Car类错误

Question

我在解决这个问题上遇到了困难。我得到了两个不同的代码，这就是我遇到麻烦的地方。我在第38行得到一个错误，是"UnboundLocalError:局部变量'year‘在赋值前引用“我不太确定我做错了什么，我是新手，但是非常感谢任何帮助。

class Car:
    def __init__(self, year_model, make, speed):
        self.__year_model = year_model
        self.__make = make
        self.__speed = 0

    ############# year_model################
    def setYear_model(self, year_model):
        self.__year_model = year_model

    def getYear_model(self):
        return self.__year_model

    ############# Make################
    def setMake(self, make):
        self.__make = make

    def getMake(self):
        return self.make

    ############# speed################
    def set_Speed(self, speed):
        if speed < 0:
            print("Speed cannot be negative")
        else:
            self.__speed = speed

    def get_Speed(self):
        return self.__speed

    ############# str ############
    def __str__(self):
        return "Make : " + self.__make + ", Model Year :" + \
            self.__year_model + ", speed =" + str(self.__speed)

    def accelerate(self):
        self.__speed = self.__speed +5

    def brake(self):
        self.__speed = self.__speed -5


def main():

    year=(input('car year: '))
    make=(input('car make: '))
    speed=0
    my_car = Car(year, make, speed)
    print('Current speed is', speed)

    #accelerate 5 times

    my_car.accelerate()
    print('My current speed:',my_car.get_speed())
    my_car.accelerate()
    print('My current speed:',my_car.get_speed())
    my_car.accelerate()
    print('My current speed:',my_car.get_speed())
    my_car.accelerate()
    print('My current speed:',my_car.get_speed())
    my_car.accelerate()
    print('My current speed:',my_car.get_speed())

    #brake five times
    my_car.brake()
    print('My current speed after brake:',my_car.get_speed())
    my_car.brake()
    print('My current speed after brake:',my_car.get_speed())
    my_car.brake()
    print('My current speed after brake:',my_car.get_speed())
    my_car.brake()
    print('My current speed after brake:',my_car.get_speed())
    my_car.brake()
    print('My current speed after brake:',my_car.get_speed())

main()

然后将其连接到此代码。

import ct_CarDefinition

def main():
    # Create an instance of Car
    my_car = ct_CarDefinition.Car("2008", "Honda Accord")

    print(my_car)

main()

Answer 1

试试这个：

def main():
    year=(input('car year: '))
    make=(input('car make: '))
    speed=0
    my_car = Car(year, make, speed)  #use this once you have assigned values for "year", "make", "speed"

另外，在您的类定义中更改以下内容：

class Car:
    def __init__(self, year_model, make, speed):        #add "speed" parameter
        self.__year_model = year_model
        self.__make = make
        self.__speed = 0 

而且，您没有在您的Car类中定义"accelerate“和"brake”方法。因此，使用my_car.accelerate()或my_car.brake()将抛出错误：

AttributeError: Car instance has no attribute 'accelerate'

您可以向Car类添加以下方法：

############# accelerate ################
def accelerate(self):
    self.__speed = self.__speed +5

############# brake ################
def brake(self):
    self.__speed = self.__speed -5

另外，在main方法中调用set_speed和get_speed时，请将名称更改为这两个方法。

############# speed################
def set_speed(self, speed):
    if speed < 0:
        print("Speed cannot be negative")
    else:
        self.__speed = speed

def get_speed(self):
    return self.__speed

输出：

#car year: 1998
#car make: "Honda Accord"
#('Current speed is', 0)
#('My current speed:', 5)
#('My current speed:', 10)
#('My current speed:', 15)
#('My current speed:', 20)
#('My current speed:', 25)
#('My current speed after brake:', 20)
#('My current speed after brake:', 15)
#('My current speed after brake:', 10)
#('My current speed after brake:', 5)
#('My current speed after brake:', 0)