#!/usr/bin/env python

import os, sys

where = sys.argv[1]
fromext = sys.argv[2]
if not fromext.startswith("."): fromext = "."+fromext
toext = sys.argv[3]
if not toext.startswith("."): toext = "."+toext

for (root, subdirs, names) in os.walk(where):
	for name in [x for x in names if x.endswith(fromext)]:
		newname = name[0:-len(fromext)] + toext
		print os.path.join(root, name), "->", newname
		os.rename(os.path.join(root, name), os.path.join(root, newname))