Double Iteration in List Comprehension

doubleiter.py

>>> seq_x = [1, 2, 3, 4]
>>> seq_y = 'abc'
>>> [(x,y) for x in seq_x for y in seq_y]
1: [(1, 'a'),
 (1, 'b'),
 (1, 'c'),
 (2, 'a'),
 (2, 'b'),
 (2, 'c'),
 (3, 'a'),
 (3, 'b'),
 (3, 'c'),
 (4, 'a'),
 (4, 'b'),
 (4, 'c')]