检查列表中特定元素的元素值答案

【问题标题】：Check element value of specific element in list检查列表中特定元素的元素值
【发布时间】：2021-09-25 15:02:58
【问题描述】：

我正在完成一项涵盖课程的作业。有几个要求，但我的程序以目前的方式几乎满足了所有这些要求。该程序将提示用户将汽车或卡车输入他们的虚拟车库。他们从那里选择许多选项，具体取决于它是汽车还是卡车。用户继续执行此操作，直到他们完成添加车辆，然后他们会收到有关他们输入的车辆及其信息的提示。
就目前而言，我可以输入无数的汽车或卡车，它会打印我正确输入的内容。它不允许我进入汽车和卡车，这是我需要它做的。我知道这个问题可能与我的最后一个循环有关，因为它引用了 carTruck 并且它可能应该引用实例列表中元素的值。不过我不确定该怎么做。

我意识到可能有更好的方法来实现这一点，但有一些方法必须根据任务来完成。此外，这里不需要错误处理，因此不包括在内。

class Vehicle:

    def __init__(self, make, model, color, fuelType,options):
        self.make = make
        self.model = model
        self.color = color
        self.fuelType = fuelType
        self.options = options
            
    def getMake(self):
        self.make = input('Please enter the vehicle make: ').title()
        return self.make
        
    def getModel(self):
        self.model = input('Please enter the vehicle model: ').title()
        return self.model

    def getColor(self):
        self.color = input('Please enter the vehicle color: ')
        return self.color

    def getFuelType(self):
        self.fuelType = input('Please enter the vehicle fuel type: ')
        return self.fuelType

    def getOptions(self):
        optionslist = []
        print('\nEnter Y or N for the following options')
        radio = input('Does your vehicle have a radio: ').lower()
        bluetooth = input('Does your vehicle have bluetooth: ').lower()
        cruise = input('Does your vehicle have cruise control: ').lower()
        window = input('Does your vehicle have power windows: ').lower()
        lock = input('Does your vehicle have power locks: ').lower()
        mirror = input('Does your vehicle have power mirrors: ').lower()
        rstart = input('Does your vehicle have remote start: ').lower()
        bcamera = input('Does your vehicle have a back up camera: ').lower()

        if radio == 'y':
            optionslist.append('Radio')
        if bluetooth == 'y':
            optionslist.append('Bluetooth')
        if cruise == 'y':
            optionslist.append('Cruise Control')
        if window == 'y':
            optionslist.append('Power Windows')
        if lock == 'y':
            optionslist.append('Power Locks')
        if mirror == 'y':
            optionslist.append('Power Mirrors')
        if rstart == 'y':
            optionslist.append('Remote Start')
        if bcamera == 'y':
            optionslist.append('Backup Camera')

        self.options = optionslist    
        return self.options

#car child class        
class Car(Vehicle):
    def __init__ (self, make, model, color, fuelType,options, engineSize, numDoors):
        self.engineSize = engineSize
        self.numDoors = numDoors
        Vehicle.__init__(self, make, model, color, fuelType,options)

    def getEngineSize(self):
        self.engineSize = input('Please enter your engine size in liters: ')
        return self.engineSize

    def getNumDoors(self):
        self.numDoors = input('Please enter the number of doors: ')
        return self.numDoors    

#pickup child class
class Pickup(Vehicle):
    def __init__ (self, make, model, color, fuelType,options, cabStyle, bedLength):
        self.cabStyle = cabStyle
        self.numDoors = bedLength
        Vehicle.__init__(self, make, model, color, fuelType, options)

    def getCabStyle(self):
        self.cabStyle = input('Please enter the cab style: ')
        return self.cabStyle

    def getBedLength(self):
        self.bedLength = input('Please enter the bed length: ')
        return self.bedLength   


#creates instance and loops to get info for vehicles from user
instances = []
Exit = 'n'
x = 0
while Exit == 'n':
    carTruck = input('Are you entering a car or truck? ')
    plateNum = input('please enter your license plate number: ')
    instances.append(carTruck + plateNum)

#if statement to use correct class based on user input
    if carTruck == 'car':

        instances[x] = Car('','','','','','','')

        instances[x].getMake()
        instances[x].getModel()
        instances[x].getColor()
        instances[x].getFuelType()
        instances[x].getEngineSize()
        instances[x].getNumDoors()
        instances[x].getOptions()
        if not instances[x].options:
            print('\nYou need to select at least one option.')
            Vehicle.getOptions(instances[x])
        
    elif carTruck == 'truck':
        instances[x] = Pickup('','','','','','','')

        instances[x].getMake()
        instances[x].getModel()
        instances[x].getColor()
        instances[x].getFuelType()
        instances[x].getCabStyle()
        instances[x].getBedLength()
        instances[x].getOptions()
        if not instances[x].options:
            print('\nYou need to select at least one option.')
            Vehicle.getOptions(instances[x])
    
