Find old-style (pre django 1.5) {% url %} tags

ext.py

"""Given a list of files, print out the file extensions"""
import sys

for l in sys.stdin:
    print l[:-1].rsplit('.')[-1]

Find old-style (pre django 1.5) {% url %} tags

Find: "\{\%\W*url +([-_a-zA-Z:0-9]+)\W"
Replace: "{% url '\1' "

(Don't forget you'll also need 
{% load url from future %} if on 1.5.

----
If you'd like to whittle the tree down to just files that could possibly have old-style urls:

Find files in tree that have the {% url tag in them at all:

# find filenames with "{% url " or "{%url " (since both work).
$ grep --binary-file=without-match --ignore-case --recursive --files-with-matches --extended-regexp '\{\% ?url' * > file-list

# strip that list down to just extensions:
$ python ../../ext.py < file-list > matching-extensions 
# find the extensions that need to be searched/replaced:
$ (sort --ignore-case matching-extensions | uniq ) < matching-extensions