如何在Python中继承和扩展列表对象？ [英] How to inherit and extend a list object in Python?

问题描述

我对使用python列表对象感兴趣，但功能稍有改动。特别是，我希望列表是1索引而不是0索引。例如：

I am interested in using the python list object, but with slightly altered functionality. In particular, I would like the list to be 1-indexed instead of 0-indexed. E.g.:

>> mylist = MyList()
>> mylist.extend([1,2,3,4,5])
>> print mylist[1]

输出应为：1

但当我更改 __ getitem __（）和 __ setitem __（）方法时，我得到了a RuntimeError：超出最大递归深度错误。我对这些方法进行了很多修改，但这基本上就是我在那里所做的：

But when I changed the __getitem__() and __setitem__() methods to do this, I was getting a RuntimeError: maximum recursion depth exceeded error. I tinkered around with these methods a lot but this is basically what I had in there:

class MyList(list):
    def __getitem__(self, key):
        return self[key-1]
    def __setitem__(self, key, item):
        self[key-1] = item

我想问题是 self [key-1] 它本身就是在调用它所定义的相同方法。如果是这样，我如何使用 list（）方法而不是 MyList（）方法？我尝试使用 super [key-1] 而不是 self [key-1] 但是这导致投诉 TypeError：'type'对象是unsubscriptable

I guess the problem is that self[key-1] is itself calling the same method it's defining. If so, how do I make it use the list() method instead of the MyList() method? I tried using super[key-1] instead of self[key-1] but that resulted in the complaint TypeError: 'type' object is unsubscriptable

有什么想法吗？另外，如果你能指出一个很好的教程，那就太棒了！

Any ideas? Also if you could point me at a good tutorial for this that'd be great!

谢谢！

推荐答案

使用 super（）函数调用基类的方法，或直接调用该方法：

Use the super() function to call the method of the base class, or invoke the method directly:

class MyList(list):
    def __getitem__(self, key):
        return list.__getitem__(self, key-1)

或

class MyList(list):
    def __getitem__(self, key):
        return super(MyList, self).__getitem__(key-1)

但是，这不会改变其他列表方法的行为。例如，索引保持不变，这可能导致意外结果：

However, this will not change the behavior of other list methods. For example, index remains unchanged, which can lead to unexpected results:

numbers = MyList()
numbers.append("one")
numbers.append("two")

print numbers.index('one')
>>> 1

print numbers[numbers.index('one')]
>>> 'two'

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