◆ 静态方法:
通过@staticmethod装饰器即可把其装饰的方法变为一个静态方法。普通的方法,可以在实例化后直接调用,并且在方法里可以通过self.调用实例变量或类变量。静态方法是不可以访问实例变量或类变量的,它与类唯一的关联就是需要通过类名来调用这个方法。
class Dog(object):
def __init__(self,name):
self.name = name
@staticmethod #把eat方法变为静态方法
def eat(self):
print("%s is eating" % self.name)
d = Dog("ChenRonghua")
d.eat()
上面的调用会出以下错误,说是eat需要一个self参数,但调用时却没有传递,没错,当eat变成静态方法后,再通过实例调用时就不会自动把实例本身当作一个参数传给self了。
Traceback (most recent call last):
File "/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/静态方法.py", line 17, in <module>
d.eat()
TypeError: eat() missing 1 required positional argument: 'self'
想让上面的代码可以正常工作有两种办法
- 调用时主动传递实例本身给eat方法,即d.eat(d)
- 在eat方法中去掉self参数,但这也意味着,在eat中不能通过self.调用实例中的其它变量了
◆ 类方法:
类方法通过@classmethod装饰器实现,类方法和普通方法的区别是, 类方法只能访问类变量,不能访问实例变量
class Dog(object):
def __init__(self,name):
self.name = name
@classmethod
def eat(self):
print("%s is eating" % self.name)
d = Dog("ChenRonghua")
d.eat()
执行报错如下,说Dog没有name属性,因为name是个实例变量,类方法是不能访问实例变量的
Traceback (most recent call last):
File "/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/类方法.py", line 16, in <module>
d.eat()
File "/Users/jieli/PycharmProjects/python基础/自动化day7面向对象高级/类方法.py", line 11, in eat
print("%s is eating" % self.name)
AttributeError: type object 'Dog' has no attribute 'name'
此时可以定义一个类变量,也叫name,看下执行效果
class Dog(object):
name = "我是类变量"
def __init__(self,name):
self.name = name
@classmethod
def eat(self):
print("%s is eating" % self.name)
d = Dog("ChenRonghua")
d.eat()
#执行结果
我是类变量 is eating
◆ 属性方法:
通过@property把一个方法变成一个静态属性
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
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
d = Dog("ChenRonghua")
d.eat
输出
ChenRonghua is eating
★ 属性方法的场景:
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,所以每次调用时,都要经过一系列的动作才返回结果,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。
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
如果需要更改这个属性,需要通过@proerty.setter装饰器再装饰一下。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 = {
: "canceled",
:"arrived",
: "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