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gh-70647: Better promote how to safely parse yearless dates in datetime. - #116179
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…datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works.
itamaro
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Mar 1, 2024
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encukou
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Apr 2, 2024
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Perhaps this should be only merged to the backport branches, not main. |
pganssle
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Apr 2, 2024
willingc
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Oct 30, 2024
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@gpshead Looks like this may need some tidying up if you are still interested. |
willingc
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October 30, 2024 18:06
StanFromIreland
commented
Mar 15, 2025
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This has already been partially implemented (the smaller note) do we still want to add the larger note since its deprecated anyway? |
gpshead
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Mar 21, 2025
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Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14. |
miss-islington pushed a commit
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Dec 21, 2025
…datetime. (pythonGH-116179) * pythongh-70647: Better promote how to safely parse yearless dates in datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works. * doctest code within note is bad, dedent. * Update to match the error message. * remove no longer referenced footnote * ignore the warning in the doctest * use Petr's suggestion for the docs to hide the warning processing * cover date.strptime (3.14) as well (cherry picked from commit b8d3fdd) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
GH-143037 is a backport of this pull request to the 3.14 branch. |
gpshead
commented
Dec 21, 2025
MemberAuthor
I realize we may simplify the text around this when we actually do the deprecation behavior change (which we could choose to do now that we're 3.15 though it's nicer to wait longer). But having the detail in the docs and the backport to the stable docs still seems good so I fixed this up. a backport to 3.13 docs will need to be manual due to the added method in 3.14. |
gpshead added a commit
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Dec 21, 2025
… datetime. (GH-116179) (#143037) gh-70647: Better promote how to safely parse yearless dates in datetime. (GH-116179) * gh-70647: Better promote how to safely parse yearless dates in datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works. * doctest code within note is bad, dedent. * Update to match the error message. * remove no longer referenced footnote * ignore the warning in the doctest * use Petr's suggestion for the docs to hide the warning processing * cover date.strptime (3.14) as well (cherry picked from commit b8d3fdd) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
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Dec 21, 2025
…datetime. (pythonGH-116179) * pythongh-70647: Better promote how to safely parse yearless dates in datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works. * doctest code within note is bad, dedent. * Update to match the error message. * remove no longer referenced footnote * ignore the warning in the doctest * use Petr's suggestion for the docs to hide the warning processing * cover date.strptime (3.14) as well
GH-143038 is a backport of this pull request to the 3.13 branch. |
gpshead added a commit
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Dec 21, 2025
… datetime. (GH-116179) (#143038) * gh-70647: Better promote how to safely parse yearless dates in datetime. (GH-116179) * gh-70647: Better promote how to safely parse yearless dates in datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works. * doctest code within note is bad, dedent. * Update to match the error message. * remove no longer referenced footnote * ignore the warning in the doctest * use Petr's suggestion for the docs to hide the warning processing * cover date.strptime (3.14) as well * remove date.strptime mentions from 3.14
cocolato pushed a commit
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Dec 22, 2025
…datetime. (pythonGH-116179) * pythongh-70647: Better promote how to safely parse yearless dates in datetime. Every four years people encounter this because it just isn't obvious. This moves the footnote up to a note with a code example. We'd love to change the default year value for datetime but doing that could have other consequences for existing code. This documented workaround *always* works. * doctest code within note is bad, dedent. * Update to match the error message. * remove no longer referenced footnote * ignore the warning in the doctest * use Petr's suggestion for the docs to hide the warning processing * cover date.strptime (3.14) as well
lucc added a commit
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Feb 18, 2026
Python uses 1900 as the default year if a partial date is parsed with datetime.datetime.strptime. This fails for February 29th because 1900 is not a leap year. This is discussed in #335 and upstream in python/cpython#116179.
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Every four years people encounter this in part because it just isn't obvious that partial incomplete date parsing is not what
datetime.strptimeis designed for. This moves the footnote up to a more explanatory inline note with a code example.We'd love the default year value for datetime to be different, but changing that could have other consequences for existing code. This documented workaround always works.
📚 Documentation preview 📚: https://cpython-previews--116179.org.readthedocs.build/