I see two potential problems with the non regex solutions. 1) Consider a line: "foo (bar)". When you split it you will only get two strings, as split by default only splits the string on white space characters. Thus "'bar' in words" will return false, even though bar is a word in that line.
2) If you have a line something like this: "foobar hello" then "'foo' in line" will return true, even though foo is not a word (it is part of a word). -- http://mail.python.org/mailman/listinfo/python-list
