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"""tzinfo implementations for psycopg2
This module holds two different tzinfo implementations that can be used as
the 'tzinfo' argument to datetime constructors, directly passed to psycopg
functions or used to set the .tzinfo_factory attribute in cursors.
"""
# psycopg/tz.py - tzinfo implementation
#
# Copyright (C) 2003-2019 Federico Di Gregorio <fog@debian.org>
# Copyright (C) 2020-2021 The Psycopg Team
#
# psycopg2 is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# In addition, as a special exception, the copyright holders give
# permission to link this program with the OpenSSL library (or with
# modified versions of OpenSSL that use the same license as OpenSSL),
# and distribute linked combinations including the two.
#
# You must obey the GNU Lesser General Public License in all respects for
# all of the code used other than OpenSSL.
#
# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
# License for more details.
import datetime
import time
ZERO = datetime.timedelta(0)
class FixedOffsetTimezone(datetime.tzinfo):
"""Fixed offset in minutes east from UTC.
This is exactly the implementation__ found in Python 2.3.x documentation,
with a small change to the `!__init__()` method to allow for pickling
and a default name in the form ``sHH:MM`` (``s`` is the sign.).
The implementation also caches instances. During creation, if a
FixedOffsetTimezone instance has previously been created with the same
offset and name that instance will be returned. This saves memory and
improves comparability.
.. versionchanged:: 2.9
The constructor can take either a timedelta or a number of minutes of
offset. Previously only minutes were supported.
.. __: https://docs.python.org/library/datetime.html
"""
_name = None
_offset = ZERO
_cache = {}
def __init__(self, offset=None, name=None):
if offset is not None:
if not isinstance(offset, datetime.timedelta):
offset = datetime.timedelta(minutes=offset)
self._offset = offset
if name is not None:
self._name = name
def __new__(cls, offset=None, name=None):
"""Return a suitable instance created earlier if it exists
"""
key = (offset, name)
try:
return cls._cache[key]
except KeyError:
tz = super().__new__(cls, offset, name)
cls._cache[key] = tz
return tz
def __repr__(self):
return "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=%r)" \
% (self._offset, self._name)
def __eq__(self, other):
if isinstance(other, FixedOffsetTimezone):
return self._offset == other._offset
else:
return NotImplemented
def __ne__(self, other):
if isinstance(other, FixedOffsetTimezone):
return self._offset != other._offset
else:
return NotImplemented
def __getinitargs__(self):
return self._offset, self._name
def utcoffset(self, dt):
return self._offset
def tzname(self, dt):
if self._name is not None:
return self._name
minutes, seconds = divmod(self._offset.total_seconds(), 60)
hours, minutes = divmod(minutes, 60)
rv = "%+03d" % hours
if minutes or seconds:
rv += ":%02d" % minutes
if seconds:
rv += ":%02d" % seconds
return rv
def dst(self, dt):
return ZERO
STDOFFSET = datetime.timedelta(seconds=-time.timezone)
if time.daylight:
DSTOFFSET = datetime.timedelta(seconds=-time.altzone)
else:
DSTOFFSET = STDOFFSET
DSTDIFF = DSTOFFSET - STDOFFSET
class LocalTimezone(datetime.tzinfo):
"""Platform idea of local timezone.
This is the exact implementation from the Python 2.3 documentation.
"""
def utcoffset(self, dt):
if self._isdst(dt):
return DSTOFFSET
else:
return STDOFFSET
def dst(self, dt):
if self._isdst(dt):
return DSTDIFF
else:
return ZERO
def tzname(self, dt):
return time.tzname[self._isdst(dt)]
def _isdst(self, dt):
tt = (dt.year, dt.month, dt.day,
dt.hour, dt.minute, dt.second,
dt.weekday(), 0, -1)
stamp = time.mktime(tt)
tt = time.localtime(stamp)
return tt.tm_isdst > 0
LOCAL = LocalTimezone()
# TODO: pre-generate some interesting time zones?