Convert simple python for loops to while loops

f2w.py

"""
Super simple script to convert for loops to while loops
Usage:

$ python f2w.py
for i in [1,2,3]:
    print(i)
^D
__i = 0
while __i < len([1,2,3]):
    i = [1,2,3][__i]
    print(i)
    __i += 1
"""

import re
import textwrap
import sys
FOR_REGEX = re.compile(r'^(\s*)for\s+(\w+)\s+in\s+(\w+):(.+)',
                       flags=re.DOTALL | re.MULTILINE)

for_stmt = sys.stdin.read()
print(FOR_REGEX.sub(
  r"\1__i = 0\n\1while __i < len(\3):\n    \2 = \3[__i]\4    __i += 1",
  for_stmt
))