Output :

UnboundLocalError: local variable 'x' referenced before assignment

This raises errors because python doesn’t allow to change of the global variable inside the function. In order to change the value of a global variable inside a function, we should use the global keyword.

The process of changing the global variable value inside the function is discussed in the article Python Global Keyword. If interested go through it.

Local Variables :

A variable declared in the local scope or inside the function is a local variable.

The scope of the variable is restricted only to the function. It can be accessed only inside the function not anywhere else. Let’s see an example

Code :

def fun():
    x = 3
    print('x inside function is ', x)

fun()
print('x outside fucntion is ', x)

Output :

x inside function is 3
NameError: name 'x' is not defined

The interpreter can able to identify the ‘ x ’ inside the function and cannot identify it outside the function, because ‘ x ‘ is a local variable, its scope is limited only to the function.

Global variable and Local variable having Same Name :

Suppose there is a global variable and local variable with the same name, let’s see what value is taken inside and outside the function.

Code:

def func():
    x = 3
    print('x inside function', x)


x = 5
print('x outside function ', x)
func()

Output :

x outside function 5
x inside function 3

Inside the function, the value of the local variable ‘ x ’ is printed, and outside the function, the global variable ‘ x ’ is printed. The scope of the local variable ‘ x ’ is limited to only the function, So outside the function, the global variable value is printed. Inside the function both local and global variables are accessible.

When a variable is used inside the function, first python checks whether it is declared, inside the function (local scope) or not, if declared then uses local value, else checks whether the variable is global or not. If the variable is global, then uses the global value, if it is neither local nor global variable it raises an error.

Hence Inside the function, the local value is printed, and outside the