Find all possible combinations of items in array of arrays

Question

I have an array of arrays that looks like this:

arrays = [['a', 'b'], [1, 2], ['x', 'y', 'z']]

but could also be expanded.

I need to feed these to my_function(a_or_b, one_or_two, x_y_or_x) in all of their possible combinations (a 1 x, a 2 x, a 1 y, a 1 z, ecc). Using numpy is an option.

Though it appears as a simple problem, I have no idea where to start...

Yes, I could loop like:

for array in arrays:
    for ...

and then what? Looping through the arrays means that on my second iteration arrays[0] would no longer be first and I'd mess up the order. I also would have duplicates.

How can I do this? I don't care in which order these functions are called, but I do care that they're not called twice with the same combination and that the arguments are in order.

my_function(a, 1, x)
my_function(b, 1, x)
my_function(a, 2, x)
my_function(b, 2, x)
my_function(a, 1, y)
my_function(b, 1, y)
my_function(a, 2, y)
ecc...

Try itertools.product or one of the other very useful tools in itertools — Tacratis
– Tacratis, Commented Feb 21, 2019 at 1:39

Saturnix · Accepted Answer · 2019-02-21 02:09:30Z

4

itertools.product does exactly this. It will generate all combinations from your 3 sublists. Then you can unpack them as arguments in your function:

from itertools import product

combs = product(*arrays)
for comb in combs:
    my_function(*comb)

Calls

my_function('a', 1, 'x')
my_function('a', 1, 'y')
my_function('a', 1, 'z')
my_function('a', 2, 'x')
my_function('a', 2, 'y')
my_function('a', 2, 'z')
my_function('b', 1, 'x')
my_function('b', 1, 'y')
my_function('b', 1, 'z')
my_function('b', 2, 'x')
my_function('b', 2, 'y')
my_function('b', 2, 'z')

edited Feb 21, 2019 at 2:09

Saturnix

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answered Feb 21, 2019 at 1:42

busybear

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