Python Namespace and Scope

1. What is a Namespace

A namespace is a container that holds identifiers (variables, functions, objects) and maps them to their corresponding values.

a = 10

Here, a resides in a namespace and points to the value 10.

Types of namespaces:

• Built-in namespace

• Global namespace

• Local namespace

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2. Built-in Namespace

Contains built-in functions and objects provided by Python.

print(len([1, 2, 3]))
print(type(100))

These functions belong to the built-in namespace and are always available.

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3. Global Namespace

Created when a module is loaded and remains until the program terminates.

x = 50  # Global variable

def show():
    print(x)

show()

Global variables are accessible throughout the module.

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4. Local Namespace

Created inside a function and destroyed when the function exits.

def calculate():
    y = 20  # Local variable
    print(y)

calculate()
# print(y)  # NameError

Local namespace is limited to function scope.

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5. Accessing Namespace Using globals()

x = 100

print(globals()["x"])  # Output: 100

globals() returns a dictionary of all global identifiers.

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6. Accessing Namespace Using locals()

def demo():
    a = 10
    b = 20
    print(locals())

demo()

locals() returns a dictionary of local variables within a scope.

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7. LEGB Rule (Scope Resolution Order)

Python resolves variable names in the following order:

• Local

• Enclosing

• Global

• Built-in

x = "Global"

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

outer()

Output follows the closest scope: Local → Enclosing → Global → Built-in.

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8. Enclosing Namespace

Occurs in nested functions, holding variables from outer functions.

def outer():
    message = "Hello"
    def inner():
        print(message)
    inner()

outer()

Inner functions can reference enclosing variables.

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9. Modifying Enclosing Variables with nonlocal

def counter():
    value = 0
    def increment():
        nonlocal value
        value += 1
        return value
    return increment

count = counter()
print(count())
print(count())

nonlocal allows modification of variables in the enclosing namespace.

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10. Namespace Lifecycle Demonstration

x = "Global"

def test():
    x = "Local"
    print("Inside:", x)

test()
print("Outside:", x)

Shows that separate namespaces prevent conflicts between global and local variables.

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Summary

Concept	Purpose
Namespace	Container mapping names to objects
Scope	Region where a variable is accessible
LEGB Rule	Determines variable resolution order
globals()	Access global variables
locals()	Access local variables

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