Question

每当object.x更新时，请制作一些重新计算object._x的代码。我打算将object._x作为object和object.x的“私有”属性作为“虚拟变量”，其唯一目的是设置object._x的值。

class tihst(object):
    def __init__(self,object):
        self.x=object
        self.xRecall()
    def xPrivate(self):
        if type(self.x)==float:
            self._x=self.x
        elif type(self.x)==int:
            self._x=float(self.x)
        elif type(self.x)==str:
            self._x=self.x
        else:
            self._x="errorStatus001"
    def xRecall(self):
        print "private x is :"
        self.xPrivate()
        print self._x

aone=tihst("002")
print vars(aone)

例如：如果用户发表object.x="5.3"之类的陈述，那么指令object.xPrivate()也应该发生。

Answer 1

听起来我希望x成为property。属性是您存储在调用＆＃34; getter＆＃34;的类中的对象。和＆＃34; setter＆＃34;函数在访问时或作为类的实例上的属性分配。

试试这个：

class MyClass(object):
    def __init__(self, val):
        self.x = val   # note, this will access the property too

    @property          # use property as a decorator of the getter method
    def x(self):
        return self._x

    @x.setter          # use the "setter" attribute of the property as a decorator
    def x(self, value):
        if isinstance(value, (float, int, str)):  # accept only these types
            self._x = val
        else:
            self._x = "Error" # it might be more "Pythonic" to raise an exception here

Answer 2

你也可以像这样使用property：

class MyClass(object):

    def __init__(self, x):
        self._x = x

    def access_x(self):
        print 'Accessing private attribute x:', self._x
        return self._x

    def change_x(self, new_x):
        print 'Changing private attribute x to', new_x
        # You can add some extra logic here ...
        self._x = new_x

    x = property(access_x, change_x)

您可以通过创建类的实例来查看属性：

>>> obj = MyClass('123')

>>> obj.x
Accessing private attribute x: 123
'123'

>>> obj.x = 456
Changing private attribute x to 456

自动更新一些＆＃34;私人＆＃34;每当修改某个其他实例属性时属性

2 个答案: