Python学习(十三)--@property和property函数

Posted 2020-12-02 木九九

• @property

        @property装饰器可以把一个方法变成属性调用。

 

        举一个例子，对学生成绩进行设置和查询。通过set_score来设置成绩，get_score来获取成绩。这样的不方便之处就是不像直接用属性那么方便。

class Student(object):
 
    def get_score(self):
        return self._score
 
    def set_score(self, value):
        if not isinstance(value, int):
            raise ValueError(‘score must be an integer!‘)
        if value < 0 or value > 100:
            raise ValueError(‘score must between 0 ~ 100!‘)
        self._score = value

 

然后通过@property装饰器重新修改后：

class Student(object):
 
    @property
    def score(self):
        return self._score
 
    @score.setter
    def score(self, value):
        if not isinstance(value, int):
            raise ValueError(‘score must be an integer!‘)
        if value < 0 or value > 100:
            raise ValueError(‘score must between 0 ~ 100!‘)
        self._score = value
 
>>> s = Student()
>>> s.score = 60 # OK，实际转化为s.set_score(60)
>>> s.score # OK，实际转化为s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
  ...
ValueError: score must between 0 ~ 100!

 

        把一个getter方法变成属性，只需要加上@property。@property本身又创建了另外一个装饰器@score.setter，把一个setter方法变成属性赋值。

 

 

 

• property函数

        property函数的原理和@property很相似，它有四个参数。

        property(fget=None, fset=None, fdel=None, doc=None)

class Student(object):
 
    def get_score(self):
        return self._score
 
    def set_score(self, value):
        if not isinstance(value, int):
            raise ValueError(‘score must be an integer!‘)
        if value < 0 or value > 100:
            raise ValueError(‘score must between 0 ~ 100!‘)
        self._score = value
 
    score = property(fget=get_score, fset=set_score)
 
>>> s = Student()
>>> s.score = 60 # OK，实际转化为s.set_score(60)
>>> s.score # OK，实际转化为s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
  ...
ValueError: score must between 0 ~ 100!

 

 

参考：

https://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/001386820062641f3bcc60a4b164f8d91df476445697b9e000