如何在Python中创建可排序的数据类型? [英] how to make sortable datatype in Python?

问题描述

我有一堂课，代表一些领域.当对此类的实例列表进行排序时，我希望它们以特定的顺序进行排序(从每个实例中获取特定的键).我可以做list.sort(key=Classname.sortKey)并定义一个sortKey方法，但是我宁愿去做list.sort()并解决它.我认为我可以通过覆盖__cmp__来做到这一点.但是，当我与非数据类型的东西进行比较时该怎么办?我想像...

I have a class representing something with a few fields. When a list of instances of this class is sorted, I want them to be sorted in a particular order (get a particular key from each one). I can just do list.sort(key=Classname.sortKey) and define a sortKey method, but I'd rather just do list.sort() and have it work out. I figure I can do this by overriding __cmp__. However, what do I do when I'm comparing with something that is not my data type? I figure something like...

def __cmp__(self, o):
    if isinstance(o, MyClass):
        return cmp(self.sortKey(), o.sortKey())
    return object.__cmp__(self, o) ##**wrong

但是可以代替.我不在乎它们在异构列表中采用什么顺序.我只返回0，但是对于任何x而不是MyClass的实例，像MyClass(...) == x这样的东西总是正确的.

but that works instead. I don't care what ordering they take in a heterogeneous list. I would just return 0 but then stuff like MyClass(...) == x is always true, for any x not an instance of MyClass.

推荐答案

查看 http://wiki.python.org/moin/HowTo/Sorting/

您要在类中覆盖__lt__以便使内置的sort函数按您所描述的方式工作.

You want to override __lt__ in your class for the built in sort function to work the way you described.

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