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https://github.com/psycopg/psycopg2.git
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bca7200b3f
Avoid creating new a new FixedOffsetTimezone instance if one with the same offset and name has been created before. This will save memory when returning many rows containing "timestamp with timezone" columns, and also improves comparability.
134 lines
4.2 KiB
Python
134 lines
4.2 KiB
Python
"""tzinfo implementations for psycopg2
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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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"""
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# psycopg/tz.py - tzinfo implementation
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#
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# Copyright (C) 2003-2010 Federico Di Gregorio <fog@debian.org>
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#
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# psycopg2 is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# In addition, as a special exception, the copyright holders give
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# permission to link this program with the OpenSSL library (or with
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# modified versions of OpenSSL that use the same license as OpenSSL),
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# and distribute linked combinations including the two.
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#
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# You must obey the GNU Lesser General Public License in all respects for
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# all of the code used other than OpenSSL.
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#
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# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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# License for more details.
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import datetime
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import time
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ZERO = datetime.timedelta(0)
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class FixedOffsetTimezone(datetime.tzinfo):
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"""Fixed offset in minutes east from UTC.
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This is exactly the implementation__ found in Python 2.3.x documentation,
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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.).
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The implementation also caches instances. During creation, if a
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FixedOffsetTimezone instance has previously been created with the same
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offset and name that instance will be returned. This saves memory and
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improves comparability.
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.. __: http://docs.python.org/library/datetime.html#datetime-tzinfo
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"""
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_name = None
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_offset = ZERO
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_cache = {}
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def __init__(self, offset=None, name=None):
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if offset is not None:
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self._offset = datetime.timedelta(minutes = offset)
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if name is not None:
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self._name = name
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def __new__(cls, offset=None, name=None):
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"""Return a suitable instance created earlier if it exists
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"""
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key = (offset, name)
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try:
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return cls._cache[key]
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except KeyError:
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tz = datetime.tzinfo.__new__(cls, offset, name)
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tz.__init__(offset, name)
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cls._cache[key] = tz
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return tz
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def __repr__(self):
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offset_mins = self._offset.seconds // 60 + self._offset.days * 24 * 60
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return "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=%r)" \
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% (offset_mins, self._name)
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def utcoffset(self, dt):
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return self._offset
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def tzname(self, dt):
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if self._name is not None:
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return self._name
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else:
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seconds = self._offset.seconds + self._offset.days * 86400
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hours, seconds = divmod(seconds, 3600)
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minutes = seconds/60
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if minutes:
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return "%+03d:%d" % (hours, minutes)
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else:
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return "%+03d" % hours
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def dst(self, dt):
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return ZERO
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STDOFFSET = datetime.timedelta(seconds = -time.timezone)
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if time.daylight:
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DSTOFFSET = datetime.timedelta(seconds = -time.altzone)
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else:
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DSTOFFSET = STDOFFSET
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DSTDIFF = DSTOFFSET - STDOFFSET
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class LocalTimezone(datetime.tzinfo):
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"""Platform idea of local timezone.
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This is the exact implementation from the Python 2.3 documentation.
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"""
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def utcoffset(self, dt):
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if self._isdst(dt):
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return DSTOFFSET
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else:
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return STDOFFSET
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def dst(self, dt):
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if self._isdst(dt):
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return DSTDIFF
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else:
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return ZERO
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def tzname(self, dt):
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return time.tzname[self._isdst(dt)]
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def _isdst(self, dt):
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tt = (dt.year, dt.month, dt.day,
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dt.hour, dt.minute, dt.second,
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dt.weekday(), 0, -1)
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stamp = time.mktime(tt)
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tt = time.localtime(stamp)
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return tt.tm_isdst > 0
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LOCAL = LocalTimezone()
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# TODO: pre-generate some interesting time zones?
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