factorial.py

"""
Factorial of a positive integer -- https://en.wikipedia.org/wiki/Factorial
"""


deffactorial(number: int) ->int:
"""
 Calculate the factorial of specified number (n!).

 >>> import math
 >>> all(factorial(i) == math.factorial(i) for i in range(20))
 True
 >>> factorial(0.1)
 Traceback (most recent call last):
 ...
 ValueError: factorial() only accepts integral values
 >>> factorial(-1)
 Traceback (most recent call last):
 ...
 ValueError: factorial() not defined for negative values
 >>> factorial(1)
 1
 >>> factorial(6)
 720
 >>> factorial(0)
 1
 """
ifnumber!=int(number):
raiseValueError("factorial() only accepts integral values")
ifnumber<0:
raiseValueError("factorial() not defined for negative values")
value=1
foriinrange(1, number+1):
value*=i
returnvalue


deffactorial_recursive(n: int) ->int:
"""
 Calculate the factorial of a positive integer
 https://en.wikipedia.org/wiki/Factorial

 >>> import math
 >>> all(factorial(i) == math.factorial(i) for i in range(20))
 True
 >>> factorial(0.1)
 Traceback (most recent call last):
 ...
 ValueError: factorial() only accepts integral values
 >>> factorial(-1)
 Traceback (most recent call last):
 ...
 ValueError: factorial() not defined for negative values
 """
ifnotisinstance(n, int):
raiseValueError("factorial() only accepts integral values")
ifn<0:
raiseValueError("factorial() not defined for negative values")
return1ifnin {0, 1} elsen*factorial(n-1)


if__name__=="__main__":
importdoctest

doctest.testmod()

n=int(input("Enter a positive integer: ").strip() or0)
print(f"factorial{n} is {factorial(n)}")