None in Python

This constant is the only value for the type NoneType .

None is usually used to indicate that that there is no specific meaning. 
For example, to designate a default parameter of a function.

  # Can’t assign a value 
 None = 10 # SyntaxError: can’t assign to keyword 
 
 # Use as default parameter value. 
 def print_some (value = None): 
 # If no value is passed, use some. 
 value = value or ’some’ 
 print (value) 
 
 print_some () # some 
 
 # Checks for None 
 # are done with is, not == 
 if something is None: 
 pass 
 
 if something is not None: 
 pass