I tried itertools.combination(iter,r), but for large numbers it gives memory error.

Copy your code here and I can have a look!

# This works for me:

import random, itertools

a = [random.randint(1, 200) for k in range(40)]

subsets = itertools.combinations(a, 5)

hit = 1

for s in subsets:

if sum(s) == 500:

print(f"{hit}: {s}")

hit += 1

# You have to put the proper indentation back yourself