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132 lines
5.2 KiB
132 lines
5.2 KiB
Metadata-Version: 2.1
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Name: pytz_deprecation_shim
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Version: 0.1.0.post0
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Summary: Shims to make deprecation of pytz easier
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Home-page: https://github.com/pganssle/pytz-deprecation-shim
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Author: Paul Ganssle
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Author-email: paul@ganssle.io
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License: Apache-2.0
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Project-URL: Source, https://github.com/pganssle/pytz-deprecation-shim
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Project-URL: Bug Reports, https://github.com/pganssle/pytz-deprecation-shim/issues
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Project-URL: Documentation, https://pytz-deprecation-shim.readthedocs.io
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Classifier: Development Status :: 4 - Beta
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Classifier: Intended Audience :: Developers
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Classifier: License :: OSI Approved :: Apache Software License
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Classifier: Programming Language :: Python :: 2
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Classifier: Programming Language :: Python :: 2.7
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Classifier: Programming Language :: Python :: 3
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Classifier: Programming Language :: Python :: 3.6
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Classifier: Programming Language :: Python :: 3.7
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Classifier: Programming Language :: Python :: 3.8
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Classifier: Programming Language :: Python :: 3.9
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Requires-Python: !=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*,>=2.7
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Description-Content-Type: text/x-rst
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License-File: LICENSE
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License-File: licenses/LICENSE_APACHE
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Requires-Dist: python-dateutil ; python_version < "3.6"
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Requires-Dist: tzdata ; python_version >= "3.6"
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Requires-Dist: backports.zoneinfo ; python_version >= "3.6" and python_version < "3.9"
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pytz_deprecation_shim: Shims to help you safely remove pytz
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===========================================================
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``pytz`` has served the Python community well for many years, but it is no
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longer the best option for providing time zones. ``pytz`` has a non-standard
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interface that is `very easy to misuse
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<https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html>`_; this
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interface was necessary when ``pytz`` was created, because ``datetime`` had no
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way to represent ambiguous datetimes, but this was solved in in Python 3.6,
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which added a ``fold`` attribute to datetimes in `PEP 495
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<https://www.python.org/dev/peps/pep-0495/>`_. With the addition of the
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``zoneinfo`` module in Python 3.9 (`PEP 615
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<https://www.python.org/dev/peps/pep-0615/>`_), there has never been a better
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time to migrate away from ``pytz``.
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However, since ``pytz`` time zones are used very differently from a standard
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``tzinfo``, and many libraries have built ``pytz`` zones into their standard
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time zone interface (and thus may have users relying on the existence of the
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``localize`` and ``normalize`` methods); this library provides shim classes
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that are compatible with both PEP 495 and ``pytz``'s interface, to make it
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easier for libraries to deprecate ``pytz``.
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Usage
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=====
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This library is intended for *temporary usage only*, and should allow you to
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drop your dependency on ``pytz`` while also giving your users notice that
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eventually you will remove support for the ``pytz``-specific interface.
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Within your own code, use ``pytz_deprecation_shim.timezone`` shims as if they
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were ``zoneinfo`` or ``dateutil.tz`` zones — do not use ``localize`` or
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``normalize``:
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.. code-block:: pycon
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>>> import pytz_deprecation_shim as pds
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>>> from datetime import datetime, timedelta
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>>> LA = pds.timezone("America/Los_Angeles")
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>>> dt = datetime(2020, 10, 31, 12, tzinfo=LA)
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>>> print(dt)
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2020-10-31 12:00:00-07:00
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>>> dt.tzname()
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'PDT'
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Datetime addition will work `like normal Python datetime arithmetic
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<https://blog.ganssle.io/articles/2018/02/aware-datetime-arithmetic.html>`_,
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even across a daylight saving time transition:
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.. code-block:: pycon
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>>> dt_add = dt + timedelta(days=1)
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>>> print(dt_add)
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2020-11-01 12:00:00-08:00
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>>> dt_add.tzname()
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'PST'
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However, if you have exposed a time zone to end users who are using ``localize``
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and/or ``normalize`` or any other ``pytz``-specific features (or if you've
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failed to convert some of your own code all the way), those users will see
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a warning (rather than an exception) when they use those features:
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.. code-block:: pycon
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>>> dt = LA.localize(datetime(2020, 10, 31, 12))
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<stdin>:1: PytzUsageWarning: The localize method is no longer necessary, as
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this time zone supports the fold attribute (PEP 495). For more details on
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migrating to a PEP 495-compliant implementation, see
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https://pytz-deprecation-shim.readthedocs.io/en/latest/migration.html
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>>> print(dt)
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2020-10-31 12:00:00-07:00
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>>> dt.tzname()
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'PDT'
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>>> dt_add = LA.normalize(dt + timedelta(days=1))
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<stdin>:1: PytzUsageWarning: The normalize method is no longer necessary,
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as this time zone supports the fold attribute (PEP 495). For more details
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on migrating to a PEP 495-compliant implementation, see
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https://pytz-deprecation-shim.readthedocs.io/en/latest/migration.html
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>>> print(dt_add)
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2020-11-01 12:00:00-08:00
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>>> dt_add.tzname()
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'PST'
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For IANA time zones, calling ``str()`` on the shim zones (and indeed on ``pytz``
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and ``zoneinfo`` zones as well) returns the IANA key, so end users who would
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like to actively migrate to a ``zoneinfo`` (or ``backports.zoneinfo``) can do
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so:
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.. code-block:: pycon
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>>> from zoneinfo import ZoneInfo
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>>> LA = pds.timezone("America/Los_Angeles")
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>>> LA_zi = ZoneInfo(str(LA))
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>>> print(LA_zi)
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zoneinfo.ZoneInfo(key='America/Los_Angeles')
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