:
- use absolute paths
- things like subprocess.Popen accept a cwd argument
- at worst you can chdir back to the previous position right after the
broken thing that require a certain path that you are calling is run

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Why doesn't Python remember the initial directory? kj <no.email@please.post> - 2012-08-19 20:42 +0000
  Re: Why doesn't Python remember the initial directory? Giacomo Alzetta <giacomo.alzetta@gmail.com> - 2012-08-19 14:01 -0700
    Re: Why doesn't Python remember the initial directory? Nobody <nobody@nowhere.com> - 2012-08-20 01:45 +0100
      Re: Why doesn't Python remember the initial directory? Neil Hodgson <nhodgson@iinet.net.au> - 2012-08-21 11:39 +1000
  Re: Why doesn't Python remember the initial directory? Roy Smith <roy@panix.com> - 2012-08-19 17:03 -0400
    Re: Why doesn't Python remember the initial directory? kj <no.email@please.post> - 2012-08-20 01:57 +0000
      Re: Why doesn't Python remember the initial directory? Jerry Hill <malaclypse2@gmail.com> - 2012-08-19 22:05 -0400
      Re: Why doesn't Python remember the initial directory? alex23 <wuwei23@gmail.com> - 2012-08-19 19:57 -0700
        Re: Why doesn't Python remember the initial directory? alex23 <wuwei23@gmail.com> - 2012-08-19 20:04 -0700
          Re: Why doesn't Python remember the initial directory? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-20 08:11 +0100
        Re: Why doesn't Python remember the initial directory? alex23 <wuwei23@gmail.com> - 2012-08-19 20:03 -0700
        Re: Why doesn't Python remember the initial directory? alex23 <wuwei23@gmail.com> - 2012-08-19 19:59 -0700
        Re: Why doesn't Python remember the initial directory? Paul Rubin <no.email@nospam.invalid> - 2012-08-20 21:20 -0700
      Re: Why doesn't Python remember the initial directory? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-20 03:38 +0000
        Re: Why doesn't Python remember the initial directory? alex23 <wuwei23@gmail.com> - 2012-08-19 20:43 -0700
      Re: Why doesn't Python remember the initial directory? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-20 08:10 +0100
      Re: Why doesn't Python remember the initial directory? andrea crotti <andrea.crotti.0@gmail.com> - 2012-08-20 12:56 +0100
        Re: Why doesn't Python remember the initial directory? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-20 13:14 +0000
          Re: Why doesn't Python remember the initial directory? Walter Hurry <walterhurry@lavabit.com> - 2012-08-20 13:49 +0000
            Re: Why doesn't Python remember the initial directory? Roy Smith <roy@panix.com> - 2012-08-20 09:58 -0400
              Re: Why doesn't Python remember the initial directory? andrea crotti <andrea.crotti.0@gmail.com> - 2012-08-20 15:15 +0100
      Re: Why doesn't Python remember the initial directory? Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-08-20 16:39 +0200
      Re: Why doesn't Python remember the initial directory? Grant Edwards <invalid@invalid.invalid> - 2012-08-20 16:28 +0000
      Re: Why doesn't Python remember the initial directory? Piet van Oostrum <piet@vanoostrum.org> - 2012-08-20 16:06 -0400
      Re: Why doesn't Python remember the initial directory? John Roth <johnroth1@gmail.com> - 2012-08-21 13:35 -0700
  Re: Why doesn't Python remember the initial directory? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-19 22:18 +0100
  Re: Why doesn't Python remember the initial directory? Laszlo Nagy <gandalf@shopzeus.com> - 2012-08-19 23:05 +0200
  Re: Why doesn't Python remember the initial directory? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-19 17:54 -0700

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