In Python, the nonlocal keyword is used to declare a variable as nonlocal, which means it is a variable that is defined in the nearest enclosing scope that is not the global scope.
When a variable is defined inside a nested function, it is considered local to that function and cannot be accessed from the outer function. However, by using the nonlocal keyword, we can access and modify the variable from the outer function. Here's an example:
def outer_function(): x = 1 def inner_function(): nonlocal x x += 1 print(x) inner_function() print(x)outer_function() |
In this example, we define the outer_function that defines a local variable x with a value of 1. Inside the outer_function, we define the inner_function that uses the nonlocal keyword to declare x as nonlocal, meaning it can be accessed and modified from the outer_function. We then modify x by adding 1 to it and print the value of x from both the inner_function and the outer_function.
When we call the outer_function, it prints 2 from the inner_function and then 2 again from the outer_function.
The use of the nonlocal keyword can be helpful in certain situations where we need to modify a variable in a nested function and have those changes reflected in the outer function. However, it should be used with caution as it can make the code more difficult to read and maintain. It's generally considered best practice to avoid using nonlocal variables and instead use function arguments and return values to communicate between nested functions.