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.

Doc/library/datetime.rst

Lib/test/datetimetester.py

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!

Doc/library/datetime.rst

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)

Doc/library/datetime.rst

Lib/test/datetimetester.py

Lib/_strptime.py

Lib/test/datetimetester.py

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.

Lib/test/datetimetester.py

Lib/test/test_strptime.py

jyalim · 2026-02-28T22:56:10Z

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

Doc/library/datetime.rst

Misc/NEWS.d/next/Library/2026-02-17-03-43-07.gh-issue-140715.twmcM_.rst

Lib/test/test_strptime.py

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.

Lib/test/datetimetester.py

StanFromIreland

LGTM

Lib/_strptime.py

Lib/test/datetimetester.py

encukou · 2026-03-03T12:02:11Z

Lib/test/datetimetester.py


+    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.

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)

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-app bot added the awaiting review label Feb 17, 2026

bedevere-app bot mentioned this pull request Feb 17, 2026

Update str*time to C11 format codes #140715

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blurb-it bot and others added 2 commits February 17, 2026 03:43

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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

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update docs to reflect powerful %t strptime functionality

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simplify docs, as requested

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jyalim and others added 2 commits February 25, 2026 22:25

Update Doc/library/datetime.rst

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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

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jyalim added 2 commits February 28, 2026 15:46

merge tests; fix formatting

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directive

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jyalim and others added 4 commits March 1, 2026 07:49

Update Doc/library/datetime.rst

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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

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replace vars with literals, as requested

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jyalim and 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

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