python math permutations code example

Example 1: permutations python

import itertools
print(list(itertools.permutations([1,2,3])))

Example 2: python combinations function

def combinations(iterable, r):
    pool = tuple(iterable)
    n = len(pool)
    for indices in permutations(range(n), r):
        if sorted(indices) == list(indices):
            yield tuple(pool[i] for i in indices)

Example 3: python choose function

>>> from math import comb
>>> comb(20,10)