In [1]:

    

# Solution 1
from scipy.misc import comb
print comb(40,20, exact=True)


    

    




137846528820

In [2]:

    

# A native implementation of N choose K from StackOverflow
from operator import mul    # or mul=lambda x,y:x*y
from fractions import Fraction

def nCk(n,k): 
  return int( reduce(mul, (Fraction(n-i, i+1) for i in range(k)), 1) )

nCk(40,20)


    

    
Out[2]:





137846528820

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