Update language reference to specify that dict is insertion-ordered.

[ericsnowcurrently]

BPO	39879
Nosy	@vstinner, @ericsnowcurrently, @zware, @Mariatta, @miss-islington, @furkanonder, @AkechiShiro
PRs	bpo-39879: Update docs dict preserve insertion order #19006 bpo-39879: update language reference to specify that dict is insertion-ordered. #19027 [3.8] bpo-39879: Update datamodel docs to include dict ordering (GH-19006) #19173 [3.7] bpo-39879: Update datamodel docs to include dict ordering (GH-19006) #19174

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-03-26.15:01:56.496>
created_at = <Date 2020-03-06.18:33:48.298>
labels = ['easy', '3.7', '3.8', '3.9', 'docs']
title = 'Update language reference to specify that dict is insertion-ordered.'
updated_at = <Date 2020-03-26.15:19:26.333>
user = 'https://github.com/ericsnowcurrently'

bugs.python.org fields:

activity = <Date 2020-03-26.15:19:26.333>
actor = 'vstinner'
assignee = 'docs@python'
closed = True
closed_date = <Date 2020-03-26.15:01:56.496>
closer = 'zach.ware'
components = ['Documentation']
creation = <Date 2020-03-06.18:33:48.298>
creator = 'eric.snow'
dependencies = []
files = []
hgrepos = []
issue_num = 39879
keywords = ['patch', 'easy']
message_count = 14.0
messages = ['363533', '364204', '364206', '364229', '364303', '364484', '364494', '364502', '364520', '365080', '365081', '365082', '365083', '365085']
nosy_count = 8.0
nosy_names = ['vstinner', 'docs@python', 'eric.snow', 'zach.ware', 'Mariatta', 'miss-islington', 'furkanonder', 'AkechiShiro']
pr_nums = ['19006', '19027', '19173', '19174']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue39879'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[ericsnowcurrently]

As of 3.7 [1], dict is guaranteed to preserve insertion order:

the insertion-order preservation nature of dict
objects has been declared to be an official part
of the Python language spec.

However, at least one key part of the language reference [2] was not updated to reflect this: "3.2. The standard type hierarchy" > "Mappings" > "Dictionaries".

Note that the library docs [3] *were* updated.

[1] https://docs.python.org/3/whatsnew/3.7.html#summary-release-highlights
[2] https://docs.python.org/3/reference/datamodel.html#index-30
[3] https://docs.python.org/3/library/stdtypes.html#typesmapping

[AkechiShiro]

Hi,

I would like to take this issue as my first contribution to Python, I'm currently subscribed to the python-core-mentorship list.
I do not know exactly how to submit a patch for an issue.

Kind regards.

[Mariatta]

Patch are submitted as pull request on our GitHub repo.
Here's a write-up on how to do it
https://devguide.python.org/pullrequest/#step-by-step-guide

[AkechiShiro]

Following the guide, I've send a patch with the fix, I'm waiting for a review. Once the patch will be reviewed and accepted. My patch will need to be backported from 3.9 to 3.7.

[furkanonder]

I sent pr. All tests passed successfully. If accepted, this will be my first contribution :)
#19027

[zware]

Hi Furkan. Please note that Lahfa Samy had already submitted a PR for this issue after "claiming" it with a note here; proper "netiquette" suggests not jumping in with your own PR in such a situation.

Fortuitously though, it looks like the both of you have actually implemented about half of the final change that we need here :). I'll be leaving review comments on both PRs; I recommend that the two of you work together to combine your PRs into a single PR with both of your (revised) changes.

[AkechiShiro]

Hi Furkan, would you mind to combine your revised PR with mine so that we can do as suggested by Zachary?

[furkanonder]

Hello Samy,
I sent you pr from the docs-dict-ordered branch in your cpython repository. Now both of us have merged pr. I closed my own pr. You can also close your pr and send these changes again as bpo-39879.

It's my pr,AkechiShiro#1

[AkechiShiro]

Thank you for your quick work, I have successfully merged your changes in the branch of the first PR, now awaiting review from Zachary.

[zware]

New changeset 59c644e by Lahfa Samy in branch 'master':
bpo-39879: Update datamodel docs to include dict ordering (GH-19006)
59c644e

[miss-islington]

New changeset ea0eeb8 by Miss Islington (bot) in branch '3.7':
bpo-39879: Update datamodel docs to include dict ordering (GH-19006)
ea0eeb8

[miss-islington]

New changeset 96686c7 by Miss Islington (bot) in branch '3.8':
bpo-39879: Update datamodel docs to include dict ordering (GH-19006)
96686c7

[zware]

Thanks for the patch!

[vstinner]

What's New in Python 3.7 says:

the insertion-order preservation nature of dict objects has been declared to be an official part of the Python language spec.

Reference: https://mail.python.org/pipermail/python-dev/2017-December/151283.html

I just wanted to add a reference for this change. I wanted to check if it is ok to modify the doc: yes, it is :-)