Nonlocal keyword in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the nonlocal keyword do in Python?

It allows a function to modify a variable defined in its nearest enclosing scope that is not global.

intermediate

Why can't you use global to modify variables in an enclosing function?

global only affects variables at the module (global) level, not variables inside enclosing functions. nonlocal is needed for enclosing function variables.

beginner

Given this code snippet, what will be printed?

def outer():
    x = 5
    def inner():
        nonlocal x
        x = 10
    inner()
    print(x)
outer()

It will print 10 because inner() changes x in the enclosing outer() function using nonlocal.

intermediate

What error occurs if you use nonlocal on a variable that doesn't exist in any enclosing scope?

Python raises a SyntaxError because nonlocal requires the variable to exist in an enclosing function scope.

beginner

Can nonlocal be used to modify global variables?

No. nonlocal only works with variables in enclosing functions. Use global to modify global variables.

What does the nonlocal keyword allow you to do?

A Modify a global variable

B Modify a variable in the nearest enclosing function scope

C Create a new local variable

D Delete a variable

nonlocal lets you change variables in the nearest enclosing function, not global or local variables.

What happens if you use nonlocal on a variable not found in any enclosing scope?

A Python raises a SyntaxError

B The variable is created locally

C The variable is created globally

D Nothing happens

Python requires the variable to exist in an enclosing function scope for nonlocal. Otherwise, it raises a SyntaxError.

Which keyword should you use to modify a global variable inside a function?

A enclosing

B local

C nonlocal

D global

global is used to modify variables at the module (global) level.

In this code, what will be printed?

def outer():
    x = 1
    def inner():
        x = 2
    inner()
    print(x)
outer()

A 2

B Error

C 1

D None

inner() creates a new local x, so outer()'s x remains 1.

Which of these is true about nonlocal?

A It can only be used inside nested functions

B It can be used anywhere in the program

C It creates a new global variable

D It deletes variables

nonlocal is only valid inside nested functions to access variables in the outer function.

Explain how the nonlocal keyword works with an example.

Think about nested functions and changing variables outside the inner function.

What is the difference between nonlocal and global keywords?

Consider where the variable lives: inside a function or at the module level.