python 3.7 中的无序字典

Question

Dictionaries in python are ordered since Python 3.6

From - https://stackoverflow.com/a/39980744/4647107

Are dictionaries ordered in Python 3.6+?

They are insertion ordered. As of Python 3.6, for the CPython implementation of Python, dictionaries remember the order of items inserted. This is considered an implementation detail in Python 3.6; you need to use OrderedDict if you want insertion ordering that's guaranteed across other implementations of Python.

As of Python 3.7, this is no longer an implementation detail and instead becomes a language feature. From a python-dev message by GvR:

Make it so. "Dict keeps insertion order" is the ruling. Thanks!

This simply means that you can depend on it. Other implementations of Python must also offer an insertion ordered dictionary if they wish to be a conforming implementation of Python 3.7.

Is there a way to implement an unordered dictionary in python now?

Answer 1

You can fake it:

>>> import random
>>> d={'a':[1,2,3],'b':[4,5,6],'c':[7,8,9]}
>>> items=list(d.items())
>>> random.shuffle(items)
>>> dict(items)
{'c': [7, 8, 9], 'b': [4, 5, 6], 'a': [1, 2, 3]}
>>> 

Answer 2

As a few people have mentioned it would help to understand why you would like an unordered dict. Personally I was looking for an unordered dict because I was working with OrderedDicts, and their behavior meant that I couldn't directly compare them using == . For example:

In [1]: from collections import OrderedDict
In [2]: dict_1 = OrderedDict([('a', 0), ('b', 1), ('c', 2)])
In [3]: dict_2 = OrderedDict([('c', 2), ('b', 1), ('a', 0)])
In [4]: dict_1 == dict_2
Out[4]: False

A simple solution to this is to turn the OrderedDict back into a dict.

In [5]: dict(dict_1) == dict(dict_2)
Out[5]: True

Answer 3

Might be too late to answer but here's what I used,

class UnorderedDict:
    def __setitem__(self, key, value):
        setattr(self, key, value)
    def __getitem__(self, key):
        return getattr(self, key)
test = UnorderedDict()
test["key"] = "yay"
print(test["key"])

It sets and gets attribute, this doesn't have any order afaik.