how to declare and update a global variable in python code example

Example 1: global variable python

a = 0

def testFor():
  global a 
  if(a == 0):
    	#run code

Example 2: python local variables

'''Local variables are those that are defined in a block '''
a = 1 #This is NOT a local variable, this is a global variable
def add():
  b = 1 #This IS a local variable
  print(b)
add()
#If we tried to print(b) outside of the add() function, we would get an error