使列表子类可哈希化 [英] Making a list subclass hashable

问题描述

我想从list派生一个类，为其添加一些实例属性，并使它可哈希化.有什么好方法(快速，整洁)?

I want to derive a class from list, add a few instance attributes to it, and make it hashable. What is a good (fast and neat) way to do it?

更新:

我删除了一个用例的冗长解释.我还将一个相关但独立的问题移至其他问题. /p>

I deleted a lengthy explanation of a use case. I also moved a related but separate issue into a different question.

推荐答案

这段代码很好.您正在复制列表，这可能会有点慢.

This code is fine. You're making a copy of the list, which could be a bit slow.

def __hash__(self):
    return hash(tuple(self.list_attribute))

如果想提高速度，可以有几种选择.

You have several options if you want to be faster.

• 将list_attribute存储为元组，而不是列表(完全构建后)
• 在 init 时刻计算一次哈希并存储哈希值.您可以这样做是因为您的类是不可变的，因此哈希永远不会改变.
• 编写您自己的哈希函数.这是元组的哈希函数，执行类似的操作.

• Store list_attribute as a tuple, not a list (after it is fully constructed)
• Compute the hash once at init time and store the hash value. You can do this because your class is immutable, so the hash will never change.
• Write your own hash function. Here's the hash function for tuple, do something similar.

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