Run multiple commands in parallel

purr.py

'''
Run multiple commands in parallel.

Run from CLI like

    $ python purr.py commands.txt

where `commands.txt` is a text file containing one command per line.
'''
import subprocess
import sys
import tempfile

commands = open(sys.argv[1])

processes = []
stored_exception = None
try:
    for cmd in commands:
        cmd = cmd.strip()
        if not cmd:
            continue

        stdout = tempfile.TemporaryFile()
        stderr = tempfile.TemporaryFile()
        p = subprocess.Popen(cmd, shell=True, stdout=stdout, stderr=stderr)
        processes.append( (p, stdout, stderr) )
except Exception as e:
    stored_exception = e
finally:
    with open('stdout.txt', 'wb') as master_stdout,\
            open('stderr.txt', 'wb') as master_stderr:
        for p, stdout, stderr in processes:
            p.wait()

            stdout.seek(0)
            master_stdout.write(stdout.read())
            stdout.close()

            stderr.seek(0)
            master_stderr.write(stderr.read())
            stderr.close()

    if stored_exception is not None:
        raise stored_exception