Issue #21136: Avoid unnecessary normalization in Fractions resulting from power and other operations.

character for the "end" parameter

factorize the code

character for the "end" parameter

__file__.

This causes _frozen_importlib to no longer have __file__ set as well
as any frozen module imported using imp.init_frozen() (which is
deprecated).

reverse iteration using reversed().

Based on patch by Nikolaus Rath.

Based on patch by Nikolaus Rath.