psycopg2/lib/tz.py

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"""tzinfo implementations for psycopg2
This module holds two different tzinfo implementations that can be used as
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the 'tzinfo' argument to datetime constructors, directly passed to psycopg
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functions or used to set the .tzinfo_factory attribute in cursors.
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"""
# psycopg/tz.py - tzinfo implementation
#
# Copyright (C) 2003-2019 Federico Di Gregorio <fog@debian.org>
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# Copyright (C) 2020 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)
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class FixedOffsetTimezone(datetime.tzinfo):
"""Fixed offset in minutes east from UTC.
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This is exactly the implementation__ found in Python 2.3.x documentation,
with a small change to the `!__init__()` method to allow for pickling
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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.
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.. __: https://docs.python.org/library/datetime.html
"""
_name = None
_offset = ZERO
_cache = {}
def __init__(self, offset=None, name=None):
if offset is not None:
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self._offset = datetime.timedelta(minutes=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(FixedOffsetTimezone, cls).__new__(cls, offset, name)
cls._cache[key] = tz
return tz
def __repr__(self):
offset_mins = self._offset.seconds // 60 + self._offset.days * 24 * 60
return "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=%r)" \
% (offset_mins, self._name)
def __getinitargs__(self):
offset_mins = self._offset.seconds // 60 + self._offset.days * 24 * 60
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return offset_mins, self._name
def utcoffset(self, dt):
return self._offset
def tzname(self, dt):
if self._name is not None:
return self._name
else:
seconds = self._offset.seconds + self._offset.days * 86400
hours, seconds = divmod(seconds, 3600)
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minutes = seconds / 60
if minutes:
return "%+03d:%d" % (hours, minutes)
else:
return "%+03d" % hours
def dst(self, dt):
return ZERO
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STDOFFSET = datetime.timedelta(seconds=-time.timezone)
if time.daylight:
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DSTOFFSET = datetime.timedelta(seconds=-time.altzone)
else:
DSTOFFSET = STDOFFSET
DSTDIFF = DSTOFFSET - STDOFFSET
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class LocalTimezone(datetime.tzinfo):
"""Platform idea of local timezone.
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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
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LOCAL = LocalTimezone()
# TODO: pre-generate some interesting time zones?