nonlocal

In Python, the nonlocal keyword lets you declare a variable in a nested function as not local to that function. It allows you to modify variables defined in the enclosing scope from within an inner function.

Python nonlocal Keyword Examples

Here’s a quick example to illustrate how the nonlocal keyword works:

Python 
>>> def outer_function():
...     number = 10
...     def inner_function():
...         nonlocal number
...         number = 42
...         print("Inner:", number)
...     inner_function()
...     print("Outer:", number)
...

>>> outer_function()
Inner: 42
Outer: 42

In this example, outer_function() defines a variable number and a nested inner_function(). By using the nonlocal keyword inside inner_function(), you tell Python that number refers to the variable in the enclosing scope provided by outer_function(). When inner_function() is called, it changes number to 42, which is then reflected when outer_function() prints number.

Python nonlocal Keyword Use Cases

  • Modifying variables in enclosing scopes, particularly useful in closures
  • Maintaining state in nested functions
  • Avoiding the use of global variables for encapsulation and scope management
Python Inner Functions

Tutorial

Python Inner Functions: What Are They Good For?

Learn how to create inner functions in Python to access nonlocal names, build stateful closures, and create decorators.

intermediate python

For additional information on related topics, take a look at the following resources:

By Leodanis Pozo Ramos • Updated Jan. 6, 2025 • Reviewed by Dan Bader
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