在单独的文件中从类创建对象 [英] Create object from class in separate file

问题描述

我已经完成了一些关于Python的教程，并且我知道如何定义类，但是我不知道如何使用它们.例如，我创建以下文件(car.py):

I have done several tutorials on Python and I know how to define classes, but I don't know how to use them. For example I create the following file (car.py):

class Car(object):
    condition = 'New'
    def __init__(self,brand,model,color):
        self.brand = brand
        self.model = model
        self.color = color

    def drive(self):
        self.condition = 'Used'

然后，我创建另一个文件(Mercedes.py)，在该文件中，我想从Car类创建对象Mercedes:

Then I create another file (Mercedes.py), where I want to create an object Mercedes from the class Car:

Mercedes = Car('Mercedes', 'S Class', 'Red')

，但出现错误:

NameError: name 'Car' is not defined

如果我在创建实例(对象)的同一文件中创建实例(对象)，则没有问题:

If I create an instance (object) in the same file where I created it (car), I have no problems:

class Car(object):
    condition = 'New'
    def __init__(self,brand,model,color):
        self.brand = brand
        self.model = model
        self.color = color

    def drive(self):
        self.condition = 'Used'

Mercedes = Car('Mercedes', 'S Class', 'Red')

print (Mercedes.color)

哪些印刷品:

Red

所以问题是:如何从同一包(文件夹)中不同文件的类创建对象?

So the question is: How can I create an object from a class from different file in the same package (folder)?

推荐答案

在您的Mercedes.py中，您应该按以下方式导入car.py文件(只要两个文件位于相同目录中):

In your Mercedes.py, you should import the car.py file as follows (as long as the two files are in the same directory):

import car

然后您可以执行以下操作:

Then you can do:

Mercedes = car.Car('Mercedes', 'S Class', 'Red')  #note the necessary 'car.'

或者，你可以做

from car import Car

Mercedes = Car('Mercedes', 'S Class', 'Red')      #no need of 'car.' anymore

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