gistfile1.py

#!/usr/bin/env python

import sys

words_file = "/usr/share/dict/words"
suffix = sys.argv[1]

candidates = set(w.strip()[:-len(suffix)] for w in open(words_file, 'rb') if w.strip().endswith(suffix))

words = [w.strip() for w in open(words_file, 'rb') if w.strip() in candidates]

print '\n'.join(words)