True 和 1 和 1.0 在 python 字典中被评估为相同

问题描述

谁能解释一下python字典的这种行为?

Can anyone explain this behaviour of python dictionaries?

d = {}
d[True] = 'Magic'
d[1] = 'Cool'
d[1.0] = 'Hello'
print(d)

# {True: 'Hello'}

为什么它不打印所有其他(键、值)对?

Why does it not print all the other (key, value) pairs?

为什么 True、1 和 1.0 被评估为相同?

Why does True, 1 and 1.0 is evaluated to be the same?

推荐答案

hash 3 项 1, 1.0, True 相同(等于 1).如果没有冲突，这就是 python 用作字典键的内容.并且由于 1 == 1.0 == True 也是 True 没有冲突.

the hash of the 3 items 1, 1.0, True is the same (it equals 1). that's what python uses as the key for dictionaries if there are no collisions. and as 1 == 1.0 == True is also True there are no collisions.

这里有更多关于python 旧实现的详细信息字典.新的实现按照这些思路做事(但保留了顺序).

here are more details about the old implementation of python dictionaries. the new implementation does things along those lines (but preserves the order).

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