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Date: Sun, 11 Dec 2011 22:02:23 -0800
Subject: Re: subprocess question
From: Chris Rebert <clp2@rebertia.com>
To: jyoung79@kc.rr.com
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On Sun, Dec 11, 2011 at 8:39 PM,  <jyoung79@kc.rr.com> wrote:
> Wondering if anyone could shed some light on the subprocess module? =C2=
=A0I'll admit I'm not that great at the shell.
>
> If I was wanting to get the size of the trash (on OS X), I could use:
>
>>>> os.system('du -sh ~/.Trash/')
> =C2=A011M =C2=A0 =C2=A0/Users/jay/.Trash/
> 0
>
> Which gives me what I want. =C2=A0However, I've been reading that it's be=
tter to use subprocess. =C2=A0I did a test like so, but is this a good way =
to do this?
>
>>>> import subprocess
>>>> p =3D subprocess.Popen(['du', '-sh'], cwd=3D'/Users/jay/.Trash/', stdo=
ut=3Dsubprocess.PIPE)
>>>> out, err =3D p.communicate()
>>>> out
> ' 11M\t.\n'

You might prefer to use subprocess.check_output(); it slightly
simplifies your code:
http://docs.python.org/library/subprocess.html#subprocess.check_output

> And another question - why can't I use the tilde as a shortcut to the hom=
e directory?

Because ~ is interpolated by the shell and `subprocess` does not use
the shell by default for reasons that include efficiency and security.
You can expand ~ yourself using os.path.expanduser():
http://docs.python.org/library/os.path.html#os.path.expanduser
Alternatively, you can opt to use the shell by passing shell=3DTrue as
an argument.

Cheers,
Chris
--
http://rebertia.com