Liaoche Python excerpt 7

1. What if we want to restrict the properties of an instance? For example, only add and attributes to student instances are allowed name age .

For the purpose of limiting, Python allows you to define a special variable when defining a class __slots__ to limit the attributes that the class instance can add:

2, use __slots__ to note that the __slots__ defined properties only work for the current class instance, and it does not work for inherited subclasses.

3, in order to limit the scope of score, you can use a set_score() method to set the score, and then through a get_score() to get results, so that in the set_score() method, you can check the parameters

4. Because Python allows multiple inheritance, mixin is a common design.

Only single-inherited languages, such as Java, are allowed to use the mixin design.

5.

This is because the direct display of variable calls is not __str__() , but the __repr__() difference between the two is to return the string that the __str__() user sees, and the __repr__() string that the program developer sees, that __repr__() is, for debugging services.

The solution is to define one more __repr__() . But it's usually __str__() __repr__() the same as the code, so there's a lazy way to do it:

1>>>classStudent (object):2     def __init__(self,name):3Self.name =name4     def __str__(self):5         return"Student Object (name:%s)"%Self.name6     __repr__=__str__7 8     9>>> S=student ('Mike')Ten>>>s OneStudent Object (name:mike)

Liaoche Python excerpt 7