Global Keyword in Python

February 18, 2021

Global Keyword

In Python programs, different variables have different scopes. The variable may or may not be accessible inside a function depending on where it is declared. A global keyword is a keyword that allows user to modify a variable outside of the current scope.It is used to create global variables from a non-global scope i.e inside a function.

Syntax

global myVariable

Use of Global Keyword

Global keyword is used inside a function only when we want to do assignments or when we want to change a variable. Global is not needed for printing and accessing.

Without Using Global Keyword

#global variables
a=5
b=10

#function to add the variables
def add():
    c=a+b
    return c

#calling function
print(add())

Output :

15

In the above example we are accessing the global variable, but if we want to assign a new value then we can not do this by declaring the variable globally.

# global variable
myVar = 321

# function to update the variable
def update():
    myVar= myVar * 2
    print(myVar)

# calling the function
update()

Output :

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
UnboundLocalError: local variable 'myVar' referenced before assignment

Using Global Keyword

# global variable
myVar = 321

# function to update the variable
def update():
    global myVar
    myVar= myVar * 2
    print(myVar)

# calling the function
update()

Output :

642