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from sqlalchemy import types
from ..exceptions import ImproperlyConfigured
from .scalar_coercible import ScalarCoercible
class TimezoneType(ScalarCoercible, types.TypeDecorator):
"""
TimezoneType provides a way for saving timezones objects into database.
TimezoneType saves timezone objects as strings on the way in and converts
them back to objects when querying the database.
::
from sqlalchemy_utils import TimezoneType
class User(Base):
__tablename__ = 'user'
# Pass backend='pytz' to change it to use pytz. Other values:
# 'dateutil' (default), and 'zoneinfo'.
timezone = sa.Column(TimezoneType(backend='pytz'))
:param backend: Whether to use 'dateutil', 'pytz' or 'zoneinfo' for
timezones. 'zoneinfo' uses the standard library module in Python 3.9+,
but requires the external 'backports.zoneinfo' package for older
Python versions.
"""
impl = types.Unicode(50)
python_type = None
cache_ok = True
def __init__(self, backend='dateutil'):
self.backend = backend
if backend == 'dateutil':
try:
from dateutil.tz import tzfile
from dateutil.zoneinfo import get_zonefile_instance
self.python_type = tzfile
self._to = get_zonefile_instance().zones.get
self._from = lambda x: str(x._filename)
except ImportError:
raise ImproperlyConfigured(
"'python-dateutil' is required to use the "
"'dateutil' backend for 'TimezoneType'"
)
elif backend == 'pytz':
try:
from pytz import timezone
from pytz.tzinfo import BaseTzInfo
self.python_type = BaseTzInfo
self._to = timezone
self._from = str
except ImportError:
raise ImproperlyConfigured(
"'pytz' is required to use the 'pytz' backend "
"for 'TimezoneType'"
)
elif backend == "zoneinfo":
try:
import zoneinfo
except ImportError:
try:
from backports import zoneinfo
except ImportError:
raise ImproperlyConfigured(
"'backports.zoneinfo' is required to use "
"the 'zoneinfo' backend for 'TimezoneType'"
"on Python version < 3.9"
)
self.python_type = zoneinfo.ZoneInfo
self._to = zoneinfo.ZoneInfo
self._from = str
else:
raise ImproperlyConfigured(
"'pytz', 'dateutil' or 'zoneinfo' are the backends "
"supported for 'TimezoneType'"
)
def _coerce(self, value):
if value is not None and not isinstance(value, self.python_type):
obj = self._to(value)
if obj is None:
raise ValueError("unknown time zone '%s'" % value)
return obj
return value
def process_bind_param(self, value, dialect):
return self._from(self._coerce(value)) if value else None
def process_result_value(self, value, dialect):
return self._to(value) if value else None
|
