gh-140715: Add %t and %n format codes support to strptime() by jyalim · Pull Request #144896 · python/cpython

jyalim · 2026-02-17T03:38:54Z

Incrementally builds C99+ datetime support with addition of %t and %n with two lines of code. Also adds tests and updates documentation.

Continued effort from PR: #140647 , #144819.

Documentation drops (0) footnote.

Passed all tests.

Passed patchcheck.

Issue: #140715

Issue: Update str*time to C11 format codes #140715

Note, this PR originally only was for %t; %n was added 2026-02-25.

📚 Documentation preview 📚: https://cpython-previews--144896.org.readthedocs.build/

StanFromIreland

This is quite an odd case, as per the standard for strftime, it is a \t character, however, for strptime():

A series of conversion specifications composed of %n, %t, white-space bytes, or any combination is executed by scanning up to the first non-white-space byte (which remains unscanned), or until no more characters can be scanned.

And, more straightforward:

Arbitrary whitespace.

Considering that this is the wide-spread behaviour, it should instead be r'\s+' for %n/%t (with additional tests), and add a note to the doc.

jyalim · 2026-02-21T07:33:49Z

Thanks, this was a great catch that adds some power to %t for strptime. I've implemented the changes!

jyalim · 2026-02-22T22:55:53Z

Thank you, the documentation changes were implemented.

StanFromIreland

We could also do \n now, since it is equivalent. (re-use the tests please)

typo fix Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

remove trailing whitespace Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

jyalim · 2026-02-26T06:17:55Z

Thanks! All the requested changes were implemented. The title and description of this PR were also updated to include %n.

jyalim · 2026-02-28T22:56:10Z

Thank you, the tests have been merged and all requested changes have been implemented.

clarify "arbitrary" with "zero or more" Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

…wmcM_.rst Drop quotes around format directives Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

StanFromIreland · 2026-03-01T19:06:15Z

Something broke with the CI, I'll try updating the branch.

jyalim · 2026-03-01T22:15:57Z

Thanks! Changes have been made.

StanFromIreland

LGTM

encukou · 2026-03-03T12:02:11Z


+ def test_strptime_n_and_t_format(self):
+ whitespaces = ('', ' ', '\t', '\r', '\v', '\n', '\f')
+ for fd in ('n', 't'):


Would it make sense to also test '%n%t' and the non-empty whitespaces as part of the pattern?

Would it make sense to add whitespace to the table in the docs? (It already worked before, but AFAIK wasn't documented/tested.)

Commit d6ca685 added '%n%t' and '%t%n'.
The final test for each whitespace format directive is ' \t\r\v\n\f', due to the ''.join(whitespaces) argument in the loop. Did you have another non-empty whitespace pattern in mind?
I'm all for improved documentation, could you clarify what you are envisioning? The whitespace format directives (%n and %t) are specified in the format directive table.

(By pattern I meant fd; thanks for doing that change!)
In docs, I meant adding entries for space and tab, in addition to the percent directives, to document that strptime “collapses” runs of whitespace kand %t/%n.

PEP 8 fix on existing code Co-authored-by: Petr Viktorin <encukou@gmail.com>

PEP 8 comma for exploded function arguments Co-authored-by: Petr Viktorin <encukou@gmail.com>

…lso add PEP 8 trailing commas to all exploded function arguments

… day (01)

encukou · 2026-03-13T13:00:18Z

The remaining doc update can be done in a separate PR.

…thonGH-144896) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

jyalim added 3 commits February 16, 2026 20:32

add %t C99 token to strptime
43c8345

init passing tests
d838236

drop (0) footnote from %t docs, reflecting support; add support note
a31ad12

jyalim requested review from abalkin and pganssle as code owners February 17, 2026 03:38

bedevere-appBot added the awaiting review label Feb 17, 2026

bedevere-appBot mentioned this pull request Feb 17, 2026
Update str*time to C11 format codes #140715
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5 tasks

