Python cycle(iterable) iterates through the iterable over and over again till break stops the loop.

>>> from itertools import *
>>> x = cycle('01')
>>> j = 1;
>>> for i in x:
... print(i,j)
... j += 1
... if (j == 7):
... break
...

0 1
1 2
0 3
1 4
0 5
1 6