efficient machine code. Patch written by Antoine Pitrou.

Without this change, str.find() was 10% slower than str.rfind() in the worst
case.

Patch by Michael Ford.

Patch by Michael Ford.

(builting and in itertools module, i.e. map(), itertools.chain(), etc).

(builting and in itertools module, i.e. map(), itertools.chain(), etc).