GH-15047: [Python]: switch from pytz to zoneinfo by default for string to tzinfo conversion - #49694
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jorisvandenbossche merged 7 commits intoMay 22, 2026
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… string to tzinfo conversion
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Revision: c2c973a Submitted crossbow builds: ursacomputing/crossbow @ actions-02d567dab2
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jorisvandenbossche
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April 9, 2026 12:24
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As far as I can see, all failures in the above crossbow builds (after the last update) are unrelated (docker/git/download failures) |
AlenkaF
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LGTM, thanks! Added only one minor comment.
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After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit 9583eb7. There weren't enough matching historic benchmark results to make a call on whether there were regressions. The full Conbench report has more details. |
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… string to tzinfo conversion (apache#49694) ### Rationale for this change `zoneinfo` is available starting with Python 3.9, so we can now assume that it is available, and so we can switch from returning `pytz` timezones by default to return `zoneinfo` timezones (or `datetime.timezone` for fixed offsets). Only keeping pytz as fallback for strings that are not supported by `zoneinfo` but were supported by `pytz`. Later, we should maybe deprecate that fallback. Generally we should move away from using `pytz`, since the core functionality of having time zones is now available in the standard library (`zoneinfo`), and because the pytz package has several warts / incompatibilities with stdlib datetime (https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html) ### What changes are included in this PR? Whenever we create a python timezone object, which is when converting to pandas or when converting to a `datetime.datetime` object: - always prefer `zoneinfo` for `datetime.datetime` objects - prefer `zoneinfo` for pandas objects _if_ pandas >= 3, to align with the change on the pandas side (pandas-dev/pandas#34916) In either case, when preferring `zoneinfo`, we still fall back to `pytz` for named timezones if `zoneinfo` does not recognize the zone name (apparently pytz can have some common (older) aliases that might not always work with zoneinfo). This fallback is something we could deprecate and remove later on (so we can eventually remove all usage of pytz) ### Are these changes tested? Yes ### Are there any user-facing changes? **This PR includes breaking changes to public APIs.** It is a different object that we return (different class, i.e. `zoneinfo.ZoneInfo` instead of a `pytz.tzinfo.BaseTzInfo`, both are still subclasses of `datetime.tzinfo`), which has some differences in the API, so for people relying on that, this is a breaking change. For the conversion to pandas, pandas itself has made this breaking change anyhow, so for those cases it aligns with that change of pandas. * GitHub Issue: apache#15047
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…robust for platforms supporting lower case tz names (#50042) ### Rationale for this change Fix failing test on CI as reported in #50041, for a test added in #49694 ### What changes are included in this PR? The test relies on the lower case "europe/brussels" time zone name not being recognized by `zoneinfo` (and it generally is by `pytz`). But apparently on some platforms, `zoneinfo` does accept this. Updating the test to first test this, and thus skip the test dynamically. * GitHub Issue: #50041 Authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com> Signed-off-by: Raúl Cumplido <raulcumplido@gmail.com>
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Rationale for this change
zoneinfois available starting with Python 3.9, so we can now assume that it is available, and so we can switch from returningpytztimezones by default to returnzoneinfotimezones (ordatetime.timezonefor fixed offsets).Only keeping pytz as fallback for strings that are not supported by
zoneinfobut were supported bypytz. Later, we should maybe deprecate that fallback.Generally we should move away from using
pytz, since the core functionality of having time zones is now available in the standard library (zoneinfo), and because the pytz package has several warts / incompatibilities with stdlib datetime (https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html)What changes are included in this PR?
Whenever we create a python timezone object, which is when converting to pandas or when converting to a
datetime.datetimeobject:zoneinfofordatetime.datetimeobjectszoneinfofor pandas objects if pandas >= 3, to align with the change on the pandas side (API: Default to stdlib timezone objects instead of pytz pandas-dev/pandas#34916)In either case, when preferring
zoneinfo, we still fall back topytzfor named timezones ifzoneinfodoes not recognize the zone name (apparently pytz can have some common (older) aliases that might not always work with zoneinfo).This fallback is something we could deprecate and remove later on (so we can eventually remove all usage of pytz)
Are these changes tested?
Yes
Are there any user-facing changes?
This PR includes breaking changes to public APIs.
It is a different object that we return (different class, i.e.
zoneinfo.ZoneInfoinstead of apytz.tzinfo.BaseTzInfo, both are still subclasses ofdatetime.tzinfo), which has some differences in the API, so for people relying on that, this is a breaking change.For the conversion to pandas, pandas itself has made this breaking change anyhow, so for those cases it aligns with that change of pandas.