Added factorial.py

Author: VarunS2002

factorial.py

@@ -0,0 +1,38 @@
+class Factorial:
+    @staticmethod
+    def factorial_iteration(number: int, use_while: bool = False) -> int:
+        factorial: int = 1
+        if number < 0:
+            raise ArithmeticError("Factorial of a negative number doesn't exist.")
+        elif not isinstance(number, int):
+            raise ArithmeticError("Factorial of non-integers is not supported.")
+        elif number == 0 or number == 1:
+            return factorial
+        else:
+            if use_while:
+                i: int = 1
+                while i < number + 1:
+                    factorial *= i
+                    i += 1
+            else:
+                for i in range(1, number + 1):
+                    factorial *= i
+        return factorial
+
+    @staticmethod
+    def factorial_recursion(number: int) -> int:
+        if number < 0:
+            raise ArithmeticError("Factorial of a negative number doesn't exist.")
+        elif not isinstance(number, int):
+            raise ArithmeticError("Factorial of non-integers is not supported.")
+        elif number == 0 or number == 1:
+            return 1
+        else:
+            return number * Factorial.factorial_recursion(number - 1)
+
+
+if __name__ == '__main__':
+    input_number = int(input("Enter a positive integer: "))
+    print("Using iteration (for):", Factorial.factorial_iteration(input_number))
+    print("Using iteration (while):", Factorial.factorial_iteration(input_number, use_while=True))
+    print("Using recursion:", Factorial.factorial_recursion(input_number))