added test code

calculator.py

@@ -0,0 +1,36 @@
+def add(x, y):
+    return x + y
+
+def subtract(x, y):
+    return x - y
+
+def multiply(x, y):
+    return x * y
+
+def divide(x, y):
+    if y == 0:
+        return "Cannot divide by zero!"
+    return x / y
+
+if __name__ == "__main__":
+    print("Select operation:")
+    print("1.Add")
+    print("2.Subtract")
+    print("3.Multiply")
+    print("4.Divide")
+
+    choice = input("Enter choice(1/2/3/4): ")
+
+    num1 = float(input("Enter first number: "))
+    num2 = float(input("Enter second number: "))
+
+    if choice == '1':
+        print(f"The result is: {add(num1, num2)}")
+    elif choice == '2':
+        print(f"The result is: {subtract(num1, num2)}")
+    elif choice == '3':
+        print(f"The result is: {multiply(num1, num2)}")
+    elif choice == '4':
+        print(f"The result is: {divide(num1, num2)}")
+    else:
+        print("Invalid input")