finding a sum of X numbers within a list (Python)

Question

i'm trying to find a combination for a sum inside a list of integers.

the amount of numbers that contain the sum is limited by a variable, so for example in the list -

[5,2,3,9,1], i would like to find the sum of 10, with only 2 numbers.

so that the program would print out [9,1].

I'm new to python, is there an easy way of doing it?

thank you.

Answer 1

from itertools import combinations

l = [5,2,3,9,1]

for var in combinations(l, 2):
    if var[0] + var[1] == 10:
        print var[0], var[1]

Combinations create all possible combinations of tuples from an iterable object (an object you can loop over). Let me demonstrate:

>>> [var for var in combinations([1,2,3,4,5], 2)]
[(1, 2), (1, 3), (1, 4), (1, 5), (2, 3), (2, 4), (2, 5), (3, 4), (3, 5), (4, 5)]
>>> [var for var in combinations([1,2,3,4,5], 3)]
[(1, 2, 3), (1, 2, 4), (1, 2, 5), (1, 3, 4), (1, 3, 5), (1, 4, 5), (2, 3, 4), (2, 3, 5), (2, 4, 5), (3, 4, 5)]