python counter with closure

Question

I\'m trying to build a counter in python with the property of closure. The code in the following works:

def generate_counter():
    CNT = [0]
    def add_one         


        

Answer 1

It doesn't have to be a list, it just has to be an mutable object which you mutate, not reassign.

From the docs:

If a variable is assigned a value anywhere within the function’s body, it’s assumed to be a local unless explicitly declared as global.

Thus, in your second example, x is considered local (to the inner function), and, after your first assignment, you're shadowing the outer 'x'.

On the other hand, in the first example (since you don't assign a value to CNT) it operates on the CNT defined in the outer function.