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"""Fill gaps in Python time API-s.
parse_iso_timestamp:
Parse reasonable subset of ISO_8601 timestamp formats.
[ http://en.wikipedia.org/wiki/ISO_8601 ]
datetime_to_timestamp:
Get POSIX timestamp from datetime() object.
"""
import re
import time
from datetime import datetime, timedelta, tzinfo
from typing import Optional, Pattern
__all__ = (
'parse_iso_timestamp', 'FixedOffsetTimezone', 'datetime_to_timestamp',
)
class FixedOffsetTimezone(tzinfo):
"""Fixed offset in minutes east from UTC."""
__slots__ = ('__offset', '__name')
__offset: timedelta
__name: str
def __init__(self, offset: int) -> None:
super().__init__()
self.__offset = timedelta(minutes=offset)
# numeric tz name
h, m = divmod(abs(offset), 60)
if offset < 0:
h = -h
if m:
self.__name = "%+03d:%02d" % (h, m)
else:
self.__name = "%+03d" % h
def utcoffset(self, dt: Optional[datetime]) -> Optional[timedelta]:
return self.__offset
def tzname(self, dt: Optional[datetime]) -> Optional[str]:
return self.__name
def dst(self, dt: Optional[datetime]) -> Optional[timedelta]:
return ZERO
ZERO = timedelta(0)
#
# Parse ISO_8601 timestamps.
#
"""
TODO:
- support more combinations from ISO 8601 (only reasonable ones)
- cache TZ objects
- make it faster?
"""
_iso_regex = r"""
\s*
(?P<year> \d\d\d\d) [-] (?P<month> \d\d) [-] (?P<day> \d\d) [ T]
(?P<hour> \d\d) [:] (?P<min> \d\d)
(?: [:] (?P<sec> \d\d ) (?: [.,] (?P<ss> \d+))? )?
(?: \s* (?P<tzsign> [-+]) (?P<tzhr> \d\d) (?: [:]? (?P<tzmin> \d\d))?
| (?P<tzname> Z ) )?
\s* $
"""
_iso_rc: Optional[Pattern[str]] = None
def parse_iso_timestamp(s: str, default_tz: Optional[tzinfo] = None) -> datetime:
"""Parse ISO timestamp to datetime object.
YYYY-MM-DD[ T]HH:MM[:SS[.ss]][-+HH[:MM]]
Assumes that second fractions are zero-trimmed from the end,
so '.15' means 150000 microseconds.
If the timezone offset is not present, use default_tz as tzinfo.
By default its None, meaning the datetime object will be without tz.
Only fixed offset timezones are supported.
"""
global _iso_rc
if _iso_rc is None:
_iso_rc = re.compile(_iso_regex, re.X)
m = _iso_rc.match(s)
if not m:
raise ValueError('Date not in ISO format: %s' % repr(s))
tz = default_tz
if m.group('tzsign'):
tzofs = int(m.group('tzhr')) * 60
if m.group('tzmin'):
tzofs += int(m.group('tzmin'))
if m.group('tzsign') == '-':
tzofs = -tzofs
tz = FixedOffsetTimezone(tzofs)
elif m.group('tzname'):
tz = UTC
return datetime(
int(m.group('year')), int(m.group('month')), int(m.group('day')),
int(m.group('hour')), int(m.group('min')),
m.group('sec') and int(m.group('sec')) or 0,
m.group('ss') and int(m.group('ss').ljust(6, '0')) or 0,
tz
)
#
# POSIX timestamp from datetime()
#
UTC = FixedOffsetTimezone(0)
TZ_EPOCH = datetime.fromtimestamp(0, UTC)
UTC_NOTZ_EPOCH = datetime.utcfromtimestamp(0)
def datetime_to_timestamp(dt: datetime, local_time: bool = True) -> float:
"""Get posix timestamp from datetime() object.
if dt is without timezone, then local_time specifies
whether it's UTC or local time.
Returns seconds since epoch as float.
"""
if dt.tzinfo:
delta = dt - TZ_EPOCH
return delta.total_seconds()
elif local_time:
s = time.mktime(dt.timetuple())
return s + (dt.microsecond / 1000000.0)
else:
delta = dt - UTC_NOTZ_EPOCH
return delta.total_seconds()
|
