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91 lines
2.9 KiB
91 lines
2.9 KiB
3 years ago
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"""
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This module contains helper functions to ease the transition from ``pytz`` to
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another :pep:`495`-compatible library.
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"""
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from . import _common, _compat
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from ._impl import _PytzShimTimezone
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_PYTZ_BASE_CLASSES = None
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def is_pytz_zone(tz):
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"""Check if a time zone is a ``pytz`` time zone.
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This will only import ``pytz`` if it has already been imported, and does
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not rely on the existence of the ``localize`` or ``normalize`` methods
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(since the shim classes also have these methods, but are not ``pytz``
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zones).
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"""
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# If pytz is not in sys.modules, then we will assume the time zone is not a
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# pytz zone. It is possible that someone has manipulated sys.modules to
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# remove pytz, but that's the kind of thing that causes all kinds of other
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# problems anyway, so we'll call that an unsupported configuration.
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if not _common.pytz_imported():
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return False
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if _PYTZ_BASE_CLASSES is None:
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_populate_pytz_base_classes()
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return isinstance(tz, _PYTZ_BASE_CLASSES)
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def upgrade_tzinfo(tz):
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"""Convert a ``pytz`` or shim timezone into its modern equivalent.
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The shim classes are thin wrappers around :mod:`zoneinfo` or
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:mod:`dateutil.tz` implementations of the :class:`datetime.tzinfo` base
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class. This function removes the shim and returns the underlying "upgraded"
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time zone.
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When passed a ``pytz`` zone (not a shim), this returns the non-``pytz``
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equivalent. This may fail if ``pytz`` is using a data source incompatible
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with the upgraded provider's data source, or if the ``pytz`` zone was built
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from a file rather than an IANA key.
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When passed an object that is not a shim or a ``pytz`` zone, this returns
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the original object.
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:param tz:
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A :class:`datetime.tzinfo` object.
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:raises KeyError:
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If a ``pytz`` zone is passed to the function with no equivalent in the
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:pep:`495`-compatible library's version of the Olson database.
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:return:
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A :pep:`495`-compatible equivalent of any ``pytz`` or shim
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class, or the original object.
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"""
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if isinstance(tz, _PytzShimTimezone):
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return tz._zone
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if is_pytz_zone(tz):
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if tz.zone is None:
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# This is a fixed offset zone
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offset = tz.utcoffset(None)
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offset_minutes = offset.total_seconds() / 60
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return _compat.get_fixed_offset_zone(offset_minutes)
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if tz.zone == "UTC":
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return _compat.UTC
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return _compat.get_timezone(tz.zone)
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return tz
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def _populate_pytz_base_classes():
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import pytz
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from pytz.tzinfo import BaseTzInfo
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base_classes = (BaseTzInfo, pytz._FixedOffset)
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# In releases prior to 2018.4, pytz.UTC was not a subclass of BaseTzInfo
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if not isinstance(pytz.UTC, BaseTzInfo): # pragma: nocover
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base_classes = base_classes + (type(pytz.UTC),)
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global _PYTZ_BASE_CLASSES
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_PYTZ_BASE_CLASSES = base_classes
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