What are nonlocal variables in Python?

Can you explain what nonlocal variables are in Python?

Sure! Nonlocal variables are used in nested functions to refer to variables in the nearest enclosing scope that is not global.

How do I declare a nonlocal variable?

You can declare a nonlocal variable using the nonlocal keyword followed by the variable name inside a nested function.

Can you give me an example?

Of course! Here's a simple example:

x = 10

def outer_function():
    x = 20
    
    def inner_function():
        nonlocal x
        x += 5
        print(x)
    
    inner_function()
    print(x)

outer_function()

This will output 25 and then 25.

What happens if I don't use the nonlocal keyword?

If you don't use the nonlocal keyword, Python will treat the variable as a local variable within the inner function, leading to an UnboundLocalError if you try to modify it.