#!/usr/bin/env python
     # encoding: utf-8
     
     import sys
     
     def trace_calls(frame, event, arg):
         if event != 'call':
             return
         co = frame.f_code
         func_name = co.co_name
         if func_name == 'write':
             # Ignore write() calls from print statements
             return
         func_line_no = frame.f_lineno
         func_filename = co.co_filename
         caller = frame.f_back
         caller_line_no = caller.f_lineno
         caller_filename = caller.f_code.co_filename
         print 'Call to %s on line %s of %s from line %s of %s' % \
             (func_name, func_line_no, func_filename,
              caller_line_no, caller_filename)
         return
     
     def b():
         print 'in b()'
     
     def a():
         print 'in a()'
         b()
     
     sys.settrace(trace_calls)
     a()