def localtime(dt=None, isdst=-1):
"""Return local time as an aware datetime object.
If called without arguments, return current time. Otherwise *dt*
argument should be a datetime instance, and it is converted to the
local time zone according to the system time zone database. If *dt* is
naive (that is, dt.tzinfo is None), it is assumed to be in local time.
In this case, a positive or zero value for *isdst* causes localtime to
presume initially that summer time (for example, Daylight Saving Time)
is or is not (respectively) in effect for the specified time. A
negative value for *isdst* causes the localtime() function to attempt
to divine whether summer time is in effect for the specified time.
"""
if dt is None:
return datetime.datetime.now(datetime.timezone.utc).astimezone()
if dt.tzinfo is not None:
return dt.astimezone()
# We have a naive datetime. Convert to a (localtime) timetuple and pass to
# system mktime together with the isdst hint. System mktime will return
# seconds since epoch.
tm = dt.timetuple()[:-1] + (isdst,)
seconds = time.mktime(tm)
localtm = time.localtime(seconds)
try:
delta = datetime.timedelta(seconds=localtm.tm_gmtoff)
tz = datetime.timezone(delta, localtm.tm_zone)
except AttributeError:
# Compute UTC offset and compare with the value implied by tm_isdst.
# If the values match, use the zone name implied by tm_isdst.
delta = dt - datetime.datetime(*time.gmtime(seconds)[:6])
dst = time.daylight and localtm.tm_isdst > 0
gmtoff = -(time.altzone if dst else time.timezone)
if delta == datetime.timedelta(seconds=gmtoff):
tz = datetime.timezone(delta, time.tzname[dst])
else:
tz = datetime.timezone(delta)
return dt.replace(tzinfo=tz)
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