python 舊類中使用property特性的方法

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在python中，我們可以攔截對象的所有特性訪問。通過這種攔截的思路，我們可以在舊式類中實現property方法。

__getattribute__(self, name) #當特性name被訪問時自動調用（只能在新式類中使用）__getattr__(self, name) #當特性name被訪問且對象沒有相應的特性時被自動調用__setattr__(self, name, value) #當試圖給特性name賦值時會被自動調用__delattr__(self, name) #當試圖刪除特性name時被自動調用#*相比於使用property有點複雜，但是特殊方法用途很廣

下面是舉例：

class Demo5(object):    def __init__(self):        print("這是建構函式")        self._value1 = None        self._value2 = None    def __setattr__(self, key, value):        print("try to set the value of the  %s property" % (key,))        if key == ‘newValue‘:            self._value1, self._value2 = value        else:            print("the property key is not newValue, now create or set it through __dict__")            self.__dict__[key] = value    def __getattr__(self, item):        print("try to get the value of %s " % (item,))        if item == ‘newValue‘:            return self._value1, self._value2        else:            print("the %s item is not exist" % (item,))            #raise AttributeError    def __delattr__(self, item):        if item == ‘newValue‘:            print("delete the value of newValue")            del self._value1            del self._value2        else:            print("delete other values ,the value name is %s" % item)if __name__ == "__main__":    testDemo = Demo5()    print(testDemo.newValue)    testDemo.newValue = "name","helloworld"    print("print the value of property:", testDemo.newValue)    print(testDemo.notExist)    del testDemo.newValue

下面是結果：

這是建構函式try to set the value of the  _value1 propertythe property key is not newValue, now create or set it through __dict__try to set the value of the  _value2 propertythe property key is not newValue, now create or set it through __dict__try to get the value of newValue (None, None)try to set the value of the  newValue propertytry to set the value of the  _value1 propertythe property key is not newValue, now create or set it through __dict__try to set the value of the  _value2 propertythe property key is not newValue, now create or set it through __dict__try to get the value of newValue (‘print the value of property:‘, (‘name‘, ‘helloworld‘))try to get the value of notExist the notExist item is not existNonedelete the value of newValuedelete other values ,the value name is _value1delete other values ,the value name is _value2

**其實，我們可以發現在使用__setatter__ , __getatter__,__delatter__這些介面時會對其他的值造成影響，因為這個是通用的必須調用的介面。

python 舊類中使用property特性的方法