Python Variable Scope: Local, Global, and Nonlocal

What Is Variable Scope in Python?

Scope refers to the region of a program where a variable is recognized and can be used. In Python, there are mainly three types of variable scopes:

• Local Scope
• Global Scope
• Nonlocal Scope

1. Local Scope in Python

A variable created inside a function is called a local variable and is only accessible within that function.

Example:

def greet():
    message = "Hello from inside!"
    print(message)

greet()
# print(message)  # This would cause an error (uncomment to test)

Output:

Hello from inside!

2. Global Scope in Python

A global variable is defined outside any function and is accessible throughout the program, even inside functions (read-only by default).

Example:

name = "Alice"  # Global variable

def greet():
    print("Hello", name)

greet()

Output:

Hello Alice

Modifying Global Variables Inside Functions

To modify a global variable inside a function, use the global keyword.

count = 0

def increment():
    global count
    count += 1
    print("Count inside:", count)

increment()
print("Count outside:", count)

Output:

Count inside: 1
Count outside: 1

3. Nonlocal Scope in Python

The nonlocal keyword is used to modify a variable in the nearest enclosing scope (not global, but not local to the current function either). Commonly used in nested functions.

Example:

def outer():
    x = "outer variable"

    def inner():
        nonlocal x
        x = "modified by inner"
        print("Inner:", x)

    inner()
    print("Outer:", x)

outer()

Output:

Inner: modified by inner
Outer: modified by inner

Summary Table