__slots__的作用

限制实例属性,但是对子类的实例无效

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Student(object):
    __slots__ = ('name', 'age')  # 用tuple定义允许绑定的属性名称


class GraduateStudent(Student):
    pass


s = Student()  # 创建新的实例
s.name = 'Michael'  # 绑定属性'name'
s.age = 25  # 绑定属性'age'
# ERROR: AttributeError: 'Student' object has no attribute 'score'
try:
    s.score = 99
except AttributeError as e:
    print('AttributeError:', e)

g = GraduateStudent()
g.score = 99
print('g.score =', g.score)