Enclosing scope in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the enclosing scope in Python?

The enclosing scope is the scope of a function that surrounds another nested function. It is the middle layer between the local scope of the inner function and the global scope.

beginner

How does Python find a variable in nested functions?

Python looks for the variable first in the local scope, then in the enclosing scope (the outer function), then in the global scope, and finally in the built-in scope.

intermediate

What keyword allows a nested function to modify a variable in the enclosing scope?

The nonlocal keyword lets a nested function change a variable defined in its enclosing function's scope.

beginner

Example: What will this code print?

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

It will print 5 because the inner function accesses the variable x from the enclosing scope of outer.

intermediate

Why can't a nested function modify a variable in the enclosing scope without nonlocal?

Without nonlocal, assigning to a variable inside a nested function creates a new local variable, so the enclosing variable remains unchanged.

In Python, where does the enclosing scope refer to?

A The scope of the outer function surrounding a nested function

B The global scope of the program

C The local scope inside the nested function

D The built-in Python scope

The enclosing scope is the scope of the outer function that contains the nested function.

Which keyword allows a nested function to modify a variable in its enclosing scope?

A nonlocal

B global

C local

D enclose

The nonlocal keyword lets a nested function modify variables in the enclosing scope.

What happens if you assign a value to a variable inside a nested function without using nonlocal?

A It modifies the variable in the enclosing scope

B It creates a new local variable inside the nested function

C It causes a syntax error

D It modifies the global variable

Assigning without nonlocal creates a new local variable inside the nested function.

In the nested function, if a variable is not found locally, where does Python look next?

A Global scope

B Built-in scope

C It raises an error immediately

D Enclosing scope

Python looks in the enclosing scope after the local scope before checking global or built-in scopes.

What will this code print?

def outer():
    x = 10
    def inner():
        x = 20
        print(x)
    inner()
    print(x)
outer()

A 20 and 20

B 10 and 10

C 20 and 10

D 10 and 20

The inner function prints 20 (its local x), but the outer x remains 10.

Explain what the enclosing scope is and how Python uses it when looking up variables in nested functions.

Think about the layers Python checks for a variable name.

Describe how to modify a variable in an enclosing scope from inside a nested function and why this requires a special keyword.

Consider what happens when you assign a value inside a nested function.