Use _slots_ variable class instance attributes can be added to limit the

Property if we want to limit the instances of how to do? For example, only add Student instance nameand ageattributes.

Then we add _slots_ variables inside the Student class

E.g:

class Student (Object):
     __slots__ is = ( ' name ' , ' Age ' ) # a tuple attribute name definition allows binding

Then, we try:

S = Student >>> () # create a new instance 
>>> s.name = ' Michael '  # add attribute 'name' 
>>> s.age = 25 # add attribute 'Age' 
>>> = s.score 99 # Add property 'Score' 
Traceback (MOST Recent Last Call): 
  File " <stdin> " , Line. 1, in <Module1> 
AttributeError: ' Student ' Object attribute has NO ' Score '

When we add the property to s score instance, an error occurs, then the limit _slots_ variable success. Because the 'score' property is not placed in _slots_.

Note: The __slots__attributes defined only for the current class instance acts on the subclass inherits is ineffective unless define subclasses _slots_.