scope
Scope defines where in your program a name (like a variable or function) can be accessed.

LEGB Rule
Python uses lexical scoping with the LEGB rule. The letters in the acronym LEGB stand for Local, Enclosing, Global, and Built-in scopes. This summarizes not only the Python scope hierarchy but also the sequence of steps that Python follows when resolving names in a program:

Local (L)
Names defined inside the current function.

def my_func():
    x = 1  # Local scope
    print(x)
Enclosing (E)
Names in any enclosing functions, from inner to outer.

def outer():
    x = 1
    def inner():
        print(x)  # Can access enclosing scope
    inner()
Global (G)
Names defined at the module level.

x = 1  # Global scope
def my_func():
    print(x)  # Accesses global x
Built-In (B)
Names preassigned in Python’s built-in namespace, such as common functions and data types.

def my_func():
    items = [1, 2, 3]
    length = len(items)  # 'len' is from built-in scope
    return str(length)   # 'str' is from built-in scope
Key Points
Python creates a new scope when defining a function or class.
The global keyword lets you modify global variables from within functions.
The nonlocal keyword lets you modify variables in an enclosing (but not global) scope.
List comprehensions create their own scope for the iterator variable.