🔍 What is Python Variable Scope?

The scope of a variable refers to the region of the code where that variable is recognized or accessible. Within this scope, you can use the variable without any special prefixes.

Example:

>>> b = 8 >>> def func():        a = 7        print(a)        print(b) >>> func()

Output:

7   8

>>> a

Output:

Traceback (most recent call last):  File "<pyshell#6>", line 1, in <module>    a NameError: name 'a' is not defined

Also, the duration during which a variable exists is called its lifetime.

🔸 Types of Variable Scope in Python

There are 4 main types of variable scope in Python:

Local Scope

Global Scope

Enclosing Scope

Built-in Scope

Let’s explore each of them one by one:

1️⃣ Local Scope in Python

In the previous example, variable a was defined inside the function func. So, a is local to func. It is only accessible within the function, not outside.

Example:

>>> a = 0 >>> def func():        print(a)        a = 1        print(a) >>> func()

Output:

Traceback (most recent call last):  File "<pyshell#79>", line 1, in <module>    func()  File "<pyshell#78>", line 2, in func    print(a) UnboundLocalError: local variable 'a' referenced before assignment

Although a was initially defined globally, the function also tries to define a local variable a, which causes a conflict. This results in an UnboundLocalError.

It's best practice to avoid modifying global variables within functions. Instead, pass them as arguments.

Better approach:

>>> def func(a=0):        a += 1        print(a) >>> func()

Output:

1

2️⃣ Global Scope in Python

A variable defined outside any function or block is considered to be in the global scope.

Example:

>>> b = 5 >>> def show():        print(b) >>> show()

You can access global variables inside functions, but if you want to modify them, you must declare them as global using the global keyword.

3️⃣ Enclosing Scope in Python

This is also called the nonlocal scope. It refers to the scope of a function enclosing another function.

Example:

>>> def red():        a = 1        def blue():            b = 2            print(a)            print(b)        blue()        print(a) >>> red()

Output:

1   2   1

Here, b is local to blue(), while a is nonlocal to blue() but local to red().

4️⃣ Built-in Scope

This is the widest scope, where all built-in names in Python (like print(), id(), etc.) reside. These are available as soon as the Python interpreter is launched—no need to import any module.

🧠 Global Keyword in Python

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

Without global:

>>> a = 1 >>> def counter():        a = 2        print(a) >>> counter()

Output:

2

>>> a

Output:

1

Here, a = 2 inside the function created a new local variable, leaving the global a unchanged.

With global:

>>> a = 1 >>> def counter():        global a        a = 2        print(a) >>> counter()

Output:

2

>>> a

Output:

2

Using global, we tell Python to use the global version of a instead of creating a new local variable.

🧠 Nonlocal Keyword in Python

Similar to global, if you want to modify a variable in the enclosing (nonlocal) scope, use the nonlocal keyword.

Without nonlocal:

>>> def red():        a = 1        def blue():            a = 2            b = 2            print(a)            print(b)        blue()        print(a) >>> red()

Output:

2   2   1

With nonlocal:

>>> def red():        a = 1        def blue():            nonlocal a            a = 2            b = 2            print(a)            print(b)        blue()        print(a) >>> red()

Output:

2   2   2

✅ Python Interview Questions on Variable Scope

What do you mean by scope?

What are the types of variable scope?

What is the scope of a variable with an example?

What are Python variables?

How do you declare a variable in Python 3?

🎯 Conclusion

We hope this guide helped you clearly understand the scope of variables in Python. We covered:

Local Scope

Global Scope

Enclosing (Nonlocal) Scope

Built-in Scope