Convert a date with UTC timezone offset to corresponding local timezone format

since your input already contains a UTC offset, you can parse the iso-format string to aware datetime (tzinfo set) and use astimezone to set the correct time zone. Using pytz:

from datetime import datetime
from pytz import timezone # Python 3.9: zoneinfo (standard lib)

str_date = '2020-01-01T00:00:00-08:00'

# to datetime
dt = datetime.fromisoformat(str_date)

# to tz
dt_tz = dt.astimezone(timezone("America/Los_Angeles"))

print(dt_tz)
# 2020-01-01 00:00:00-08:00
print(repr(dt_tz))
# datetime.datetime(2020, 1, 1, 0, 0, tzinfo=<DstTzInfo 'America/Los_Angeles' PST-1 day, 16:00:00 STD>)
print(dt_tz.strftime("%a, %d %b %Y %H:%M:%S %Z"))
# Wed, 01 Jan 2020 00:00:00 PST

See also: Display the time in a different time zone - e.g. this answer for a Python 3.9/zoneinfo example.