Hi Terry,
> > But that's not "using your existing... functional-programming
> > thingy" mentioned above.
> >
> > mp3_files = sorted(os.path.join(mp3_subdir, x) for x in
> > filter(lambda f: f.lower().endswith(".mp3"), os.listdir(mp3_subdir)))
>
> No it's not, but that bit of code produces a list of files, including
> paths, separated by commas (all the os methods that I tried (such as
> os.list dir do).
No, it produces a `list', a Python type that's an array-like data
structure that can change length. You've been writing lists literally
with brackets in your code, e.g. Popen() is being passed one parameter
here:
subprocess.Popen(['mpg321', '-q', '-m', '-a', 'hw:0,0', 'foo.mp3'])
Python prints lists with commas between items, but a list isn't a string
and the commas are just formatting. You need to join your mp3_files
list onto the end of your hard-coded ['mpg321'...] one so Popen() sees
just one long list.
https://docs.python.org/2/tutorial/introduction.html#lists
> I suspected as much. Presumably in the shell the * is expanded before
> it is given to mpg321 (without commas) so it works.
Yes, unlike DOS, glob expansion is normally done by the shell and
programs just see literal file names to process. This aids consistency
as each program doesn't develop their own dialect, and allows
centralised improvements, e.g. bash's `**' globstar.
Historically, it was a separate program to the shell due to memory
constraints, called glob(1), but these days shells have it built in, and
larger languages provide similar logic in libraries, e.g. glob.glob().
Cheers, Ralph.
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