Can somebody please explain the below output?

Question

def closure_add():
    x = 3
    def adder():
        nonlocal x
        x+=1
        return x
    return adder
a = closure_add()
b = closure_add()
print(a())
print(b())
print(b())
print(b())

The output is:

4
4
5
6

If variable 'b' which holds the function 'adder' remembers the scope of variable (x=3), shouldn't the output be '4' no matter how many times you call it.

Answer 1

Links below should provide more info:

• Python closures
• Python nonlocal statement

What this boils down to in the end in your example:

1. You instantiate two separate function objects in variables a and b
2. You invoke a once, it increases the value once
3. You invoke b three times which increases the value three times

Since the value that gets increased in the closure is defined in the method that increases it as nonlocal, the value is stored after each change that is done to it in the parent function, in the x variable.