strptime %d handling of single digit day of month

[mikegleen]

BPO	34903
Nosy	@brettcannon, @matrixise, @pganssle, @miss-islington, @tirkarthi, @mikegleen
PRs	bpo-34903: For datetime.datetime.strptime(), the leading zero for some two-digit formats is optional #9747 bpo-34903: For datetime.datetime.strptime(), the leading zero for some two-digit formats is optional. #14149 [3.7] bpo-34903: Document that some strptime formats only require 1 digit (GH-14149) #14205 [3.8] bpo-34903: Document that some strptime formats only require 1 digit (GH-14149) #14206

^{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 2019-06-18.18:56:50.324>
created_at = <Date 2018-10-05.07:31:26.590>
labels = ['type-bug', '3.8', 'docs']
title = 'strptime %d handling of single digit day of month'
updated_at = <Date 2021-05-14.19:50:35.336>
user = 'https://github.com/mikegleen'

bugs.python.org fields:

activity = <Date 2021-05-14.19:50:35.336>
actor = 'guziy.sasha'
assignee = 'docs@python'
closed = True
closed_date = <Date 2019-06-18.18:56:50.324>
closer = 'p-ganssle'
components = ['Documentation']
creation = <Date 2018-10-05.07:31:26.590>
creator = 'Mike Gleen'
dependencies = []
files = []
hgrepos = []
issue_num = 34903
keywords = ['patch']
message_count = 11.0
messages = ['327109', '327110', '327156', '327200', '327227', '327237', '346000', '346001', '346002', '346004', '393688']
nosy_count = 8.0
nosy_names = ['brett.cannon', 'docs@python', 'matrixise', 'p-ganssle', 'miss-islington', 'xtreak', 'Mike Gleen', 'guziy.sasha']
pr_nums = ['9747', '14149', '14205', '14206']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34903'
versions = ['Python 3.8']

[mikegleen]

strptime correctly parses single digit day-of-month values (at least in the case of "%d %b %Y") which is the behavior I want. However, the documentation seems to say that the field must be two digits with a leading zero if necessary. So I hope that this is the intended behavior rather than just an accidental artifact. If so, then my suggestion is that the documentation be updated to reflect this.

[matrixise]

Hi Mike,

Thank you for your issue, but could you add the link to the documentation, just because we have time.strptime and datetime.datetime.strptime.

Thank you,

[mikegleen]

Sorry for the omission. This refers to datetime.datetime.strptime. The documentation I referenced is: https://docs.python.org/3/library/datetime.html; I did not test 2.7.

[brettcannon]

So the documentation reads that way because it was originally written for strftime and has been repurposed to represent both. If the code does the right thing then adding a note that strptime supports single digits accurately would probably be a welcome pull request!

[tirkarthi]

In addition to %d there are also other items that support single digit though zero padding is mentioned with strptime as below in the context of strftime :

>>> import datetime
>>> datetime.datetime.strptime("1/1/2018 1:1:1", "%d/%m/%Y %I:%M:%S")
datetime.datetime(2018, 1, 1, 1, 1, 1)


>>> datetime.datetime.strftime(datetime.datetime(year=2018, month=1, day=1, hour=1, second=1, minute=1), "%d/%m/%Y %I:%M:%S")
'01/01/2018 01:01:01'

I couldn't find exact set of words that can be used to denote that zero padding is optional in strptime and it's returned as zero padded in strftime but if we are changing %d then I propose changing other items too with similar wording.

Thanks

[mikegleen]

Thanks for the quick response. I would be happy to write a pull request for
the doc change. I've never done this before so it'll take a little while to
get my head around the process, but the "Helping with Documentation"
chapter seems good.

Mike

On Sat, Oct 6, 2018 at 7:09 AM Karthikeyan Singaravelan <
report@bugs.python.org> wrote:

Karthikeyan Singaravelan <tir.karthi@gmail.com> added the comment:

In addition to %d there are also other items that support single digit
though zero padding is mentioned with strptime as below in the context of
strftime :

>>> import datetime
>>> datetime.datetime.strptime("1/1/2018 1:1:1", "%d/%m/%Y %I:%M:%S")
datetime.datetime(2018, 1, 1, 1, 1, 1)

>>> datetime.datetime.strftime(datetime.datetime(year=2018, month=1,
day=1, hour=1, second=1, minute=1), "%d/%m/%Y %I:%M:%S")
'01/01/2018 01:01:01'

I couldn't find exact set of words that can be used to denote that zero
padding is optional in strptime and it's returned as zero padded in
strftime but if we are changing %d then I propose changing other items too
with similar wording.

Thanks

----------
nosy: +xtreak

---

Python tracker <report@bugs.python.org>
<https://bugs.python.org/issue34903\>

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[pganssle]

New changeset 6b9c204 by Paul Ganssle (Mike Gleen) in branch 'master':
bpo-34903: Document that some strptime formats only require 1 digit (GH-14149)
6b9c204

[miss-islington]

New changeset 452b417 by Miss Islington (bot) in branch '3.7':
bpo-34903: Document that some strptime formats only require 1 digit (GH-14149)
452b417

[pganssle]

Thanks for the PR, Mike! This is now merged and backported to Python 3.7, so I believe we can close this issue.

[miss-islington]

New changeset 35aa0b0 by Miss Islington (bot) in branch '3.8':
bpo-34903: Document that some strptime formats only require 1 digit (GH-14149)
35aa0b0

[guziysasha]

This is a bit unfortunate for the formats without separators, that could give wrong results silently:

In [26]: datetime.strptime("2020010112", "%Y%m%d%H")
Out[26]: datetime.datetime(2020, 1, 1, 12, 0)

In [27]: datetime.strptime("2020010112", "%Y%m%d%H%M")
Out[27]: datetime.datetime(2020, 1, 1, 1, 2)