property

简单使用

class Student:

    def get_score(self):
        return self._score

    def set_score(self, newscore):
        if not isinstance(newscore, int):
            raise ValueError('score must be integer')
        elif newscore < 0 or newscore > 100:
            raise ValueError('score must between 0 ~ 100')
        else:
            self._score = newscore


s = Student()
s.set_score(88)
print(s.get_score())
## s.set_score(10000)  ## 数字太大会报错

## 下面是使用@property改进
class Student1():

    ## getter的方法名 score
    ## @property getter
    @property
    def score(self):
        return self._score

    ## setter的方法名score
    ## @score.setter 是 setter
    @score.setter
    def score(self, newscore):
        if not isinstance(newscore, int):
            raise ValueError('score must be integer')
        elif newscore < 0 or newscore > 100:
            raise ValueError('score must between 0 ~ 100')
        else:
            self._score = newscore

s1 = Student1()
s1.score = 60
print(s1.score)
## s1.score = 1000  ## 数字太大会报错

1. get/set 方法名是属性 score
2. @property 是 getter, @score.setter 是 setter

只读属性

class Student:

    @property
    def birth(self):
        return self._birth

    @birth.setter
    def birth(self, birth):
        self._birth = birth

    @property
    def age(self):
        return 2015 - self.birth

1. age 只有 @property 是只读属性

属性名和方法不要重复

class Student:
    
    @property
    def birth(self):
        return self.birth

这是因为调用s.birth时，首先转换为方法调用，在执行return self.birth时，又视为访问self的属性，于是又转换为方法调用，造成无限递归，最终导致栈溢出报错RecursionError。

测试

## 测试
class Screen:

    @property
    def width(self):
        return self._width

    @width.setter
    def width(self, new_wid):
        self._width = new_wid

    @property
    def height(self):
        return self._height

    @height.setter
    def height(self, new_hei):
        self._height = new_hei


    @property
    def resolution(self):
        return self._height * self._width
## 测试:
s = Screen()
s.width = 1024
s.height = 768
print('resolution =', s.resolution)
if s.resolution == 786432:
    print('测试通过!')
else:
    print('测试失败!')