combinations

from itertools import combinations 
import numpy as np  
def comb(l, r): 
  
    # returns a list of all subsets of ur list 'l',  of length r 
    
    return list(combinations(l, r)) 
    print(combinations(l, r))
    
l = [1,2,3,4] #n=4
r = 2 . #k=2
comb(l, r)

#print("total number of combinations =",len(comb(l, r))) . #for number of combinations --> nCk