blurb-itBotand others added 2 commits February 17, 2026 03:43

📜🤖 Added by blurb_it.
669870a

add support note
d77ebf7

StanFromIreland self-assigned this Feb 17, 2026

StanFromIreland reviewed Feb 18, 2026
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Comment threadLib/test/datetimetester.py Outdated

jyalim added 5 commits February 20, 2026 22:32

modify %t -> more general r'\s+' from '\t' to meet C99
fcc03cf

use theclass() and test '\s+' functionality, as requested
5193157

test '\s+' functionality, as requested
edfed51

alphabetize 3.15 patch notes
16195db

update docs to reflect powerful %t strptime functionality
7301962

StanFromIreland reviewed Feb 21, 2026
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Comment threadDoc/library/datetime.rst Outdated

simplify docs, as requested
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Comment threadLib/_strptime.py Outdated
Comment threadLib/test/datetimetester.py Outdated

jyalimand others added 2 commits February 25, 2026 22:25

Update Doc/library/datetime.rst
9b29dbb
typo fix Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Update Lib/test/datetimetester.py
d199d0b
remove trailing whitespace Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

jyalim changed the title ~~gh-140715: Add %t format code support to strptime()~~gh-140715: Add %t and %n format codes support to strptime()Feb 26, 2026

jyalim added 6 commits February 25, 2026 22:54

correctly capture '' with '\s*' instead of '\s+'
dac5692

update tests with subtests for all whitespace chars covered by '\s'
e9927fb

init %n support for strptime
c674612

init tests for %n support in strptime
3a26205

update docs for %n support; drop (0) in footnote
f709b80

update NEWS to include %n
924b7cf

%n before %t to match general style
ed87c7d

StanFromIreland reviewed Feb 26, 2026
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Comment threadLib/test/test_strptime.py Outdated

jyalim added 2 commits February 28, 2026 15:46

merge tests; fix formatting
9541826

directive
2f91a57

StanFromIreland reviewed Mar 1, 2026
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Comment threadDoc/library/datetime.rst Outdated
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Comment threadMisc/NEWS.d/next/Library/2026-02-17-03-43-07.gh-issue-140715.twmcM_.rst Outdated
Comment threadLib/test/test_strptime.py Outdated

jyalimand others added 4 commits March 1, 2026 07:49

Update Doc/library/datetime.rst
608c638
clarify "arbitrary" with "zero or more" Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Update Doc/library/datetime.rst
4a4d722
clarify "arbitrary" with "zero or more" Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Update Misc/NEWS.d/next/Library/2026-02-17-03-43-07.gh-issue-140715.t…
4080b03
…wmcM_.rst Drop quotes around format directives Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Merge branch 'main' into fix-issue-140715--t
bbe7d2e

replace vars with literals, as requested
ab9d41a

StanFromIreland reviewed Mar 2, 2026
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Comment threadLib/test/datetimetester.py

Apply suggestion from@StanFromIreland
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StanFromIreland approved these changes Mar 2, 2026
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bedevere-appBot added awaiting core review and removed awaiting review labels Mar 2, 2026

encukou reviewed Mar 3, 2026
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jyalimand others added 5 commits March 3, 2026 06:44

Update Lib/_strptime.py
4c31a92
PEP 8 fix on existing code Co-authored-by: Petr Viktorin <encukou@gmail.com>

Update Lib/test/datetimetester.py
3d7c3c7
PEP 8 comma for exploded function arguments Co-authored-by: Petr Viktorin <encukou@gmail.com>

refactor tests to include joint directive tests, %n%t and %t%n; a…
d6ca685
…lso add PEP 8 trailing commas to all exploded function arguments

bump test date by two days to distinguish from month (02) and default…
4e366cb
… day (01)

reorder helper tuples to reflect loop order
9f5a37e

encukou merged commit f884dc6 into python:mainMar 13, 2026
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bedevere-appBot removed the awaiting core review label Mar 13, 2026

jyalim mentioned this pull request Mar 15, 2026
gh-140715: Add %C format code support to strptime() #145955
Open

ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
pythongh-140715: Add %t and %n format codes support to strptime() (py…
95fcb94
…thonGH-144896) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

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