Gaspavar's calculator

def addition():
    return x + y


def subtraction():
    return x - y


def multiplication():
    return x * y


def division():
    return x / y


print("""Welcome to Gaspavar's calculator!""")
while True:
    operation = str(input("Choose an operation: "))
    if operation.lower() != "addition" and operation.lower() != "subtraction" and operation.lower() != "multiplication" and operation.lower() != "division":
        print("Invalid value, please try again.")
    else:
        break
while True:
    try:
        x = float(input("Choose your first number: "))
        y = float(input("Choose your second number "))
    except ValueError:
        print("You can enter only numbers, please try again")
    else:
        break

if operation.lower() == "addition":
    print("Your result is " + str(addition()))
elif operation.lower() == "subtraction":
    print("Your result is " + str(subtraction()))
elif operation.lower() == "multiplication":
    print("Your result is " + str(multiplication()))
elif operation.lower() == "division":
    print("Your result is " + str(division()))