if not python meaning code example

Example 1: python if not true

a = False
if not a:
  #Does this

a = True
if not a:
  #Doesn't do this

Example 2: if not python

a = False
if not a:
    yourFunction()

Example 3: python if not

today = 'Sunday'

if not today=='Sunday':
	print('Go to work.')
else:
	print('Take rest.')