内部字典订单可以改变吗？ [英] Can internal dictionary order change?

问题描述

exampleDict = {'a':1, 'b':2, 'c':3, 'd':4}

上述字典最初以此顺序迭代：

The above dictionary initially iterated through in this order:

b=2
d=4
a=1
c=3

然后，我在代码中移动了大量的文件，现在它按照这个顺序遍历：

Then, I moved around a ton of files in my code, and now it iterates through in this order:

d=4
a=1
c=3
b=2

我知道该订单内部存储为一个hashmap，但是会导致内部订单更改？

I know that the order is internally stored as a hashmap, but what would cause that internal order to change?

编辑：我不需要保留订单，所以我会坚持使用dict。我只是想知道为什么会发生。我认为订单不能保证，但是一旦它有任意的内部订单，它会坚持使用它来进行以后的迭代。

I don't need to preserve order so I will stick with using a dict. I am just wondering why it happened. I thought order wasn't guaranteed, but once it has its arbitrary internal order, it sticks with it for future iterations.

推荐答案

Dict没有固定的订单，从文档

Dict don't have a fixed order, from documentation

CPython实现细节：键和值以
任意顺序列出，这是非随机的，因Python而异
实现，并且取决于字典的插入历史
和删除。

CPython implementation detail: Keys and values are listed in an arbitrary order which is non-random, varies across Python implementations, and depends on the dictionary’s history of insertions and deletions.

如果你真的需要保留它的排序，那里是一个名为 OrderedDict 的对象：

If you really need to keep it ordered, there is an object called OrderedDict :

from collections import OrderedDict
exampleDict = OrderedDict({'a':1, 'b':2, 'c':3, 'd':4})

另请参阅OrderedDict文档 here

see also OrderedDict documentation here

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