#!/usr/bin/env python
     # encoding: utf-8
     
     import sys
     
     def trace_lines(frame, event, arg):
         if event != 'line':
             return
         co = frame.f_code
         func_name = co.co_name
         line_no = frame.f_lineno
         filename = co.co_filename
         print '  %s line %s' % (func_name, line_no)
     
     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
         line_no = frame.f_lineno
         filename = co.co_filename
         print 'Call to %s on line %s of %s' % (func_name, line_no, filename)
         if func_name in TRACE_INTO:
             # Trace into this function
             return trace_lines
         return
     
     def c(input):
         print 'input =', input
         print 'Leaving c()'
     
     def b(arg):
         val = arg * 5
         c(val)
         print 'Leaving b()'
     
     def a():
         b(2)
         print 'Leaving a()'
         
     TRACE_INTO = ['b']
     
     sys.settrace(trace_calls)
     a()