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In this Python tutorial, we are going to explain the concept of local variables. A local variable is declared inside a function of a program and it is accessible only from within the same function i.e. from the inside of the same function and not outside it.

The memory given to a local variable is taken away as soon the control goes outside the function(in which the local variable is defined). Consequently, we could say that local variables have a local scope.

In order to understand the concept of local variables, we are going to explain how we can declare, initialize, access and pass the values of local variables. So, let us see how it is done in the upcoming Python programs.

• Example - Local Variables


In the upcoming program, we are going to declare, initialize some local variables within a function named show_values(), these variables will be accessed from within the same function when it is called.

Note : The local variables are always defined(declared and initialized) inside the function of a program.



# Python - Local variables



# Defining the function show_values()
def show_values():

    # Declaring and initializing local variables of the function
    year = 2019
    message = 'Have a good day!'
    time = '17:09'
    
    print('year : ', year)
    print('message : ', message)
    print('time : ', time)

	

# Calling the show_values() function
show_values()





Output-




year :  2019
message :  Have a good day!
time :  17:09


As you can see in the output, we have called a function show_values(), which has accessed and printed the values of its own local variables defined in it.







• Local variables cannot be accessed outside its scope


Local variables are always defined within a function, hence they cannot be accessed outside it, doing so gives an error. Let us see how.



# Python - Trying to access a local variable outside its scope



# Defining the function show_message()
def show_message():

    # Declaring and initializing local variables of the function
    message = 'Have a good life!'
	
    # Printing value of a local variable within its function
    print('message : ', message)
  


# Calling the show_message() function
show_message()

# Trying to access a local variable from the outside its scope/function
print('message : ', message)





Output




message :  Have a good life!
time :  17:09
Traceback (most recent call last):
  File "D:/Python Programs/local2.py", line 20, in 
    print('message : ', message)
NameError: name 'message' is not defined


As you can see in the output of the program, there was no problem in printing the values of its local variable as long as the control of the program was inside their function i.e. show_message(), but trying to access a local variable message outside its function has raised an error i.e. NameError.




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• Local variable can shadow a global variable


Local variables in a function having the same name as global variables will overshadow the global variables.



# Python - Trying to change values of global variables

fruit = 'Apple'
quantity = 2
price =  10.99

   


# Declaring local variables with the same name as global variables in a function,
# overshadows  global variables but does not impact the original values of global variables.
def mango_info():
    fruit = 'Mango'
    quanity = 5
    price =  15.99
    print('Printing the values of local variables :')
    print('fruit  : ', fruit)
    print('quantity : ', quantity)
    print('price : ', price)

    

# Calling the fruit_info() function
mango_info()

print('Printing the values of global variables :')
print('fruit : ', fruit)
print('quantity : ', quantity)
print('price : ', price)





Output

Printing the values of local variables :
fruit  :  Mango
quantity :  2
price :  15.99
Printing the values of global variables :
fruit :  Apple
quantity :  2
price :  10.99


Within the function mango_info(), we have declaring local variables with the same name as global variables, hence the local variables have overshadowed global variables and giving values to these local variables has not impacted the original values of global variables.






• Passing the values of local variables between functions


We can use the values of local variables outside the function in which they are defined, by passing their values to other functions when these functions are called.



# Python - Passing values of local variables


def add(x,y):
    result = x + y
    return result


def subtract(x,y):
    result = x - y
    return result


def multiply(x,y):
    result = x * y
    return result


def do_math():
    a = 10
    b = 25.5
    sum = add(a,b)
    print('sum : ', sum)
    sum = subtract(a,b)
    print('difference : ', sum)
    sum = multiply(a,b)
    print('multiplication : ', sum)

# Calling a function func()
do_math()





Output




sum :  35.5
difference :  -15.5
multiplication :  255.0


Values of local variables declared within the function do_math() are passed to the functions add(), subtract() and multiple().






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