Python 面向对象高级编程——使用@property

1.1   使用@property

输入成绩score时，需对这个参数进行检查。

>>> class Student(object):

...    def get_score(self):

...        return self.__score

...    def set_score(self, value):

...        if not isinstance(value, int):

...             raise ValueError(‘score must beinteger‘)

...        if value < 0 or value > 100:

...             raise ValueError(‘score mustbetween 0 and 100.‘)

...        self.__score = value

...

>>> s = Student()

>>> s.set_score(60)

>>> s.get_score()

60

>>> s.set_score(999)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "<stdin>", line 8, in set_score

ValueError: score must between 0 and 100.

有没有既能检查参数，又可以用类似属性这样简单的方式来访问和修改类的变量呢？

Python内置的@property装饰器就是负责把一个方法变成属性。

>>> class Student(object):

...    @property

...    def score(self):     --score可以理解为属性

...        return self.__score     --返回属性

...    @score.setter

...    def score(self, value):   --score可以理解为属性

...        if not isinstance(value, int):

...             raise ValueError(‘Score must be aninteger.‘)

...        if value < 0 or value > 100:

...             raise ValueError(‘Score mustbetween 0 and 100.‘)

...        self.__score = value    --修改属性

...

>>> s = Student()

>>> s.score = 60    --修改属性，这里不再是调用方法，score属性可读可写

>>> s.score

60

>>> s.score = -1

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "<stdin>", line 10, in score

ValueError: Score must between 0 and 100.

定义只读属性—只定义getter方法，不定义setter就是只读

>>> class Student(object):

...    @property

...    def birth(self):

...        return self._birth

...    @birth.setter

...    def birth(self, value):

...        self._birth = value    --birth可读可写

...    @property

...    def age(self):

...        return 2016 - self._birth    --age只读

...

>>> s = Student()

>>> s.birth = 1992

>>> s.birth

1992

>>> s.age

24