from difflib import Differ

namebase='AutoCompleteWindow'
fname = namebase + '.py'
ofile = open('diff23-'+namebase+'.txt', 'w')
# if this file is run with F5, output will be in same directory

f27 = open('f:/python/dev/py27/Lib/idlelib/' + fname).readlines()
f33 = open('f:/python/dev/py33/Lib/idlelib/' + fname).readlines()
for line in Differ().compare(f27, f33):
    print(line, end='', file=ofile)