Python lambda keyword creates an anonymous function at runtime. Anonymous function sometimes is more convenient when used with itertools or enclosed in another function.

>>> f = lambda x: x%2
>>> f(3)

1

>>> f(20)

0

>>> def f(x): return x%2;

>>> from itertools import *
>>> data = [2,6,9,3,1,5]
>>> x = filter(lambda x: x%2, data)
>>> for i in x: print (i)

9
3
1
5