new_contents: #!/usr/bin/env python
  # http://www.mojidong.com/python/2013/05/10/python-exec-eval/
  
  a = 2
  exec "a=1"
  print(a)
  
  a = 10
  b = 20
  g = {
      'a':6,
      'b':8
  }
  exec "global a; print a,b" in g
  
  a = 10
  b = 20
  c = 20
  g = {
      'a':6,
      'b': 8
  }
  l = {
      'b':9,
      'c':10
  }
  exec "global a;print a,b,c" in g,l
  
subject: add exec