使python用户定义的类可排序，hashable [英] Making a python user-defined class sortable, hashable

问题描述

当使用户定义的类在python中可排序和/或哈希时，需要重写/实现什么方法？

需要注意的是什么？ / p>

我输入 dir（{}）到我的解释器中获取内置dicts的方法列表。其中，我假设我需要实现一些子集

  ['__ cmp__'，'__eq__'，'__ge__' '__gt__'，'__hash__'，'__le__'，'__lt__'，'__ne__'] 
  

有什么区别，其中的方法必须实现Python3而不是Python2？

解决方案

我几乎发布了这个评论

为了使你的项目可排序，他们只需要实现 __ lt __ 。这是内置排序使用的唯一方法。

其他比较或 functools.total_ordering

为了使您的项目具有哈希值，您需要实现 __ hash __ 其他人指出。您还应以兼容方式实现 __ eq __ - 等效的项目应该散列相同。

What methods need to be overridden/implemented when making user-defined classes sortable and/or hashable in python?

What are the gotchas to watch out for?

I type dir({}) into my interpreter to get a list of methods on built-in dicts. Of those, I assume I need to some implement some subset of

['__cmp__', '__eq__', '__ge__', '__gt__', '__hash__', '__le__', '__lt__', '__ne__']

Is there a difference in which methods must be implemented for Python3 as opposed to Python2?

解决方案

I almost posted this as a comment to the other answers but it's really an answer in and of itself.

To make your items sortable, they only need to implement __lt__. That's the only method used by the built in sort.

The other comparisons or functools.total_ordering are only needed if you actually want to use the comparison operators with your class.

To make your items hashable, you implement __hash__ as others noted. You should also implement __eq__ in a compatible way -- items that are equivalent should hash the same.

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