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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