remove duplicated factorial function

Author: poyea

maths/factorial_iterative.py

@@ -1,8 +1,11 @@
-# factorial of a positive integer -- https://en.wikipedia.org/wiki/Factorial
+"""Factorial of a positive integer -- https://en.wikipedia.org/wiki/Factorial
+"""
 
 
-def factorial(n: int) -> int:
+def factorial(input_number: int) -> int:
     """
+    Calculate the factorial of specified number (n!).
+
     >>> import math
     >>> all(factorial(i) == math.factorial(i) for i in range(20))
     True
@@ -14,17 +17,27 @@ def factorial(n: int) -> int:
     Traceback (most recent call last):
         ...
     ValueError: factorial() not defined for negative values
+    >>> factorial(1)
+    1
+    >>> factorial(6)
+    720
+    >>> factorial(0)
+    1
     """
-    if n != int(n):
+    if input_number != int(input_number):
         raise ValueError("factorial() only accepts integral values")
-    if n < 0:
+    if input_number < 0:
         raise ValueError("factorial() not defined for negative values")
     value = 1
-    for i in range(1, n + 1):
+    for i in range(1, input_number + 1):
         value *= i
     return value
 
 
 if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
     n = int(input("Enter a positive integer: ").strip() or 0)
     print(f"factorial{n} is {factorial(n)}")