local variable string interpolation in Python

t.py

import inspect
import re
import sys

class T(object):

    pattern = re.compile("#{(.+)}")
    currentframe = inspect.currentframe

    def __call__(self, template):
	 try:
	     frame = self.currentframe().f_back
	     context = frame.f_globals.copy()
	     context.update(frame.f_locals)
	 finally:
	     del frame

         def sub(match):
	     return str(context[match.group(1)])

         return self.pattern.sub(sub, template)

sys.modules[__name__] = T()