Can't write to a directory made w/ os.makedirs

[David Goldsmith]

On Jan 2, 6:09 am, Dave Angel <d... at davea.name> wrote:
> On 01/01/2012 10:14 PM, David Goldsmith wrote:
>
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> > On Jan 1, 7:05 am, Tim Golden<m... at timgolden.me.uk>  wrote:
> >> On 01/01/2012 12:05, David Goldsmith wrote:
> >>   >>  ie can the Python process creating the directories,
>
> >>   >  Yes.
>
> >>   >>  and a subprocess called from it create a simple file?
>
> >>   >  No.
>
> >>   >>  Depending on where you are in the filesystem, it may indeed
> >>   >>  be necessary to be running as administrator. But don't try
> >>   >>  to crack every security nut with an elevated sledgehammer.
>
> >>   >  If you mean running as admin., those were my sentiments exactly.  So,
> >>   >  there isn't something specific I should be doing to assure that my
> >>   >  subproceses can write to directories?
>
> >> In the general case, no. By default, a subprocess will have
> >> the same security context as its parent. The exception is
> >> where the parent (the Python processing invoking subprocess.call
> >> in this example) is already impersonating a different user;
> >> in that case, the subprocess will inherit its grandparent's
> >> context.
>
> >> But unless you're doing something very deliberate here then
> >> I doubt if that's biting you.
>
> >> Can I ask: are you absolutely certain that the processes
> >> you're calling are doing what you think they are and failing
> >> where you think they're failing?
>
> >> TJG
> > I'm a mathematician: the only thing I'm absolutely certain of is
> > nothing.
>
> > Here's my script, in case that helps:
>
> > import os
> > import sys
> > import stat
> > import os.path as op
> > import subprocess as sub
> > from os import remove
> > from os import listdir as ls
> > from os import makedirs as mkdir
>
> > def doFlac2Mp3(arg, d, fl):
> >      if '.flac' in [f[-5:] for f in fl]:
> >          newD = d.replace('FLACS', 'MP3s')
> >          mkdir(newD)
> >          for f in fl:
> >              if f[-5:]=='.flac':
> >                  root = f.replace('.flac', '')
> >                  cmd = ['"C:\\Program Files (x86)\\aTunes\\win_tools\
> > \flac.exe" -d ' +
> >                         '--output-prefix=' + newD + '\\', f]
> >                  res = sub.call(cmd)#, env={'PATH': os.defpath})
> >                  if not res:
> >                      cmd = ['"C:\\Program Files (x86)\\aTunes\\win_tools
> > \\lame.exe" -h',
> >                              newD + root + '.wav',  newD + root +
> > '.mp3']
> >                      res = sub.call(cmd)#, env={'PATH': os.defpath})
> >                      if not res:
> >                          rf = newD + root + '.wav'
> >                          remove(rf)
>
> > top=sys.argv[1]
> > op.walk(top, doFlac2Mp3, None)
>
> The line cmd= is bogus.  You're trying to run a program with a -h after
> the filename.  The reason you're passing a list to sub.call is to
> separate the parameters from the program name, not to mention with
> quotes in its name.  So the -h has to be  a separate list item.
> (Although Windows will probably handle it correctly if you combine the
> -h with the FOLLOWING argument, it's still bad practice]
>
> cmd = [ "c:\\program files .... \\lame.exe", "-h", newD + root + ....."
>
> --
>
> DaveA

Thanks, this is the kind of feedback I was hoping for--the
documentation for subprocess.call is notably "sparing" to put it
politely.  However, having not yet tried it, I'm skeptical, as what
doc there is says:

"subprocess.call(args, *, stdin=None, stdout=None, stderr=None,
shell=False)

    Run the command described by args. Wait for command to complete,
then return the returncode attribute.

    The arguments shown above are merely the most common ones,
described below in Frequently Used Arguments (hence the slightly odd
notation in the abbreviated signature). The full function signature is
the same as that of the Popen constructor - this functions passes all
supplied arguments directly through to that interface.
:
:
"class subprocess.Popen(args, bufsize=0, executable=None, stdin=None,
stdout=None, stderr=None, preexec_fn=None, close_fds=False,
shell=False, cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0)

    Arguments are:

    args should be a string, or a sequence of program arguments...On
Windows: the Popen class uses CreateProcess() to execute the child
child program, which operates on strings. If args is a sequence, it
will be converted to a string in a manner described in Converting an
argument sequence to a string on Windows."  Thus I didn't really see
the point of separating out the -h string--which tells lame to use
high quality encoding--into another sequence element, but as per your
advice, I'll try it (along with Tim's and MRAB's suggestions; I'll
report back what works).