# foo.py

x = [0]

import foo
from foo import x as x2

if __name__ == "foo":
  print x, x2, foo.x
  x[0] = 1
  print x, x2, foo.x
  x2[0] = 2
  print x, x2, foo.x
  foo.x[0] = 3
  print x, x2, foo.x
  x = 1
  print x, x2, foo.x
  x2 = 2
  print x, x2, foo.x
  foo.x = 3
  print x, x2, foo.x

Загадка знатокам питона: что будет выведено, если запустить python foo.py ?