python 面向对象六动态添加方法 __slots__限制动态添加方法 - Python

提示：扫一扫查出行
【扫一扫了解最新限行尾号】
复制提示

一、动态添加属性

 >>> class Student(object):

     pass

 >>> st = Student()

 >>> st.name = 'Jack'

 >>> st.name

 'Jack'

二、动态给实例添加方法

 >>> from types import MethodType

 >>> class Student(object):

     pass

 >>> def set_age(self, age):

     self.age = age

 >>> st.set_age = MethodType(set_age, st)   # 给实例绑定一个方法

 >>> st.set_age(25)

 >>> st.age

 25

三、动态给类添加方法

 >>> class Student(object):

     pass

 >>> def set_score(self, score):

     self.score = score

 >>> Student.set_score = set_score

 >>> s1 = Student()

 >>> s1.set_score(100)

 >>> s1.score

 100

 >>> s2 = Student()

 >>> s2.set_score(50)

 >>> s2.score

 50

四、限制实例的属性 __slots__

 >>> class Student(object):

     __slots__ = ('name', 'age')   # 用tuple定义允许绑定对的属性名称

 >>> s = Student()

 >>> s.name = 'Jack'

 >>> s.age = 20

 >>> s.score = 100

 Traceback (most recent call last):

   File "<pyshell#53>", line 1, in <module>

     s.score = 100

 AttributeError: 'Student' object has no attribute 'score'

__slots__ 定义的属性仅对当前类实例起作用，对继承的子类是不起作用的：

 >>> class GraduateStudent(Student):

 ...     pass

 ...

 >>> g = GraduateStudent()

 >>> g.score = 9999

除非在子类中也定义 __slots__ ，这样，子类实例允许定义的属性就是自身的 __slots__ 加上父类的 __slots__：

 >>> class GraduateStudent(Student):

     __slots__ = ('score', )

 >>> g = GraduateStudent()

 >>> g.score = 100

 >>> g.name = 'Mike'

 >>> g.age = 10

 >>> g.other = 'abc'

 Traceback (most recent call last):

   File "<pyshell#69>", line 1, in <module>

     g.other = 'abc'

 AttributeError: 'GraduateStudent' object has no attribute 'other'