How to get all combinations of length n in python

Question

I was wondering if there is any way of getting all combinations of length n from a list of numbers.

For example, if my list is [1, 2, 3, 4], and I want to output (if I chose n = 3)

[1, 2, 3] [1, 2, 4] [1, 3, 4] [2, 3, 4] 

the other permutations like [2,1,3] are of no use to me.

Answer 1

itertools can do this:

import itertools  for comb in itertools.combinations([1, 2, 3, 4], 3):     print(comb) 

Outputs:

(1, 2, 3) (1, 2, 4) (1, 3, 4) (2, 3, 4) 

Answer 2

Adding the recursive function:

def combinations(array, tuple_length, prev_array=[]):     if len(prev_array) == tuple_length:         return [prev_array]     combs = []     for i, val in enumerate(array):         prev_array_extended = prev_array.copy()         prev_array_extended.append(val)         combs += combinations(array[i+1:], tuple_length, prev_array_extended)     return combs  combinations([1, 2, 3, 4], 3) 

Outputs:

[[1, 2, 3],  [1, 2, 4],  [1, 3, 4],  [2, 3, 4]]