[Python知识库]16_python_类运算符——重载（三）

# __init__构造方法
class Car:
    def __init__(self,name,color):
        self.name = name
        self.color = color
    def run(self):
        print('%s is on the road!!!'% car.name)

        
car  = Car('tesila','red')
car.run()
    

tesila is on the road!!!

#重载
class Motor(Car):
        def __init__(self,name,speed):
            Car.__init__(self,name,'black')
            self.speed = speed
            
        def run(self):
            print('%s with %s on the road while with %s km/h!!!'% (self.name,self.color,self.speed))

motor = Motor('ha lei',100)

motor.run()

ha lei with black on the road while with 100 km/h!!!

#__repr__方法
class Hello:
    def __init__(self,words):
        self.words = words
    
        

hello = Hello('hello world!!')

hello

<__main__.Hello at 0x2b6990e8250>

#增加__repr__方法
class Hello:
    def __init__(self,words):
        self.words = words
        
    def __repr__(self):
        return "the word is:%s"% self.words

hello = Hello("hello world")

hello

the word is:hello world

# __setitem__ 和 __getitem__ 方法的使用
class Numbers:
    def __init__(self,value):
        self.value = value

L = Numbers([10,9,8,7,6,5,4,3,2])

L.value

[10, 9, 8, 7, 6, 5, 4, 3, 2]

L[0]

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

~\AppData\Local\Temp/ipykernel_10788/3817280154.py in <module>
----> 1 L[0]


TypeError: 'Numbers' object is not subscriptable

#使用__setitem__ 和 __getitem__ 
class Numbers:
    def __init__(self,value):
        self.value = value
        
    def __getitem__(self,i):
        return self.value[i]
    
    def __setitem__(self, key, value):
        self.value[key] = value
        

L = Numbers([10,9,8,7,6,5,4,3,2])

L[0]

10

L[0] = 100

L[0]

100

#   __len__方法
class words:
    def __init__(self,name):
        self.name = name
    def __len__(self):
        return len(self.name)

w = words("huanle")

len(w)

6

#   当没有__len__方法时候
class words:
    def __init__(self,name):
        self.name = name

w = words("huanle")

len(w)                         #没有__len___方法就会报错

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

~\AppData\Local\Temp/ipykernel_10788/2910865679.py in <module>
----> 1 len(w)


TypeError: object of type 'words' has no len()