def _get_tail(self):
"Read the part of the data after last_timeseries_end_date"
self.tail = []
date = self.last_timeseries_end_date
saveddir = os.getcwd()
try:
os.chdir(self.filename)
# We assume that the first possible file we need to read is the
# previous than what it seems initially, because of the possibility
# of a DST offset interfering (I think that actually a negative DST
# offset would be needed for this to be a problem - but let's be
# safe and not sorry) (note that if the date is 0001-01-01 it
# means that the time series in the database is empty and we'll
# upload it in its entirety anyway, so no need to do the trick
# [which would fail because dates can't be less than that]).
a = add_months_to_datetime(date, -1) if date.year > 1 else date
first_file = '{0.year:04}-{0.month:02}.wlk'.format(a)
filename_regexp = re.compile(r'\d{4}-\d{2}.wlk$')
data_files = [x for x in glob('*.wlk')
if filename_regexp.match(x) and x >= first_file]
data_files.sort()
for current_file in data_files:
self.tail.extend(self._get_tail_part(date, current_file))
finally:
os.chdir(saveddir)