Create A_factorial.py

Python/A_factorial.py

@@ -0,0 +1,22 @@
+class FactorialCalculator:
+    def __init__(self, number):
+        self.number = number
+
+    def calculate(self):
+        if self.number < 0:
+            raise ValueError("Factorial is not defined for negative numbers.")
+        return self._factorial(self.number)
+
+    def _factorial(self, n):
+        if n == 0 or n == 1:
+            return 1
+        else:
+            return n * self._factorial(n - 1)
+
+try:
+    num = int(input("Enter a non-negative integer: "))
+    calculator = FactorialCalculator(num)
+    result = calculator.calculate()
+    print(f"The factorial of {num} is {result}.")
+except ValueError as e:
+    print(e)