实例化Python对象和使用列表

Question

我是编程和尝试自学的新手.我目前正在尝试学习如何从类构建对象,我想我理解.我当前的任务是将对象添加到列表中并打印该列表.最终,我正在尝试构建一个创建对象的程序,并列出已在编号列表中创建的每个对象,即:

1 - tomato, red
2 - corn, yellow
etc...

首先,我只是想构建这个的基本部分.这是我做的:

# Builds objects on instantiation for a vegetable and color
class Veg:
    def __init__(self, name, color):
        self.name = name
        self.color = color
        print('You have created a new', self.color, self.name, end='.\n')

# Function to create a new vegetable and store it in a list
def createVeg():
    name = input('What is the name of the Vegetable? ')
    color = input('What color is the vegetable? ')
    Veg(name, color)
    vegList.append(Veg)
    return

# Initialize variables
vegList = []
choice = 'y'

# Main loop
while choice == 'y':
    print('Your basket contains:\n', vegList)
    choice = input('Would you like to add a new vegetable? (y / n) ')
    if choice == 'y':
        createVeg()
    if choice == 'n':
        break

print('Goodbye!')

当我运行它时,我得到以下内容:

Your basket contains:
 []
Would you like to add a new vegetable? (y / n) y
What is the name of the Vegetable? tomato
What color is the vegetable? red
You have created a new red tomato.
Your basket contains:
 [<class '__main__.Veg'>]
Would you like to add a new vegetable? (y / n) y
What is the name of the Vegetable? corn
What color is the vegetable? yellow
You have created a new yellow corn.
Your basket contains:
 [<class '__main__.Veg'>, <class '__main__.Veg'>]
Would you like to add a new vegetable? (y / n) n
Goodbye!

所以,据我所知,一切都有效,除了打印清单,我无法弄清楚.它似乎是附加列表属性,但不显示对象.我也试过'for'循环,但结果相同.

Answer 1

这一切都按设计工作.该<class '__main__.Veg'>字符串是表示你的Veg类的实例.

您可以通过为类提供__repr__方法来自定义该表示:

class Veg:
    # ....

    def __repr__(self):
        return 'Veg({!r}, {!r})'.format(self.name, self.color)

所有__repr__功能都要返回一个合适的字符串.

使用上面的示例__repr__函数,您的列表将显示为:

[Veg('tomato', 'red'), Veg('corn', 'yellow')]

您确实需要确保实际附加新实例.代替:

Veg(name, color)
vegList.append(Veg)

做这个:

newveg = Veg(name, color)
vegList.append(newveg)