Python Variable Scope

1. Local Scope

def show_value():
    x = 10  # Local variable
    print(x)

show_value()
# print(x)  # NameError: x is not defined

Local variables exist only within the function where they are declared.

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2. Global Scope

x = 20  # Global variable

def display():
    print(x)

display()
print(x)

Global variables are accessible throughout the module.

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3. Local vs Global Variable Conflict

value = 50

def update():
    value = 10  # Local variable shadows global
    print("Inside function:", value)

update()
print("Outside function:", value)

Local variables override global variables within function scope.

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4. Using the global Keyword

count = 0

def increment():
    global count
    count += 1

increment()
print(count)  # Output: 1

The global keyword allows modification of global variables inside functions.

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5. Enclosing Scope (Nested Functions)

def outer():
    message = "Hello"

    def inner():
        print(message)  # Accessing enclosing variable

    inner()

outer()

Nested functions can access variables from their enclosing scope.

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6. Using the nonlocal Keyword

def outer():
    count = 0

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

    inner()
    inner()

outer()

nonlocal allows modification of variables from the enclosing (but not global) scope.

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7. LEGB Rule (Scope Resolution Order)

x = "Global"

def outer():
    x = "Enclosing"

    def inner():
        x = "Local"
        print(x)

    inner()

outer()

Python resolves variables using the LEGB rule:

• Local

• Enclosing

• Global

• Built-in

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8. Built-in Scope

print(len([1, 2, 3]))  # Built-in function

Built-in functions and exceptions reside in the built-in scope.

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9. Scope Inside Loops

for i in range(3):
    loop_var = i

print(loop_var)  # Accessible outside loop

Unlike some languages, Python loop variables are not block-scoped.

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10. Practical Example of Scope Management

total = 100

def calculate():
    total = 50

    def adjust():
        nonlocal total
        total += 10

    adjust()
    return total

print(calculate())  # Output: 60
print(total)        # Output: 100

Demonstrates coordinated use of local, enclosing, and global scopes.

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