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Python nonlocal Keyword

By IncludeHelp Last updated : December 07, 2024

Description and Usage

The nonlocal is a keyword (case-sensitive) in python, it is used when we work with the nested functions and we need to use a function which is declared in outer function, if we do the same, a variable will be created as local and we then we will not be able to work with a variable in inner function which is declared in outer function.

In such a case, we can define the variable (which is declared in outer function) as a nonlocal variable in inner function using nonlocal keyword.

Syntax

Syntax of nonlocal keyword:

nonlocal variable_name

Sample Input/Output

def outerfunc():
  a = 10    
  def innerfunc():
    # nonlocal binding
    nonlocal a
    a = 100
        
  # calling inner function
  innerfunc()
  # printing the value of a
  print("a : ", a)

Output:
a : 100

Example 1

Define two variables in outer function and make one variable as nonlocal in inner function.

# python code to demonstrate an example 
# of nonlocal keyword 

# nested functions
def outerfunc():
    a = 10
    b = 20
    
    def innerfunc():
    # nonlocal binding
    nonlocal a
    a = 100 # will update
    b = 200 # will not update, 
        # it will be considered as a local variable
    
    # calling inner function
    innerfunc()
    # printing the value of a and b
    print("a : ", a)
    print("b : ", b)
    
# main code
# calling the function i.e. outerfunc()
outerfunc()

Output

a :  100
b :  20

As you see in the output, a and b are the variables of outerfunc() and in the innerfunc() we are binding variable a as local, thus a will not be local here but, b will be considered as local variable for innerfunc() and if we change the value of b that will be considered a new assigned for local variable(for innerfunc()) b.

Example 2

def outer_function():
    count = 0  # Variable in the enclosing scope

    def inner_function():
        nonlocal count  # Declare 'count' as nonlocal
        count += 1  # Modify the enclosing variable
        print("Inner count:", count)

    inner_function()
    inner_function()
    print("Outer count:", count)

outer_function()

Output

Inner count: 1
Inner count: 2
Outer count: 2