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In order to represent aware datetime
objects (see the datetime documentation
for a discussion of aware vs. naive times), we'll need a
class derived from datetime.tzinfo to
represent the timestamps from the log files.
We don't have to worry about Daylight Saving Time, because the time zone in the log record is encoded as “-0700” or “-0600” depending on the time of year. So for our uses, a time zone object with a fixed offset will be fine.
The code below was cribbed pretty much directly from the
example class FixedOffset in the datetime documentation, so we'll present it here
with minimal comments.
# - - - - - c l a s s F i x e d T i m e Z o n e
class FixedTimeZone(datetime.tzinfo):
'''Represents a time zone that's always the same offset from UTC.
Exports:
FixedTimeZone ( mmEast, name ):
[ (mmEast is a zone offset represented by the number of
minutes east of UTC, or negative for west) and
(name is a time zone name as a string) ->
return a new FixedTimeZone instance with those
values ]
.utcoffset(dt):
[ dt is a datetime.datetime instance ->
return self's offset as a datetime.timedelta
instance ]
.tzname(dt):
[ return self's name ]
.dst(dt):
[ return a datetime.timedelta of zero ]
State/Invariants:
.__offset: [ self's offset as a datetime.timedelta ]
.__name: [ self's name, as passed to constructor ]
.ZERO: [ a zero datetime.timedelta ]
'''
ZERO = datetime.timedelta ( 0 )
def __init__ ( self, mmEast, name ):
'''Constructor
'''
self.__offset = datetime.timedelta ( minutes=mmEast )
self.__name = name
def utcoffset ( self, dt ):
return self.__offset
def tzname ( self, dt ):
return self.__name
def dst ( self, dt ):
return self.ZERO