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！
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1
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class
property
(fget
=
None
, fset
=
None
, fdel
=
None
, doc
=
None
)
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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：
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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
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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：
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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：
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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”。
本文转自戴柏阳的博客博客51CTO博客，原文链接http://blog.51cto.com/daibaiyang119/1972460如需转载请自行联系原作者
daibaiyang119
