How to do factorial in python

Answer 1

def factorial(n):
if n == 0:
return 1
else:
return n * factorial(n-1)

Or you can use the factorial() function from the math module

from math import factorial

Answer 2

No recursion needed:

x = 1
for i in range(1, 5):
x *= i

print(x)
#120

Answer 3

I would add to the answer above memoization by adding an array that store factorials already found.