Calcular el factorial de un número

factorial_basico.py

#! /usr/bin/env python
# -*- coding: UTF-8 -*-


n = int(
    raw_input('ingrese un numero: ')
)
m = 1

for i in range(n):
    m *= i + 1

print m

factorial_funcion.py

#! /usr/bin/env python
# -*- coding: UTF-8 -*-


def factorial(n):
    m = 1

    for i in range(n):
        m *= i + 1

    return m

n = int(
    raw_input('ingrese un numero: ')
)
print factorial(n)

factorial_profesional.py

#! /usr/bin/env python3
# -*- coding: UTF-8 -*-

from functools import reduce


def factorial(n):
    try:
        if n < 0:
            raise ValueError(
                'n has to be a positive integer')

        return reduce(lambda a, b: a*b, range(1, n+1), 1)

    except TypeError as te:
        if not isinstance(n, int):
            raise TypeError('n must be an integer') from te
        else:
            raise

if __name__ == '__main__':
    n = int(
        input('ingrese un numero: ')
    )
    print(
        factorial(n)
    )