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# -*- test-case-name: twisted.python.test.test_tzhelper -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Time zone utilities.
"""
from datetime import datetime, timedelta, tzinfo
__all__ = [
"FixedOffsetTimeZone",
"UTC",
]
class FixedOffsetTimeZone(tzinfo):
"""
Represents a fixed timezone offset (without daylight saving time).
@ivar name: A L{str} giving the name of this timezone; the name just
includes how much time this offset represents.
@ivar offset: A L{timedelta} giving the amount of time this timezone is
offset.
"""
def __init__(self, offset, name=None):
"""
Construct a L{FixedOffsetTimeZone} with a fixed offset.
@param offset: a delta representing the offset from UTC.
@type offset: L{timedelta}
@param name: A name to be given for this timezone.
@type name: L{str} or L{NoneType}
"""
self.offset = offset
self.name = name
@classmethod
def fromSignHoursMinutes(cls, sign, hours, minutes):
"""
Construct a L{FixedOffsetTimeZone} from an offset described by sign
('+' or '-'), hours, and minutes.
@note: For protocol compatibility with AMP, this method never uses 'Z'
@param sign: A string describing the positive or negative-ness of the
offset.
@param hours: The number of hours in the offset.
@type hours: L{int}
@param minutes: The number of minutes in the offset
@type minutes: L{int}
@return: A time zone with the given offset, and a name describing the
offset.
@rtype: L{FixedOffsetTimeZone}
"""
name = "%s%02i:%02i" % (sign, hours, minutes)
if sign == "-":
hours = -hours
minutes = -minutes
elif sign != "+":
raise ValueError("Invalid sign for timezone %r" % (sign,))
return cls(timedelta(hours=hours, minutes=minutes), name)
@classmethod
def fromLocalTimeStamp(cls, timeStamp):
"""
Create a time zone with a fixed offset corresponding to a time stamp in
the system's locally configured time zone.
@param timeStamp: a time stamp
@type timeStamp: L{int}
@return: a time zone
@rtype: L{FixedOffsetTimeZone}
"""
offset = (
datetime.fromtimestamp(timeStamp) -
datetime.utcfromtimestamp(timeStamp)
)
return cls(offset)
def utcoffset(self, dt):
"""
Return this timezone's offset from UTC.
"""
return self.offset
def dst(self, dt):
"""
Return a zero C{datetime.timedelta} for the daylight saving time
offset, since there is never one.
"""
return timedelta(0)
def tzname(self, dt):
"""
Return a string describing this timezone.
"""
if self.name is not None:
return self.name
# XXX this is wrong; the tests are
dt = datetime.fromtimestamp(0, self)
return dt.strftime("UTC%z")
UTC = FixedOffsetTimeZone.fromSignHoursMinutes("+", 0, 0)
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