Python 设置 1 和 True 的重复 [英] Python set interpetation of 1 and True

问题描述

在 IPython 3 交互式 shell 中:

In IPython 3 interactive shell:

In [53]: set2 = {1, 2, True, "hello"}

In [54]: len(set2)
Out[54]: 3

In [55]: set2
Out[55]: {'hello', True, 2}

这是不是因为 1 和 True 得到相同的解释，所以鉴于该集合消除了重复项，只有其中一个(True)可以保留?我们如何才能同时保留两者?

Is that because 1 and True get the same interpetation so given that set eliminates duplicates, only one of them (True) gets to stay? How can we keep both?

推荐答案

集合是 哈希.即使语句 1 is True 是 False，语句 1 == True 也是 True.因此，它们具有相同的哈希值并且不能单独存在于一个集合中，并且您不能将它们都保存在一个集合中

A set is a collection of hashables. Even though the statement 1 is True is False, the statement 1 == True is True. Because of that, they have the same hash value and cannot exist separately in a set, and you cannot keep them both in a set

EDIT 明确地说，正如 jme 所指出的，这是因为两件事都是正确的 - 它们是相等的(根据 __eq__)并且它们具有相同的 哈希值(根据__hash__).

EDIT To make it explicit, as jme pointed out, it is because BOTH things are true - they are equal (per __eq__) AND they have the same hash value (per __hash__).

在一个完美的世界中，相等的对象也将具有相同的哈希值，幸运的是，对于内置类型也是如此.

In a perfect world, equal objects would also have the same hash value, and thankfully this is true for built-in types.

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