How to create in a 2-dimentionals array all combinations from 2 different array

Question

I have to create a multiple dimensional list that looks like this :

[[[1,R],[1,R]],[[1,B],[1,B]],[[2,R],[1,B]],[[2,R],[2,B]]]...

From two lists :

[1,2] and [R,B]

My objective is to create all the possible combinations.

I've done something that is working. with a while, but when the number of combinations is huge it takes so much time. For exemple when i have n(it is the number of color) = 5 And N = 6 --> RandomedColor= [Red,white,black,green,Yellow] and liste2 = [1,2,3,4,5,6] it will take at least 5 mins to be done.

def Create_All_list_from_n(N): #Create all possible combinations of numbers with colors. if n = 2, and N = 5 then, there will be 2**5 combinations.
    all_list_of_N = []
    while(len(all_list_of_N) != n**N):     
        current_list = []
        for i in range(1,N+1):
            current_list.append([random.choice(RandomedColors),i])
        if current_list not in all_list_of_N:
            all_list_of_N.append(current_list)
        print(all_list_of_N)
        print(len(all_list_of_N))
    return all_list_of_N

Thanks for helping !

norok2 · Accepted Answer · 2019-10-15 11:12:35Z

1

This can be implemented relatively efficiently with itertools.product().

For example:

import itertools


print(list(itertools.product([1, 2], ['R', 'B'])))
# [(1, 'R'), (1, 'B'), (2, 'R'), (2, 'B')]

and then you can use that to generate the replicas you need.

answered Oct 15, 2019 at 11:12

norok2

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Sayandip Dutta · Accepted Answer · 2019-10-15 11:16:16Z

0

You can use product and combinations_with_replacement from itertools

from itertools import product, combinations_with_replacement
x = [1,2]
y = ['R','B']
products = [list(i) for i in product(x,y)]
print([list(i) for i in combinations_with_replacement(products,2)])

Output:

[[[1, 'R'], [1, 'R']], [[1, 'R'], [1, 'B']], [[1, 'R'], [2, 'R']], [[1, 'R'], [2, 'B']], [[1, 'B'], [1, 'B']], [[1, 'B'], [2, 'R']], [[1, 'B'], [2, 'B']], [[2, 'R'], [2, 'R']], [[2, 'R'], [2, 'B']], [[2, 'B'], [2, 'B']]]

edited Oct 15, 2019 at 11:16

answered Oct 15, 2019 at 11:13

Sayandip Dutta

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1 Comment

Mathieu Over a year ago

As you can see in his example, he has the combination [1, 'R'], [1, 'R']. As per my answer, you should use combinations_with_replacement() instead of combinations().

Mathieu · Accepted Answer · 2019-10-15 11:13:36Z

0

To handle combinatory problems, itertools is very usefull. It offers all the required function to generate the combinations.

The idea is to use product and then combinations_with_replacement.

L1 = [1,2]
L2 = ["R" ,"B"]

import itertools

products = list(itertools.product(L1, L2))
combinations = list(itertools.combinations_with_replacement(products, 2))

Output:

[((1, 'R'), (1, 'R')),
 ((1, 'R'), (1, 'B')),
 ((1, 'R'), (2, 'R')),
 ((1, 'R'), (2, 'B')),
 ((1, 'B'), (1, 'B')),
 ((1, 'B'), (2, 'R')),
 ((1, 'B'), (2, 'B')),
 ((2, 'R'), (2, 'R')),
 ((2, 'R'), (2, 'B')),
 ((2, 'B'), (2, 'B'))]

answered Oct 15, 2019 at 11:13

Mathieu

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