Takes a URL encoded file (such as a TCP stream) and decodes it.

urldecode.py

#!/usr/bin/python

import urllib

fin = open("urlencoded.txt")
fout = open("urldecoded.txt", "wt")
for line in fin:
    fout.write(urllib.unquote(line))
fin.close()
fout.close()

Lots of examples on how to do this with strings. I couldn't find a single one that performed the action on an entire file though.