Bug in Python?

Question

Python

Hello, when the code is executed everything is fine

length = 100
def len():
    while True:
        if length == 0:
            break
        print(length)

len()

But when it doesn't execute, it throws the error "UnboundLocalError: local variable 'length' referenced before assignment"

length = 100
def len():
    while True:
        length -= 1
        if length == 0:
            break
        print(length)

len()

What is the problem?

Answer 1

Python uses a simple rule: if there is an assignment inside the function, then the variable is considered local. That is why the comparison uses a global variable, and in the case of a decrease by one, the interpreter considers the variable as local and does not find its initialization.