python 子类中扩张超类属性

setting delete

考虑如下的代码，它定义了一个property：

class Person: def init(self, name): self.name = name

# Getter function
@property
def name(self):
    return self._name

# Setter function
@name.setter
def name(self, value):
    if not isinstance(value, str):
        raise TypeError('Expected a string')
    self._name = value

# Deleter function
@name.deleter
def name(self):
    raise AttributeError("Can't delete attribute")

下面是一个示例类，它继承自Person并扩展了 name 属性的功能：

class SubPerson(Person): @property def name(self): print('Getting name') return super().name

@name.setter
def name(self, value):
    print('Setting name to', value)
    super(SubPerson, SubPerson).name.__set__(self, value)

@name.deleter
def name(self):
    print('Deleting name')
    super(SubPerson, SubPerson).name.__delete__(self)

接下来使用这个新类：

s = SubPerson('Guido') Setting name to Guido s.name Getting name 'Guido' s.name = 'Larry' Setting name to Larry s.name = 42 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "example.py", line 16, in name raise TypeError('Expected a string') TypeError: Expected a string

如果你仅仅只想扩展property的某一个方法，那么可以像下面这样写：

class SubPerson(Person): @Person.name.getter def name(self): print('Getting name') return super().name 或者，你只想修改setter方法，就这么写：

class SubPerson(Person): @Person.name.setter def name(self, value): print('Setting name to', value) super(SubPerson, SubPerson).name.set(self, value)