Using global keyword in Python programming language

While Python has the scope of variables defined within a function, using the global keyword ensures that the variable being accessed is from the global module, hence avoiding the creation of a local variable with the same name as the global variable. Using global keyword allows for code re-usability, readability, and maintainability. This tutorial will focus on how to use the global keyword in Python programming and its practical applications. By the end of the tutorial, you will have a solid understanding of global keyword and how to use them in your Python projects.

Global Keyword

• We have already read about global and local variables in python.
•  We know that global variables are variables that are declared outside of any function. 
• Global variables can be accessed from anywhere in your code, inside or outside of functions. 
• In Python, global variables are declared using the  global  keyword. 
• Note # : Note that we need to use the global keyword only if
  • we want to modify the global variable.
  • or we want to assign some value to the global variable.
• We do not need to use the global keyword for printing or accessing the global variables.
• Python interpreter treats any variable changed or created inside a function as a local variable unless it is explicitly declared as global.

Accessing a Global Variable : 

• Here is a sample code for accessing global variables from a function : 
• Note # : 
  • Note that we can easily access global variables from a function
  • Using a global keyword is not necessary for accessing global variables.
• Sample Code :

glb = "I am Global."

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

my_func() 

# Output: 
# Accessing global from inside :  I am Global. 

Modifying Global variable :

We can modify a global variable by two methods :

• without using global keyword
• using global keyword

Modifying global variable without using global keyword

• If you try to modify a global variable inside a function, without using the  global  keyword.
• Note # : 
  • Note that value of glb has changed only inside  my_func .
  • We have not used global keyword
  • Hence  glb  is treated as a local variable within  my_func .
  • Outside the function the value of  glb  is still the same.
• Sample Code : 

glb = "I am Global"

def my_func(): 
	glb = "I am local"
	print("Accessing global from inside : ", glb) 

my_func() 
print("Accessing global from outside : ", glb) 

# Output: 
# Accessing global from inside :  I am local
# Accessing global from outside :  I am Global




 

Modifying global variable using global keyword

• If you try to modify a global variable inside a function using the  global  keyword.
• Note # : 
  • Note that value of  glb  has changed outside  my_func  as well.
  • We have used  global  keyword
  • Hence  glb  is treated as a global variable within  my_func  as well.
• Sample Code : 

glb = "I am Global"

def my_func(): 
	global glb
	glb = "I am local"
	print("Accessing global from inside : ", glb) 

my_func() 
print("Accessing global from outside : ", glb) 

# Output: 
# Accessing global from inside :  I am local
# Accessing global from outside :  I am local