Created
September 20, 2020 02:13
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Simple script to convert between time zones.
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#! /usr/bin/env python3 | |
"""Simple timezone converter""" | |
import argparse | |
import datetime | |
import re | |
import sys | |
TZS = [ | |
# UTC | |
UTC := datetime.timezone.utc, | |
# Japan | |
JST := datetime.timezone(datetime.timedelta(hours=9), name='JST'), | |
# USA | |
PST := datetime.timezone(datetime.timedelta(hours=-8), name='PST'), | |
PDT := datetime.timezone(datetime.timedelta(hours=-7), name='PDT'), | |
MST := datetime.timezone(datetime.timedelta(hours=-7), name='MST'), | |
MDT := datetime.timezone(datetime.timedelta(hours=-6), name='MDT'), | |
CST := datetime.timezone(datetime.timedelta(hours=-6), name='CST'), | |
CDT := datetime.timezone(datetime.timedelta(hours=-5), name='CDT'), | |
EST := datetime.timezone(datetime.timedelta(hours=-5), name='EST'), | |
EDT := datetime.timezone(datetime.timedelta(hours=-4), name='EDT'), | |
# Australia | |
AWST := datetime.timezone(datetime.timedelta(hours=8), name='AWST'), | |
AWDT := datetime.timezone(datetime.timedelta(hours=9), name='AWDT'), | |
ACST := datetime.timezone(datetime.timedelta(hours=9, minutes=30), name='ACST'), | |
ACDT := datetime.timezone(datetime.timedelta(hours=10, minutes=30), name='ACDT'), | |
AEST := datetime.timezone(datetime.timedelta(hours=10), name='AEST'), | |
AEDT := datetime.timezone(datetime.timedelta(hours=11), name='AEDT'), | |
] | |
TIMEZONES = {tz.tzname(datetime.datetime.now()): tz for tz in TZS} | |
TIME_FORMAT = '%Y-%m-%d %H:%M:%S %Z (UTC%z)' | |
class ParseError(ValueError): | |
"""Errors in parsing inputs into valid values""" | |
def __init__(self, item, message): | |
self.item = item | |
self.message = message | |
def _parse_args(): | |
def upper(st): | |
return st.upper() | |
parser = argparse.ArgumentParser(prefix_chars=r'/-@', | |
formatter_class=argparse.RawDescriptionHelpFormatter, | |
description='Convert times between timezones', | |
epilog="""The following characters can be used as separators: | |
for date: ./-<space> | |
for time: .:<space> | |
If <space> is used, the date or time must be quoted. | |
In addition to ±HHMM, certain timezone names my be used for timezone.""") | |
parser.add_argument('date', help='date (YYYYMMDD)') | |
parser.add_argument('time', help='time (HHMMSS)') | |
parser.add_argument('timezone', help='timezone (±HHMM / name)', type=upper) | |
parser.add_argument('-t', '--target-timezone', metavar='±HHMM', dest='tgt', | |
help='timezone to convert to (default JST)', default=JST, type=upper) | |
parser.add_argument('-f', '--format', default = TIME_FORMAT, | |
help='format for output, as strftime format string') | |
args=parser.parse_args() | |
return args | |
def _parse_date(date): | |
pattern = """ | |
(?P<year>\d{4}) | |
(?P<sep>[ ./-])? | |
(?P<month>\d?\d) | |
(?P=sep)? | |
(?P<day>\d?\d) | |
""" | |
if parsed_date := re.match(pattern, date, re.VERBOSE): | |
return list(map(int,parsed_date.group('year', 'month', 'day'))) | |
else: | |
raise ParseError('date', f"couldn't parse {date} into a date") | |
def _parse_time(time): | |
pattern = """ | |
^(?P<hour>\d?\d) | |
(?P<sep>[ .:-])? | |
(?P<minute>\d{2}) | |
((?P=sep)? | |
(?P<second>\d{2}))?$ | |
""" | |
if parsed_time := re.match(pattern, time, re.VERBOSE): | |
return list(map(int, filter(None, | |
parsed_time.group('hour', 'minute', 'second')))) | |
else: | |
raise ParseError('time', f"couldn't parse {time} into a time") | |
def _parse_tz(tz): | |
pattern = """ | |
(?P<sign>[+-]) | |
(?P<hour>\d?\d) | |
(?P<sep>[ .:-])? | |
(?P<minute>\d{2}) | |
""" | |
if parsed_tz := re.match(pattern, tz, re.VERBOSE): | |
return parsed_tz.group('sign', 'hour', 'minute') | |
else: | |
raise ParseError('timezone', f"couldn't parse {tz} into a timezone") | |
def _make_tz(tz): | |
if isinstance(tz, datetime.tzinfo): | |
return tz | |
timezone = TIMEZONES.get(tz) | |
if timezone is None: | |
tz_parts = _parse_tz(tz) | |
hours, minutes = map(int, tz_parts[1:]) | |
if tz_parts[0] == '-': | |
hours = -hours | |
timezone = datetime.timezone( | |
datetime.timedelta(hours=hours, minutes=minutes), name='') | |
return timezone | |
def _parse_datetime(date, time, tz): | |
parts = _parse_date(date) | |
parts.extend(_parse_time(time)) | |
timezone = _make_tz(tz) | |
return datetime.datetime(*parts, tzinfo=timezone) | |
if __name__ == '__main__': | |
args = _parse_args() | |
try: | |
dt = _parse_datetime(args.date, args.time, args.timezone) | |
except ParseError as err: | |
sys.exit(f'ERROR: Invalid {err.item}') | |
tgt = _make_tz(args.tgt) | |
print(dt.astimezone(tgt).strftime(args.format)) |
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