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bazarr/libs/pytz_deprecation_shim/helpers.py

91 lines
2.9 KiB

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