[ http://www.python.org/moin/PythonSpeed ] "Starting with Py2.3, the interpreter optimizes 'while 1' to just a single jump. In contrast "while True" takes several more steps. While the latter is preferred for clarity, time-critical code should use the first form."
Out of pure curiousity, Why wasn't 'While True' optimized also? -- http://mail.python.org/mailman/listinfo/python-list
