Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once.

http://docs.python.org/reference/expressions.html#notin

    randall@gulch:~$ python -c 'print 1 < 2 < 4'
    True
    randall@gulch:~$ python -c 'print 1 < 5 < 4'
    False

  >>> True + True
  2