PyPart4/factorial.py at master · keerthiballa/PyPart4 · GitHub

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"""
Exercise 5

Factorials are used to count permutations.

Create a program called factorial.py.

Requirements

Given a number (x), determine the value of x!
Use recursion
x		result
0!		1
1!	1 * 1	1
2!	2 * 1	2
3!	3 * 2 * 1	6
4!	4 * 3 * 2 * 1	24
5!	5 * 3 * 2 * 1	120
...	...	...
Constraints

n >= 0 n < 995

Answer below:
"""


def factorial(n):
    if n > 1:
        return (factorial(n - 1) * n)
    elif n == 0 or n==1:
        return 1
    return (factorial(n))


n = int(input("Provide a number between 0 (included) and 995: "))
if n >= 0 and n < 995:
    print('factorial of',n, 'is',factorial(n))
else:
    print("You need to provide a valid input to run the function")