Python interim evaluation calculator (number)

def calculator(numbers):
    if type(numbers) != "list":
        raise ValueError
    length = len(numbers)

    total = 0
    for num in numbers:
        total += num

    return length, total

# When entering a list containing numbers, 1) length of the list, 2) return the sum of the numbers
numbers = [1,2,3]
print(calculator(numbers))

# Error occurs when numbers enter str type
numbers = "1,2,3"
print(calculator(numbers))