[Tutor] Newbie Wondering About Threads

[Damon Timm]

Hi Everyone - I am a complete and utter Python newbie (as of today,
honestly) -- am interested in expanding my programming horizons beyond
bash scripting and thought Python would be a nice match for me.

To start, I thought I may try re-writing some of my bash scripts in
Python as a learning tool for me ... and the first one I wanted to
talkle was a script that converts .flac audio files into .mp3 files
... basic idea is I supply a sourceDirectory and targetDirectory and
then recursively convert the source file tree into an identical target
file tree filled with mp3 files.

I'm sure this has been done before (by those much wiser than me) but I
figured I can learn something as I go ... for what I've accomplished
so far, it seems pretty ugly!  But I'm learning ...

Anyhow, I think I got the basics down but I had a thought: can I
thread this program to utilize all of my cores?  And if so, how?

Right now, the lame audio encoder is only hitting one core ... I could
do all this faster if I could pass a variable that says: open 2 or 4
threads instead.

Here is what I've been working on so far -- would appreciate any
insight you may have.

Thanks,
Damon

#!/usr/bin/env python

import os
import sys
import fnmatch
from os import system

fileList = []
rootDir = sys.argv[1]
targetDir = sys.argv[2]

def shell_quote(s):
    """Quote and escape the given string (if necessary) for inclusion in
          a shell command"""
    return "\"%s\"" % s.replace('"', '\\"')

def _mkdir(newdir):
    """works the way a good mkdir should :)
        - already exists, silently complete
        - regular file in the way, raise an exception
        - parent directory(ies) does not exist, make them as well
        http://code.activestate.com/recipes/82465/
    """
    if os.path.isdir(newdir):
        pass
    elif os.path.isfile(newdir):
        raise OSError("a file with the same name as the desired " \
        "dir, '%s', already exists." % newdir)
    else:
        head, tail = os.path.split(newdir)
        if head and not os.path.isdir(head):
            _mkdir(head)
        #print "_mkdir %s" % repr(newdir)
        if tail:
            os.mkdir(newdir)

# get all the flac files and directory structures
for dirpath, subFolders, files in os.walk(rootDir):	
    for file in files:
        if fnmatch.fnmatch(file, '*.flac'):
            flacFileInfo =
[os.path.join(dirpath,file),dirpath+"/",file,dirpath.lstrip(rootDir)+"/"]
            fileList.append(flacFileInfo)

# create new directory structure and mp3 files
for sourceFile,dir,flacfile,strip in fileList:
    mp3File = shell_quote(targetDir + strip + flacfile.strip('.flac') + ".mp3")
    mp3FileDir = targetDir + strip
    sourceFile = shell_quote(sourceFile)

    _mkdir(mp3FileDir)

    flacCommand = "flac --decode --stdout --silent " + sourceFile + "
| lame -V4 --slient - " + mp3File
    system(flacCommand)