fd4abe522e
* Create rule S6890: zoneinfo should be preferred to pytz when using Python 3.9 and later * Fix after review * Fix after review --------- Co-authored-by: guillaume-dequenne-sonarsource <guillaume-dequenne-sonarsource@users.noreply.github.com> Co-authored-by: David Kunzmann <david.kunzmann@sonarsource.com> Co-authored-by: Guillaume Dequenne <guillaume.dequenne@sonarsource.com>
52 lines
2.3 KiB
Plaintext
52 lines
2.3 KiB
Plaintext
This rule raises an issue when using the `pytz` library on a codebase using Python 3.9 or later.
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== Why is this an issue?
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In Python 3.9 and later, the `zoneinfo` module is the recommended tool for handling timezones, replacing the `pytz` library. This recommendation is based on several key advantages.
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First, `zoneinfo` is part of Python's standard library, making it readily available without needing additional installation, unlike `pytz`.
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Second, `zoneinfo` integrates seamlessly with Python's datetime module. You can directly use `zoneinfo` timezone objects when creating `datetime` objects, making it more intuitive and less error-prone than `pytz`, which requires a separate localize method for this purpose.
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Third, `zoneinfo` handles historical timezone changes more accurately than `pytz`. When a `pytz` timezone object is used, it defaults to the earliest known offset, which can lead to unexpected results. `zoneinfo` does not have this issue.
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Lastly, `zoneinfo` uses the system's IANA time zone database when available, ensuring it works with the most up-to-date timezone data. In contrast, `pytz` includes its own copy of the IANA database, which may not be as current.
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In summary, `zoneinfo` offers a more modern, intuitive, and reliable approach to handling timezones in Python 3.9 and later, making it the preferred choice over `pytz`.
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== How to fix it
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To fix this is issue use a `zoneinfo` timezone object when constructing a `datetime` instead of the `pytz` library.
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=== Code examples
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==== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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from datetime import datetime
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import pytz
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dt = pytz.timezone('America/New_York'').localize(datetime(2022, 1, 1)) # Noncompliant: the localize method is needed to avoid bugs (see S6887)
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----
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==== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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from datetime import datetime
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from zoneinfo import ZoneInfo
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dt = datetime(2022, 1, 1, tzinfo=ZoneInfo('America/New_York')) # OK: timezone object can be used safely through the datetime constructor
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----
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== Resources
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=== Documentation
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* PEP 615 - https://peps.python.org/pep-0615/[Support for the IANA Time Zone Database in the Standard Library]
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=== Related rules
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* S6887 - pytz.timezone should not be passed to the datetime.datetime constructor
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