simple python closure example

Original taken without permission from ScratchPad.

1>>> def counter(start=0, step=1):
2  ... x = [start]
3  ... def _inc():
4  ... x[0] += step
5  ... return x[0]
6  ... return _inc
7  ...
8  >>> c = counter()
9  >>> c()
10  1
11  >>> c()
12  2
13  >>> c()
14  3