Global and Local Variables in Python Programming Language

In the world of programming, variables are one of the most fundamental concepts that must be understood by any aspiring developer. Variables in Python can either be global or local, and it is crucial to know the difference between the two. In this tutorial, we will explore the topic of global and local variables in Python programming language. We will look at what each type of variable is, how they differ, and when to use them. This tutorial is intended for beginners who are just getting started with Python and want to gain a better understanding of how variables work in this powerful language.

Variable Scope : 

• In the tutorial on Namespaces in Python we have read about variable scope.
• Here is a quick reminder of variable scope before we delve into the main topic.
• The scope of a variable is the lifespan of that variable. 
• Variable scope is that section of code in which the variable is meaningful.
• Depending on their scope, variables are divided into :
  • Global variables
  • Local variables

Global Variables in Python : 

• Global variables in Python are those variables which are defined outside any function.
• Global variables have a global scope.
• Global variables can be accessed from all sections of the program.
• Global variables are accessible from all the functions of the code.

Creating global variables in Python

• Lets take a look at how to define and access global variables in python.

def my_func():
   print("Accessing global variable from inside : ", glb)

# This is the Global space
glb = "I am global."
print("Accessing global variable from outside : ", glb)
my_func()

# Output
# Accessing global variable from outside :  I am global.
# Accessing global variable from inside :  I am global.

Local Variables in Python

• Local variables in Python are those variables which are defined within a function.
• Local variables belong only to the function in which it was defined.
• The scope of a local variable is limited to the function in which it is defined. 
• Local variables can be accessed inside that function only in which it was defined.
• Local variables are not accessible from anywhere outside that function.

Creating local variables in Python

• Below is the code to show how to define and access local variables in python.

def my_func():
	lcl = "I am local."
   	print("Accessing local variable from inside : ", lcl)

# This is the Global space
my_func()

# Output
# Accessing local variable from inside :  I am local.

Using local variables outside a function

• We know that local variable cannot be accessed outside the function in which they were defined.
• Let's try to access local variables from outside the function.
• Note # : When we try to access local variable from outside
• We get a  NameError  because the name  lcl  is not known in global space.

def my_func():
	lcl = "I am local."
   	print("Accessing local variable from inside : ", lcl)

# This is the Global space
my_func()
print("Accessing local variable from outside : ", lcl)


# Output
# Accessing local variable from inside :  I am local.
# NameError: name 'lcl' is not defined

Local Variables Vs. Global Variables :

• Below is a tabular summary of differences between local and global variables in Python.