Let's try it: >>> re.compile('|'.join(open('/usr/share/dict/words').read().split()), re.I) OverflowError: regular expression code size limit exceeded

Let's try it: >>> re.compile('|'.join(open('/usr/share/dict/words').read().split()), re.I) OverflowError: regular expression code size limit exceeded For smaller dicts, it should work fine, but it evidently doesn't do so well on larger ones.