Cartesian product of 2 ranges in python

Question

Do you know how to loop over cartesian products of two ranges in python, such as:

for i,j in cartesian(100,200):
 print i, j

0,0
0,1
.
.
.
123,197
.
.
99,199

May this help? http://stackoverflow.com/questions/533905/get-the-cartesian-product-of-a-series-of-lists-in-python — Pavel, Sep 12 '13 at 12:35

score 13 · Answer 1 · answered Sep 12 '13 at 12:44

The product function will work:

from itertools import product
for j in product(range(100), range(200)):
  print j

Equivalent to nested for-loops in a generator expression. For example, product(A, B) returns the same as ((x,y) for x in A for y in B).

Wolph · Answer 2 · 2013-09-12T13:28:05.427

4

Maybe I'm missing something, but isn't it as simple as this:

for i in range(100):
    for j in range(200):
        print i, j

Slightly more optimized version:

inner_range = range(200)
for i in range(100):
    for j in inner_range:
        print i, j

edited Sep 12 '13 at 13:28

answered Sep 12 '13 at 12:41

Wolph

which is faster, yours or JLLagrange's? – alwbtc Sep 12 '13 at 12:52
Most likely this version since it's the simplest most pure Python solution you can get. Using the product method gives you an extra wrapper so inherently a bit of speed loss but it might omit generating the second range a hundred times. Having that said, any difference is bound to be negligible anyhow. – Wolph Sep 12 '13 at 13:22
Why didn't you use `outer_range = range(100)`? – alwbtc Sep 12 '13 at 18:55
1

The outer range is only used once, the inner range 100 times since it's within the for loop. For cleanless you could but it shouldn't make any difference. – Wolph Sep 12 '13 at 21:46
product seems to be a lot faster when iterating over data like numpy arrays. – Hyperplane Feb 15 '19 at 15:45

2 Answers2