Introduction to Variable Scope in Python

In Python, a variable's scope determines where it can be accessed, and there are four main scope types: local, enclosing, global, and built‑in.

1. Local Scope

def local_scope():

x = 10

print(x)  # Output: 10

local_scope()

print(x)     # Error: NameError: name 'x' is not defined

2. Global Scope

y = 20

def global_scope():

print(y)  # Output: 20

global_scope()

print(y)     # Output: 20

3. Modifying Global Variables

z = 30

def modify_global():

global z

z = 40

print(z)  # Output: 40

modify_global()

print(z)     # Output: 40

4. Enclosing (Non‑local) Scope

def outer():

a = 50

def inner():

nonlocal a

a = 60

print(a)  # Output: 60

inner()

print(a)     # Output: 60

outer()

5. Built‑in Scope

def built_in_scope():

print(len("hello"))  # Output: 5

built_in_scope()

6. Local vs Global Name Collision

b = 70

def shadow_variable():

b = 80

print(b)  # Output: 80

shadow_variable()

print(b)     # Output: 70

7. Nested Function Local Variable

def outer_function():

c = 90

def inner_function():

c = 100

print(c)  # Output: 100

inner_function()

print(c)     # Output: 90

outer_function()

8. Using globals() Function

d = 110

def use_globals():

print(globals()['d'])  # Output: 110

use_globals()

9. Function Parameter vs Local Variable

def func_param(e):

e = 120

print(e)  # Output: 120

func_param(130)

10. Default Parameter Value with Global Variable

f = 140

def default_param(g=f):

print(g)  # Output: 140

default_param()

Understanding these scope rules helps write more efficient and error‑free Python code.