Python 3.x Python对象属性命名

关于Python类/对象属性，我有一个问题要问。看看这段代码：

class Car:
    def __init__(self, year, model):
        self.__year_model = year
        self.__make = model
        self.__speed = 0 
    def Accelerate(self):
        self.__speed += 5
    def Brake(self):
        self.__speed -= 5
    def get_speed(self):
        print(f"The current speed of this car is {self.__speed} miles")

myCar = Car(2019, 'toyota'.title())
print(f"The name of the car is {myCar.__make} and the manufacturing date is {myCar.__year_model} ")

myCar.Accelerate()
myCar.get_speed()
myCar.Brake()
myCar.get_speed()

从Python解释器运行时，我得到一个AttributeError，如下所示：

Traceback (most recent call last):
  File "c:\Users\Gin-san\Untitled-2.py", line 14, in <module>
    print(f"The name of the car is {myCar.__make} and the manufacturing date is {myCar.__year_model}")
AttributeError: 'Car' object has no attribute '__make'

我可以得到为什么代码没有在第一个实例中运行，而是在第二个实例中运行的原因吗？

---

谢谢。

这是因为python中的双下划线表示您在类中声明了一个私有变量。无法从定义的类外部访问此私有变量

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您可以在这里获得更多信息：

在联机阅读和Python 3文档之后。我发现Python解释器通过将classname

\u classname\uu var

放在变量名前面，去掉了任何带有两个前导下划线的变量名。这是为了防止以后扩展类时发生任何冲突

因此，第一个代码应该是：

class Car:
    def __init__(self, year, model):
        self.__year_model = year
        self.__make = model
        self.__speed = 0 
    def Accelerate(self):
        self.__speed += 5
    def Brake(self):
        self.__speed -= 5
    def get_speed(self):
        print(f"The current speed of this car is {self.__speed} miles")

myCar = Car(2019, 'toyota'.title())
print(f"The name of the car is {myCar._Car__make} and the manufacturing date is {myCar._Car__year_model}")

myCar.Accelerate()
myCar.get_speed()
myCar.Brake()
myCar.get_speed()

请注意，调用时，

\u year\u model

和

\u make

已更改为

\u Car\u year\u model

和

\u Car\u make

，以便访问

The name of the car is Toyota and the manufacturing date is 2019
The current speed of this car is 5 miles
The current speed of this car is 0 miles

class Car:
    def __init__(self, year, model):
        self.__year_model = year
        self.__make = model
        self.__speed = 0 
    def Accelerate(self):
        self.__speed += 5
    def Brake(self):
        self.__speed -= 5
    def get_speed(self):
        print(f"The current speed of this car is {self.__speed} miles")

myCar = Car(2019, 'toyota'.title())
print(f"The name of the car is {myCar._Car__make} and the manufacturing date is {myCar._Car__year_model}")

myCar.Accelerate()
myCar.get_speed()
myCar.Brake()
myCar.get_speed()