Two additional things beyond the important lesson to always time things: 1. Be careful with operator precedence. In this case, people got lucky:
not b in m has the precedence: not (b in m) 2. Python has a "not in" operator: b not in m which is the clearest and fastest way to test for non-membership in a container. Tim Delaney -- http://mail.python.org/mailman/listinfo/python-list