Printing combinations of two lists in Python

Question

What I'm trying to print is the following, using 2 variables in each string for simplicity. I think something's wrong using the loops, i'm kinda new to Python. Thanks in advance!
com0 <-(a) with (1,)
com1 <-(a) with (2,)
com2 <-(a) with (1, 2)
com3 <-(b) with (1,)
com4 <-(b) with (2,)
com5 <-(b) with (1, 2)
com6 <-(a,b) with (1,)
com7 <-(a,b) with (2,)
com8 <-(a,b) with (1, 2)

This is what I've tried:
import itertools

i = 0 #v1
j = 0 #v2

v1 = [1, 2]
v2 = ["a","b"]

while j < 2**len(v2):

for K in range(0, len(v2)+1):

while i < 2**len(v1):

for L in range(0, len(v1)+1):

for subset2 in itertools.combinations(v1, L):

for subset1 in itertools.combinations(v2, K):

print("com{0} <-{1} with {2}".format(i,subset1,subset2))

i+=1
                        j+=1

Prem Anand · Answer

You dont need these many loops for this. Just use combinations and product from itertoools

>>> from itertools import combinations, product
>>> 
>>> v1 = [1, 2]
>>> v2 = ["a","b"]
>>> 
>>> all_v1 = [e for i in range(len(v1)) for e in combinations(v1,i+1)]
>>> all_v2 = [e for i in range(len(v1)) for e in combinations(v2,i+1)]
>>> 
>>> for i, (x,y) in enumerate(product(all_v2, all_v1)):
...     print (f'com{i} <-{x} with {y}')
... 
com0 <-('a',) with (1,)
com1 <-('a',) with (2,)
com2 <-('a',) with (1, 2)
com3 <-('b',) with (1,)
com4 <-('b',) with (2,)
com5 <-('b',) with (1, 2)
com6 <-('a', 'b') with (1,)
com7 <-('a', 'b') with (2,)
com8 <-('a', 'b') with (1, 2)

Answered by Prem Anand on January 3, 2022

Bram Dekker · Answer

The product() from itertools results in the Cartesian product of the two lists. By using this function you avoid all the loops:
import itertools

v1 = [1, 2]
v2 = ["a","b"]
combinations = list(itertools.product(v1, v2))
>> [(1, "a"), (1, "b"), (2, "a"), (2, "b")]

Printing combinations of two lists in Python

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