permutations of two lists in python

Question

I have two lists like:

list1 = ['square','circle','triangle'] list2 = ['red','green'] 

How can I create all permutations of these lists, like this:

[   'squarered', 'squaregreen',   'redsquare', 'greensquare',   'circlered', 'circlegreen',   'redcircle', 'greencircle',   'trianglered', 'trianglegreen',   'redtriangle', 'greentriangle' ] 

Can I use itertools for this?

Answer 1

You want the itertools.product method, which will give you the Cartesian product of both lists.

>>> import itertools >>> a = ['foo', 'bar', 'baz'] >>> b = ['x', 'y', 'z', 'w']  >>> for r in itertools.product(a, b): print r[0] + r[1] foox fooy fooz foow barx bary barz barw bazx bazy bazz bazw 

Your example asks for the bidirectional product (that is, you want 'xfoo' as well as 'foox'). To get that, just do another product and chain the results:

>>> for r in itertools.chain(itertools.product(a, b), itertools.product(b, a)): ...   print r[0] + r[1]