“nonlocal” Keyword in Python: Accessing Variables in Enclosing Scopes

Python is a powerful and versatile programming language that has gained immense popularity among developers all over the world. It has many features that make it stand out from other programming languages, making it an ideal choice for writing complex and large-scale applications. One of the most useful and powerful features of Python is its ability to access variables in enclosing scopes using the “nonlocal” keyword. In this article, we’ll explore this keyword and see how it can be used in Python programming.

What Does “nonlocal” Mean?

The “nonlocal” keyword in Python is used to access a variable in the enclosing scope, which is the scope that surrounds the current function. This is different from the “global” keyword, which is used to access a variable in the global scope.

The “nonlocal” keyword is useful when you have a nested function, which is a function that is defined inside another function, and you want to access a variable in the outer function’s scope. It allows you to modify the value of the variable in the outer function’s scope from the inner function, which would not be possible using other methods.

Example 1: Using nonlocal Keyword in a Nested Function

Let’s take a look at an example to see how the “nonlocal” keyword can be used to access a variable in the outer function’s scope:

def outer_function():
    x = "outer"

    def inner_function():
        nonlocal x
        x = "inner"

    inner_function()
    print("x =", x)

outer_function()

In this example, we have a nested function called “inner_function” that is defined inside the “outer_function”. The “outer_function” has a variable called “x” that is set to “outer” initially.

The “inner_function” uses the “nonlocal” keyword to access the variable “x” in the outer function’s scope and sets its value to “inner”. This modifies the value of the variable “x” in the outer function’s scope.

After the “inner_function” is called, we print the value of the variable “x” in the “outer_function” and we can see that its value has been changed to “inner”.

Output:

x = inner

Example 2: Using nonlocal Keyword in a Nested Function with a Loop

Now let’s take a look at another example that uses the “nonlocal” keyword in a nested function that contains a loop:

def outer_function():
    count = 0

    def inner_function():
        nonlocal count
        count += 1
        print(count)

    for i in range(3):
        inner_function()

outer_function()

In this example, we have a nested function called “inner_function” that is defined inside the “outer_function”. The “outer_function” has a variable called “count” that is set to 0 initially.

The “inner_function” uses the “nonlocal” keyword to access the variable “count” in the outer function’s scope and increments its value by 1 each time it is called. It then prints the current value of “count”.

The “outer_function” contains a loop that calls the “inner_function” three times. Each time the “inner_function” is called, it modifies the value of the variable “count” in the outer function’s scope and prints its current value.

Output:

1
2
3

Conclusion

The “nonlocal” keyword in Python is a powerful tool that allows you to access variables in enclosing scopes from nested functions. This can be extremely useful when you need to modify the value of a variable in the outer function’s scope from the inner function. By using “nonlocal”, you can avoid using global variables or complex workarounds, and write clean and efficient code.

We hope you found this article helpful in understanding the “nonlocal” keyword in Python. Happy coding!