    #allows user to stop adding vehicles
    Exit = input('Are you done adding vehicles (Y/N): ').lower()
    x = x + 1



#loops through instances and provides output dependent on whether it is a car or truck.
b = 0
while b < len(instances):
    if carTruck == 'truck':
        print(f'Your vehicle is a {instances[b].color} {instances[b].make} {instances[b].model} {instances[b].cabStyle} and a {instances[b].bedLength} ft bed that runs on {instances[b].fuelType}.')
        print(f'The options are ' + ", ".join(instances[b].options) +'.\n')
    elif carTruck == 'car':
        print(f'Your vehicle is a {instances[b].color} {instances[b].make} {instances[b].model} {instances[b].numDoors} door with a {instances[b].engineSize} liter {instances[b].fuelType} engine.')  
        print(f'The options are ' + ", ".join(instances[b].options) +'.\n')
    b = b + 1




Output:
Are you entering a car or truck? car
please enter your license plate number: 123456
Please enter the vehicle make: ford
Please enter the vehicle model: mustang
Please enter the vehicle color: red
Please enter the vehicle fuel type: gas
Please enter your engine size in liters: 5
Please enter the number of doors: 2

Enter Y or N for the following options
Does your vehicle have a radio: y     
Does your vehicle have bluetooth: y
Does your vehicle have cruise control: y
Does your vehicle have power windows: y
Does your vehicle have power locks: y
Does your vehicle have power mirrors: y
Does your vehicle have remote start: y
Does your vehicle have a back up camera: y
Are you done adding vehicles (Y/N): n
Are you entering a car or truck? truck
please enter your license plate number: 789456
Please enter the vehicle make: chevy
Please enter the vehicle model: 1500
Please enter the vehicle color: black
Please enter the vehicle fuel type: gas
Please enter the cab style: crew cab
Please enter the bed length: 6

Enter Y or N for the following options
Does your vehicle have a radio: y
Does your vehicle have bluetooth: y
Does your vehicle have cruise control: y
Does your vehicle have power windows: y
Does your vehicle have power locks: y
Does your vehicle have power mirrors: y
Does your vehicle have remote start: y
Does your vehicle have a back up camera: y
Are you done adding vehicles (Y/N): y
Traceback (most recent call last):
  File "c:\Users\chris\Desktop\School\Intro to Programming\python_work\classes.py", line 138, in <module>
    print(f'Your vehicle is a {instances[b].color} {instances[b].make} {instances[b].model} {instances[b].cabStyle} and a {instances[b].bedLength} ft bed that runs on {instances[b].fuelType}.')
AttributeError: 'Car' object has no attribute 'cabStyle'
``

【问题讨论】：

标签： python list loops class

【解决方案1】：

在阅读答案之前，问问自己您从哪里获得您尝试打印的 carTruck 实例。

...

您指的是您添加的最后一个条目，而不是指当前实例！所以正确的方法是，例如。

b = 0
while b < len(instances):
    if isinstance(instances[b], Pickup): #CHANGED
        print(f'Your vehicle is a {instances[b].color} {instances[b].make} {instances[b].model} {instances[b].cabStyle} and a {instances[b].bedLength} ft bed that runs on {instances[b].fuelType}.')
        print(f'The options are ' + ", ".join(instances[b].options) +'.\n')
    elif isinstance(instances[b], Car): #CHANGED
        print(f'Your vehicle is a {instances[b].color} {instances[b].make} {instances[b].model} {instances[b].numDoors} door with a {instances[b].engineSize} liter {instances[b].fuelType} engine.')  
        print(f'The options are ' + ", ".join(instances[b].options) +'.\n')
    b = b + 1

我想补充两个建议...

第一个 - 此处不要使用 while 循环，例如使用 for。

for moving_thing in instances:
   if isinstance(moving_thing, Pickup):
       ...

2nd - 为每个类创建__str__ 方法，这样您就可以在不检查它是什么类型的车辆的情况下调用它。这里Dunder methods，比你打电话的更多

for moving_thing in instances:
    print(moving_thing)

【讨论】：

谢谢。这正是我所需要的。我可以说 carTruck 实例是问题所在，但无法弄清楚我需要什么。 isinstance 是我需要找到的功能。另外，感谢您提供更多见解。我还没有听说过 dunder 方法，我会研究它们。