In this tutorial, you will two very important variable types in Python which are- Global and Local variables. First of all, we will take a look at global variables and then focus on local variables.
Variables that are declared outside a function and are accessible to all the functions are called global variables. In other words, you can access global variables outside and inside a function.
x = 10
def display():
print('Value of x inside function: ', x)
display()
print('Value of x outside function: ', x)
Output of the above program
Value of x inside function: 10 Value of x outside function: 10
In the above code, we have declared a global variable x and displayed its value inside display() function.
What will happen if you try to change the value of x inside a function?
x = 10
def display():
x = x + 15
print('Value of x inside function: ', x)
display()
Output of the above program
UnboundLocalError: local variable 'x' referenced before assignment
If you try to change the value of the global variable inside a function, then you will get UnboundLocalError error. You will get this error because Python considers variable x as a local variable and x is not defined inside display() function. To get around this problem, you need to declare it using global keyword.
x = 10
def display():
global x
x = x + 15
print('Value of x inside function: ', x)
display()
print('Value of x outside function: ', x)
Output of the above program
Value of x inside function: 25 Value of x outside function: 25
Local variables are declared inside a function and are only accessible to that function. In other words, local variables cannot be accessed by other functions. If in case you try to access local variable outside a function, then you will get NameError error.
def show():
x = "I am a local variable"
print('Value of x: ', x)
show()
print('Value of x outside function: ', x)
Output of the above program
Value of x: I am a local variable NameError: name 'x' is not defined
As you can see above that we cannot access the local variable outside the function.
x = "I am a global variable"
def show():
# Variable 'x' is redefined as a local variable.
x = "I am a local variable"
print('Value of x: ', x)
def display():
global x
x = "I am still a Global variable"
print('Value of x: ', x)
y = "I am a local variable"
print('Value of y: ', y)
show()
print('Value of x: ', x)
display()
print('Value of x: ', x)
Output of the above program
Value of x: I am a local variable Value of x: I am a global variable Value of x: I am still a Global variable Value of y: I am a local variable Value of x: I am still a Global variable
show() function has redefined global variable x as a local variable. So modifying x will not change the value of global variable x. After show() function, we have displayed the value of x to check whether its value is changed or not.
To modify global variable x inside display() function, we have declared it global and then changed its value. The updated value is displayed inside as well as outside display() function.
