PYTHON - SCOPE

 Python Scope

In Python, "scope" refers to the region or context in which a variable is defined and can be accessed. Python has different levels of scope, including global scope and local scope, and the scope of a variable determines where it can be used or accessed in your code. Understanding scope is crucial for writing clean, maintainable, and bug-free Python programs. Here, I'll explain in detail about Python scope with sample code.

1. Local Scope:

Variables defined within a function have local scope. They are only accessible within that function.
A new local scope is created every time a function is called, and it is destroyed when the function exits.

def my_function():
    local_variable = 42
    print(local_variable)

my_function()  # Calls the function
print(local_variable)  # Raises a NameError because local_variable is not defined here

2. Enclosing (Non-Local) Scope:

In nested functions, variables can be in an "enclosing" scope, also known as a "non-local" scope.
Variables in the enclosing scope are not global but are accessible within the nested functions.

def outer_function():
    outer_variable = 10

    def inner_function():
        print(outer_variable)  # Accesses the outer_variable from the enclosing scope

    inner_function()

outer_function()

3. Global Scope:

Variables defined outside of any function have global scope. They can be accessed from any part of the program.

global_variable = 100

def my_function():
    print(global_variable)  # Accesses the global_variable

my_function()

4. Built-in Scope:

Python has a built-in scope that contains functions and objects provided by Python itself.
You can access built-in functions and objects like print(), len(), str, and int without importing them.

print(len("Hello, World!"))  # Accesses the len() function from the built-in scope

5. Modifying Variables in an Enclosing Scope:

To modify a variable in an enclosing scope from within a nested function, you can use the nonlocal keyword.

def outer_function():
    outer_variable = 10

    def inner_function():
        nonlocal outer_variable  # Use nonlocal to modify outer_variable
        outer_variable += 5

    inner_function()
    print(outer_variable)  # Prints 15

outer_function()

6. Global Variables:

You can declare a variable as global inside a function using the global keyword.
This allows you to modify the global variable within the function.

global_variable = 100

def modify_global():
    global global_variable  # Declare global_variable as global
    global_variable += 10

modify_global()
print(global_variable)  # Prints 110

Scope determines where a variable is visible and accessible. Python follows the LEGB (Local, Enclosing, Global, Built-in) rule for variable name resolution, which means it first looks for a variable in the local scope, then in any enclosing scopes, then in the global scope, and finally in the built-in scope.