Python - my While loop does not detect integer in variable

Question

While writing an assignment for Python training, I encountered something strange. The code:

number = 0
while number is not int:
    try:
        number = int(input("Give a number to start counting with: "))
        break
    except ValueError:
        print('Please enter a valid number!')

print("the computer starts counting at number: ", number)

No matter what I fill in as value for number, the while loop runs. Filling in a 0 or 6 or even a letter, the while loop runs. If I add:

print(type(number))

to it, than it even says it is an integer. So why does the while loop not detect that? For now the program does what I want, but I find it strange behaviour that I don't understand.

You want not isinstance(number, int). Right now you're checking if number is the literal int. As in, the class int. And it's not - it's an instance of int, but it's not the class itself. — Green Cloak Guy
– Green Cloak Guy, Commented Feb 16, 2021 at 14:33

Leonardo Scotti · Accepted Answer · 2021-02-16 14:41:52Z

4

to check the type of number you have to do if type(number) is not int,
but to correctly build your loop you have to do like this:

while True:
    try:
        number = int(input("Give a number to start counting with: "))
        break
    except ValueError:
        print('Please enter a valid number!')

print("the computer starts counting at number: ", number)

in fact you fon't need to check number's type in order to stop the loop, the break inside the try: ... except: statement will do your work

answered Feb 16, 2021 at 14:41

Leonardo Scotti

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