Python Local, Global Variables and Globals Function for Beginners with Examples

In this post, we’ll learn Python Local and Global Variables with Examples for Beginners. Every programming language has its own way of declaring local and global variables. Usually, local variables have local scope i.e they are declared inside a function and global variables are declared outside function or class. Compared to local variables global variables have a larger scope and can be called in any part of the program.

Table of Contents

Introduction

Python Local and Global Variables are used to store value at local and as well as global levels based on program requirements. Many times we require variables that we can use not only inside the function but also outside.

Declaring Local Variables

Variables declared as local can only be used inside a block of code.

def my_func():
    age = 25
    print("Age is : {}".format(age))

my_func()

#PYTHON OUTPUT
Age is : 25
def my_func():
    age = 25

my_func()

print("Age is : {}".format(age))

#PYTHON OUTPUT
NameError: name 'age' is not defined

Python raises the exception NameError when we try to access the local variable age outside the function.

Declaring Global Variables

Global variables can be used inside any function or can be used in other modules.

name = "Clark"

def my_name():
    print("My Name is : {}".format(name))

my_name()

#PYTHON OUTPUT
My Name is : Clark
name = "Clark"
def my_name():
    name = "Bruce"
    print("My Name inside function is : {}".format(name))

my_name()
print("My Name outside function is : {}".format(name))

#PYTHON OUTPUT
My Name inside function is : Bruce
My Name outside function is : Clark

If we try to modify a global variable from inside function than that will create a local variable. To only change the value of the global variable use the global keyword.

name = "Clark"
def my_name():
    global name
    name = "Bruce"
    print("My Name inside function is : {}".format(name))

my_name()
print("My Name outside function is : {}".format(name))

#PYTHON OUTPUT
My Name inside function is : Bruce
My Name outside function is : Bruce

globals() Function

The globals() function is a built-in function in python which contains a dictionary of global variables. Just like a dictionary we can access these variables and update their values.

name = "Suresh"
marks = {
    "English" : 68,
    "Maths" : 56,
    "Science" : 87,
}

def change_marks():
    print("Marks Scored By {}\n".format(name))
    
    for index, subject_marks in globals()['marks'].items():
        subject_marks += 2
        print("{} : {}\n".format(index, subject_marks))


# Dictionary of Global variables
print("Global Variables : {}\n\n".format(globals()))

change_marks()

# Updating value of Global variable 
globals()["marks"]["English"] = 44

#Updated value of english
print("\n\nUpdated Global variable marks english : {}\n\n".format(globals()["marks"]['English']))

    

#PYTHON OUTPUT
Global Variables : {'__cached__': None, '__package__': None, '__file__': 'vars.py', '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x7f23229d9940>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, 'marks': {'English': 68, 'Maths': 56, 'Science': 87}, '__spec__': None, 'change_marks': , 'name': 'Suresh'}

Marks Scored By Suresh

English : 70

Maths : 58

Science : 89           

Updated Global variable marks english : 44

Conclusion

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