csv.DictReader can return basic dict instead of OrderedDict

[selik]

BPO	34003
Nosy	@rhettinger, @ericvsmith, @merwok, @selik, @miss-islington
PRs	bpo-34003: Use dict instead of OrderedDict in csv.DictReader #8014 bpo-34003: Re-add versionchanged entry in csv docs #20657 [3.9] bpo-34003: Re-add versionchanged entry in csv docs (GH-20657) #20770 [3.8] bpo-34003: Re-add versionchanged entry in csv docs (GH-20657) #20771

^{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 2019-02-01.03:02:05.039>
created_at = <Date 2018-06-29.19:47:39.124>
labels = ['3.8', 'library', 'performance']
title = 'csv.DictReader can return basic dict instead of OrderedDict'
updated_at = <Date 2020-06-10.01:26:39.737>
user = 'https://github.com/selik'

bugs.python.org fields:

activity = <Date 2020-06-10.01:26:39.737>
actor = 'miss-islington'
assignee = 'none'
closed = True
closed_date = <Date 2019-02-01.03:02:05.039>
closer = 'rhettinger'
components = ['Library (Lib)']
creation = <Date 2018-06-29.19:47:39.124>
creator = 'selik'
dependencies = []
files = []
hgrepos = []
issue_num = 34003
keywords = ['patch']
message_count = 9.0
messages = ['320734', '320735', '320739', '320741', '320748', '334613', '371148', '371151', '371152']
nosy_count = 5.0
nosy_names = ['rhettinger', 'eric.smith', 'eric.araujo', 'selik', 'miss-islington']
pr_nums = ['8014', '20657', '20770', '20771']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue34003'
versions = ['Python 3.8']

[selik]

Since dicts are now keeping insertion order as of 3.7, we can switch to the more efficient construction of dict rather than OrderedDict for each row in the CSV file.

[selik]

Pull request.

#8014

[ericvsmith]

The dict and OrderedDict APIs are slightly different, although I'm not sure anyone cares. See bpo-32339. In that PR #4904, Guido said to not make this change. See also the python-dev discussion at https://mail.python.org/pipermail/python-dev/2017-December/151351.html

If you feel strongly about this, I suggest discussing it on python-dev first.

[selik]

I searched for previously submitted issues, but somehow didn't spot bpo-32339.

I'll do some searching for whether anyone uses move_to_end on DictReader rows and respond to the mailing list with a report.

[rhettinger]

This might need a deprecation before switching but it would be useful. The DictReader can produced huge numbers of instances that would benefit from the smaller size.

[rhettinger]

New changeset 9f3f093 by Raymond Hettinger (Michael Selik) in branch 'master':
bpo-34003: Use dict instead of OrderedDict in csv.DictReader (GH-8014)
9f3f093

[miss-islington]

New changeset 7aed052 by Éric Araujo in branch 'master':
bpo-34003: Re-add versionchanged entry in csv docs (GH-20657)
7aed052

[miss-islington]

New changeset 663836e by Miss Islington (bot) in branch '3.8':
[3.8] bpo-34003: Re-add versionchanged entry in csv docs (GH-20657) (GH-20771)
663836e

[miss-islington]

New changeset 73b728a by Miss Islington (bot) in branch '3.9':
[3.9] bpo-34003: Re-add versionchanged entry in csv docs (GH-20657) (GH-20770)
73b728a