Python3 property属性

python3中的property有一个很有意思的功能，它能将类中的方法像类属性一样调用！

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

我们先来简单了解一下这个property类，下面看一下官网给出的例子：

class C:
    def __init__(self):
        self._x = None

def getx(self):
        return self._x

def setx(self, value):
        self._x = value

def delx(self):
        del self._x

x = property(getx, setx, delx, "I'm the 'x' property.")  # 这里的x相当于类属性
   
c = C()  # 生成一个对象
c.x = 10  # 设置self._x=10，实际调用的就是类中setx方法
c.x  # 获取self._x的值，实际调用的就是类中getx方法
del c.x  # 删除self._x的值，实际调用的就是类中delx方法

    是不是感觉很有意思，很不可思议！property中fget是一个函数，它获取属性值；fset是一个函数,它设置一个属性值；fdel是一个函数,它删除一个属性值；doc为该属性创建一个docstring。你只要在使用时在对应的形参位置放上你写的对应函数，就可以轻松使用了。

 

我们还可以将property作为装饰器来使用，还是使用官网的例子：

class C:
    def __init__(self):
        self._x = None

@property
    def x(self):
        """I'm the 'x' property."""
        return self._x

@x.setter
    def x(self, value):
        self._x = value

@x.deleter
    def x(self):
        del self._x

    property对象有getter、setter、deleter三个方法，getter获取属性值，setter设置属性值，deleter设置属性值，这个例子的效果跟上一个例子的效果完全相同！我们看到里面的方法名是一模一样的，但是达到的效果却是不同的。第一个x方法是获取属性值，第二个x方法是设置属性值，第三个x方法是删除属性值。

    你看到这里是不是以为这一切都是property帮你做到的，错，错，错！其实property只做了一件事件，它将你的方法能像类属性一样使用，至于里面的查、删、改，其实都是你自己写的函数实现的！fget、fset、fdel、setter、deleter这些仅仅只是名字而且，方便你识别，其他什么作用都没有！

我们来看一下property的源代码：

class property(object):
    """
    property(fget=None, fset=None, fdel=None, doc=None) -> property attribute
   
    fget is a function to be used for getting an attribute value, and likewise
    fset is a function for setting, and fdel a function for del'ing, an
    attribute.  Typical use is to define a managed attribute x:
   
    class C(object):
        def getx(self): return self._x
        def setx(self, value): self._x = value
        def delx(self): del self._x
        x = property(getx, setx, delx, "I'm the 'x' property.")
   
    Decorators make defining new properties or modifying existing ones easy:
   
    class C(object):
        @property
        def x(self):
            "I am the 'x' property."
            return self._x
        @x.setter
        def x(self, value):
            self._x = value
        @x.deleter
        def x(self):
            del self._x
    """
    def deleter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the deleter on a property. """
        pass

def getter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the getter on a property. """
        pass

def setter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the setter on a property. """
        pass

def __delete__(self, *args, **kwargs): # real signature unknown
        """ Delete an attribute of instance. """
        pass

def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

def __get__(self, *args, **kwargs): # real signature unknown
        """ Return an attribute of instance, which is of type owner. """
        pass

def __init__(self, fget=None, fset=None, fdel=None, doc=None): # known special case of property.__init__
        """
        property(fget=None, fset=None, fdel=None, doc=None) -> property attribute
       
        fget is a function to be used for getting an attribute value, and likewise
        fset is a function for setting, and fdel a function for del'ing, an
        attribute.  Typical use is to define a managed attribute x:
       
        class C(object):
            def getx(self): return self._x
            def setx(self, value): self._x = value
            def delx(self): del self._x
            x = property(getx, setx, delx, "I'm the 'x' property.")
       
        Decorators make defining new properties or modifying existing ones easy:
       
        class C(object):
            @property
            def x(self):
                "I am the 'x' property."
                return self._x
            @x.setter
            def x(self, value):
                self._x = value
            @x.deleter
            def x(self):
                del self._x
       
        # (copied from class doc)
        """
        pass

@staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

def __set__(self, *args, **kwargs): # real signature unknown
        """ Set an attribute of instance to value. """
        pass

fdel = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

fget = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

fset = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

__isabstractmethod__ = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    看到上面的源代码恍然大悟没，fdel、fget、fset都只是执行你函数里面的代码而已！所以我们就记住一句话就够了：“property能让你的方法像类属性一样使用”。