Access and modify global variable

 # Trying to change global variable

my_surname = 'Chakraborti'


def change_my_surname():
    my_surname = 'Chakraborty'


print(f"My Surname before change: {my_surname}")
# Call change my surname function
change_my_surname()
print(f"My Surname after change: {my_surname}")

Output:

My Surname before change: Chakraborti
My Surname after change: Chakraborti

The above code could not change the my_surname (global variable). 

Actually in the change_my_surname() function,

it is creating a local variable.

This can be verified just writing a print statement.

# Access global variable
my_surname = 'Chakraborti'



def change_my_surname():
    my_surname = 'Chakraborty'
    print(f"Changing surname to: {my_surname}")


print(f"My Surname before change: {my_surname}")
# Call change my surname function
change_my_surname()
print(f"My Surname after change: {my_surname}")
Output:
My Surname before change: Chakraborti
Changing surname to: Chakraborty
My Surname after change: Chakraborti

However, inside function, we can access the value.
# Access global variable
my_surname = 'Chakraborti'



def change_my_surname():
    print(f"Current Surname: {my_surname}")


change_my_surname()

Output:
Current Surname: Chakraborti
Now to change the global variable,

# Change global variable
my_surname = 'Chakraborti'

def change_my_surname():
    global my_surname
    my_surname = 'Chakraborty'
    print(f"Changing surname to: {my_surname}")


print(f"My Surname before change: {my_surname}")
# Call change my surname function
change_my_surname()
print(f"My Surname after change: {my_surname}")
Output:
My Surname before change: Chakraborti
Changing surname to: Chakraborty
My Surname after change: Chakraborty