factorial.py

# Factorial of a number using memoization

fromfunctoolsimportlru_cache


@lru_cache
deffactorial(num: int) ->int:
"""
 >>> factorial(7)
 5040
 >>> factorial(-1)
 Traceback (most recent call last):
 ...
 ValueError: Number should not be negative.
 >>> [factorial(i) for i in range(10)]
 [1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
 """
ifnum<0:
raiseValueError("Number should not be negative.")

return1ifnumin (0, 1) elsenum*factorial(num-1)


if__name__=="__main__":
importdoctest

doctest.testmod()