属性方法的作用就是通过@property把一个方法变成一个静态属性
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class
Dog(
object
):
def
__init__(
self
,name):
self
.name
=
name
@property
def
eat(
self
):
print
(
" %s is eating"
%
self
.name)
d
=
Dog(
"ChenRonghua"
)
d.eat()
|
调用会出以下错误, 说NoneType is not callable, 因为eat此时已经变成一个静态属性了, 不是方法了, 想调用已经不需要加()号了,直接d.eat就可以了
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Traceback (most recent call last):
ChenRonghua
is
eating
File
"/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/属性方法.py"
, line
16
,
in
<module>
d.eat()
TypeError:
'NoneType'
object
is
not
callable
|
正常调用如下
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d
=
Dog(
"ChenRonghua"
)
d.eat
输出
ChenRonghua
is
eating
|
好吧,把一个方法变成静态属性有什么卵用呢?既然想要静态变量,那直接定义成一个静态变量不就得了么?well, 以后你会需到很多场景是不能简单通过 定义 静态属性来实现的, 比如 ,你想知道一个航班当前的状态,是到达了、延迟了、取消了、还是已经飞走了, 想知道这种状态你必须经历以下几步:
1. 连接航空公司API查询
2. 对查询结果进行解析
3. 返回结果给你的用户
因此这个status属性的值是一系列动作后才得到的结果,所以你每次调用时,其实它都要经过一系列的动作才返回你结果,但这些动作过程不需要用户关心, 用户只需要调用这个属性就可以,明白 了么?
class Flight(object): def __init__(self,name): self.flight_name = name def checking_status(self): print("checking flight %s status " % self.flight_name) return 1 @property def flight_status(self): status = self.checking_status() if status == 0 : print("flight got canceled...") elif status == 1 : print("flight is arrived...") elif status == 2: print("flight has departured already...") else: print("cannot confirm the flight status...,please check later") f = Flight("CA980") f.flight_status
cool , 那现在我只能查询航班状态, 既然这个flight_status已经是个属性了, 那我能否给它赋值呢?试试吧
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f
=
Flight(
"CA980"
)
f.flight_status
f.flight_status
=
2
|
输出, 说不能更改这个属性,我擦。。。。,怎么办怎么办。。。
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checking flight CA980 status
flight
is
arrived...
Traceback (most recent call last):
File
"/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/属性方法.py"
, line
58
,
in
<module>
f.flight_status
=
2
AttributeError: can't
set
attribute
|
当然可以改, 不过需要通过@proerty.setter装饰器再装饰一下,此时 你需要写一个新方法, 对这个flight_status进行更改。
class Flight(object): def __init__(self,name): self.flight_name = name def checking_status(self): print("checking flight %s status " % self.flight_name) return 1 @property def flight_status(self): status = self.checking_status() if status == 0 : print("flight got canceled...") elif status == 1 : print("flight is arrived...") elif status == 2: print("flight has departured already...") else: print("cannot confirm the flight status...,please check later") @flight_status.setter #修改 def flight_status(self,status): status_dic = { 0 : "canceled", 1 :"arrived", 2 : "departured" } print("\033[31;1mHas changed the flight status to \033[0m",status_dic.get(status) ) @flight_status.deleter #删除 def flight_status(self): print("status got removed...") f = Flight("CA980") f.flight_status f.flight_status = 2 #触发@flight_status.setter del f.flight_status #触发@flight_status.deleter
注意以上代码里还写了一个@flight_status.deleter, 是允许可以将这个属性删除