Python/maths/factorial_python.py at master · CarsonHam/Python · GitHub

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def factorial(input_number: int) -> int:

"""

Calculate the factorial of specified number

>>> factorial(1)

>>> factorial(6)

720

>>> factorial(0)

>>> factorial(-1)

Traceback (most recent call last):

...

ValueError: factorial() not defined for negative values

>>> factorial(0.1)

Traceback (most recent call last):

...

ValueError: factorial() only accepts integral values

"""

if input_number < 0:

raise ValueError("factorial() not defined for negative values")

if not isinstance(input_number, int):

raise ValueError("factorial() only accepts integral values")

result = 1

for i in range(1, input_number):

result = result * (i + 1)

return result

if __name__ == "__main__":

import doctest

doctest.testmod()

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