how to make a global variable using a function in python code example

Example 1: global variable python

a = 0

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

Example 2: global var in python

a = input('Hello: ')
if a == 'world':
  global b
  b = input('Here')
print b
#Prints the input for be as a result