span sin .com pre rac turn () 裝飾器 轉化

• @property

@property裝飾器可以把一個方法變成屬性調用。 舉一個例子，對學生成績進行設置和查詢。通過set_score來設置成績，get_score來獲取成績。這樣的不方便之處就是不像直接用屬性那麽方便。

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

然後通過@property裝飾器重新修改後：

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，實際轉化為s.set_score(60)
>>> s.score # OK，實際轉化為s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
  ...
ValueError: score must between 0 ~ 100!

把一個getter方法變成屬性，只需要加上@property。@property本身又創建了另外一個裝飾器@score.setter，把一個setter方法變成屬性賦值。

• property函數

property函數的原理和@property很相似，它有四個參數。 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，實際轉化為s.set_score(60)
>>> s.score # OK，實際轉化為s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
  ...
ValueError: score must between 0 ~ 100!

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

Python學習(十三)--@property和property函數