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Comment by BiteCode_dev | Hacker News Reader

I live in the Python bubble, so I haven't realized until this post that so few people knew about that.

This post is massively popular despite talking about a feature we had since Python 3.6, in 2016, that was posted on HN at the time and that is featured in most popular tutorials.

A good reminder that most of the world doesn't revolve about my favorite language. And that information is not that fast to spread.

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> about a feature we had since Python 3.6, in 2016

No, you had that feature in one implementation. Now it's in the language specification. That's vastly different because only now you can rely on it without fearing it can go away with the next release.

First, cPython is 99% of Python deployments. So much that if a script works on it but not on another implementation, people often consider the later broken.

As this post proves that most people don't even know about this feature, you can be pretty sure the vast majority of people don't know about pypy, micropython, etc.

Secondly, even if you want to nit pick, Python 3.7 made it official more than one year ago. We are currently in the 3.9 alpha.

In fact, 3.7 didn't touch the implementation, just merely declared "yep, good idea, let's keep it that way".

There's also the indication that this is official, and not just an implementation quirk. I still used OrderedDict in 3.6 because there was no guarantee 3.7 (or later) wouldn't silently break ordering on the standard dict. At least now it's unlikely to change because it will be considered a breaking change.

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. Pypy even before that.

A barely legible email dump with 50 concurrent answers is supposed to be the clear official statement?

Not to mention that developers just begin migrating to python 3 in 2017 and code still had to work on 2.7 that doesn't order.

I knew about it, because everyone was talking about it. The origination of the actual information is irrelevant. It was basically interesting gossip for a few weeks.

The official release notes for the following release is certainly a clear official statement.

https://www.python.org/downloads/release/python-370/

“The insertion-order preservation nature of dict objects is now an official part of the Python language spec.” (June 27, 2018)

The ruling is the very first and only line from the link:

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

There's a great talk by David Beazley[0], which I don't remember its title right now, where he bashes all previous python versions except the latest at the time[1], which was 3.6. And he says "since I'm not a core developer, I can tell you this: rely on dicts being ordered so much that eventually they'll make it official". Guess he "won" in the end ;)

[0] Well, he usually gives great talks anyway

[1] Alright, he literally started many talks doing that

Yes, David Beazley's talks are always wonderful!

Raymond Hettinger does or did a few talks on dictionaries too. He covers the history of dictionaries in python and how they evolved. It was mentioned in the article's comment section.

https://www.youtube.com/watch?v=p33CVV29OG8

Whoa, calm your horses angry boy.

There is no language spec for Python, the CPython implementation defines the language.

The language reference is a specification for the language. The library reference is a specification for the standard library.

https://docs.python.org/3/reference/index.html

That still was announced a while ago. When reading the title I though it was something new (maybe now Python decided to keep the keys sorted? ;)

> rely on it without fearing it can go away with the next release

This is Python we're talking about.

I have lived in Python ~80% of my career (~50% now) currently), although a large chunk of my career was writing 2.7 compatible with 2.6 (thanks RHEL). For the last year and a half I have written 3.6+ exclusively and I didn't realize that regular dicts were now ordered.

I don't use dicts if I require ordering, but if I did I would probably still reach for collections.OrderedDict...

I wonder what the implications are of dict ordering with the "new" (new for me...) function args and *kwargs...from the hip it sounds pretty handy.

The implications are that now you get to see the order in which keyword args were specified by the caller. And in classes, you get to see the order in which attributes were defined. Both can come in very handy.

Dict ordering started from the need to have class attributes, args and kwargs ordered if I recall.

No, that was a happy coincidence. The goal of the dict implementation was efficiency. Ordering was a side-effect.

Most of the python I've written and maintain (which, honestly, isn't too much) was 2.7, so it is news to me too. Nice!

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