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- 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 (and other ordered behavior).
stackoverflow.com/questions/39980323/are-dictionaries-ordered-in-python-3-6
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Does CPython maintain insertion order?
What is insertion order in Python?
Do Python dictionaries remember the Order of items inserted?
What is Dictionary iteration order in CPython?
Oct 11, 2016 · Dictionaries are insertion ordered as of Python 3.6. It is described as a CPython implementation detail rather than a language feature. The documentation states: dict () now uses a “compact” representation pioneered by PyPy. The memory usage of the new dict () is between 20% and 25% smaller compared to Python 3.5.
CPython 3.6 maintains insertion order under most circumstances as an implementation detail. Starting from Python3.7 onward, it has been declared that implementations MUST maintain insertion order to be compliant.
Jun 20, 2024 · Yes, as of Python 3.7, dictionaries are ordered. This means that when you iterate over a dictionary, insert items, or view the contents of a dictionary, the elements will be returned in the order in which they were added.
- How and Why
- Dict[Int] vs. List
- Not Sets though!
A plain hash table holds both keys and values in a pseudo random order determined by hashes calculated from keys. It is also sparse, with unoccupied holes in a pre-allocated array: Since version 3.6 CPython holds keys and values in a separate dense array, while the hash table itself only holds indexesinto that: Since the entries array is populated ...
Does it mean that a dict with int keys is the same as list? There's still a few practical differences. One obvious difference is the API. You'd have to always mention indexes explicitly when working with a dict[int], there's no such thing as .append(value) or .pop()with no argument. Frankly, I can't see any point in trying to make it work :-) Also,...
Yep, to my surprise sets are still unordered: Until this moment I thought of sets as basically thin wrappers around actual dicts operating on their keys and neglecting values. Turns out, they have their own implementation.
The short answer is that while insertion order of regular dicts is maintained, deletes are allowed to rearrange keys arbitrarily, and there is no way to rearrange keys in place. OrderedDict doesn't have those restrictions, but it's implementation uses more memory, so using it everywhere (since every object without __slots__ is backed by a dict ...
Feb 8, 2020 · BDFL declared Python dict to be ordered in 2017 — It can't be more official than that for Python https://mail.python.org/pipermail/python-dev/2017-December/1... i.e., Python 3.7 (whatever implementation must keep the insertion order). CPython keeps the order since Python 3.6.
Changed in version 3.7: Dictionary order is guaranteed to be insertion order. This behavior was implementation detail of CPython from 3.6. list(d) on a dictionary returns a list of all the keys used in the dictionary, in insertion order.
