Global and local variables

Local variables only work in the function, global variables work in the whole function 
def logger ():
     ' Log function ' 
    pass 
def home ():
    logger()
    print('home')
def index():
    logger()
    print('index')

function and calling function 
name= ' cat '

def change_name():
    name='dog'
    print('my name is ',name)
change_name()

Modify global variables with global ... 
name= ' cat '

def change_name():
    global name
    name='dog'
    print('my name is ',name)
change_name()