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#56 Cleanup time module
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@astropenguin
astropenguin committed Jul 28, 2023
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"""Azely's time module (mid-level API).
This module mainly provides ``Time`` class for date and time information at a
given location (time information, hereafter) and ``get_time`` function to obtain
time information as an instance of ``Time`` class.
The ``Time`` class is subclass of ``pandas.DatetimeIndex`` and expressed like
``Time(['2020-02-18'], dtype='datetime64[ns, Asia/Tokyo]', freq='D')``.
The ``get_time`` function computes time information in several cases:
(1) Current time (e.g., [2020-01-01 22:32:58+09:00]).
(2) Time range today (e.g., [2020-01-01 00:00, ..., 2020-01-02 00:00])
(3) Time range of given date and length (by query)
In the cases of (1) and (2), special queries, ``'now'`` and ``'today'``, must be
specified, respectively. The ``view`` option specifies a timezone where
time (range) is considered (timezone or location name can be accepted).
In the case of (3), formatted query (e.g., ``'2020-01-01 to 2020-01-05'``)
or natural language-like query can be used (e.g., ``'Jan. 1st to Jan. 5th'``),
where start and end must be separated by ``'to'``. The ``view`` option also works.
Examples:
To get current time in Tokyo::
>>> time = azely.time.get_time('now', view="Tokyo")
To get current time in UTC::
>>> time = azely.time.get_time('now', view="UTC")
To get time range today at ALMA AOS::
>>> time = azely.time.get_time('today', view="ALMA AOS")
To get time range from Jan. 1 to Jan. 5 in 2020 in UTC::
>>> time = azely.time.get_time('2020-01-01 to 2020-01-05', view='UTC')
"""
__all__ = ["Time", "get_time"]


# standard library
from datetime import datetime, timedelta, tzinfo
from functools import partial
from typing import Callable


# dependent packages
from astropy.coordinates import EarthLocation
from astropy.time import Time as ObsTime
from dateutil.parser import parse
from pandas import DatetimeIndex, date_range
from pytz import UnknownTimeZoneError, timezone
from .utils import AzelyError
from .location import get_location

# constants
from .consts import (
DAYFIRST,
HERE,
NOW,
TODAY,
FREQ,
TIMEOUT,
YEARFIRST,
)

DELIMITER = "to"


# data classes
class Time(DatetimeIndex):
"""Azely's time information class."""

def to_obstime(self, earthloc: EarthLocation) -> ObsTime:
"""Convert it to an astropy's time (obstime)."""
return ObsTime(self.tz_convert(None), location=earthloc)

def to_index(self) -> DatetimeIndex:
"""Convert it to a pandas DatetimeIndex."""
return DatetimeIndex(self)

@property
def _constructor(self):
"""Constructor of class."""
return Time


# main functions
def get_time(
query: str = TODAY,
view: str = HERE,
freq: str = FREQ,
dayfirst: bool = DAYFIRST,
yearfirst: bool = YEARFIRST,
timeout: int = TIMEOUT,
) -> Time:
"""Get time information by various ways.
The ``get_time`` function computes time information in several cases:
(1) Current time (e.g., [2020-01-01 22:32:58+09:00]).
(2) Time range of today (e.g., [2020-01-01 00:00, ..., 2020-01-02 00:00])
(3) Time range of given date and length (by query)
In the cases of (1) and (2), special queries, ``'now'`` and ``'today'``, must be
specified, respectively. The ``view`` option specifies a timezone where
time (range) is considered (timezone or location name can be accepted).
In the case of (3), formatted query (e.g., ``'2020-01-01 to 2020-01-05'``)
or natural language-like query can be used (e.g., ``'Jan. 1st to Jan. 5th'``),
where start and end must be separated by ``'to'``. The ``view`` option also works.
Args:
query: Query string (e.g., ``'2020-01-01 to 2020-01-05'``).
If ``'today'`` (by default) or ``'now'`` is specified,
then time range of today or current time is computed, respectively.
view: Name of timezone (e.g., ``'Asia/Tokyo'`` or ``'UTC'``) or location
with which timezone can be identified (e.g., ``'Tokyo'``).
freq: Frequency of time samples as the same format of pandas offset aliases
(e.g., ``'1D'`` -> 1 day, ``'3H'`` -> 3 hours, ``'10T'`` -> 10 minutes).
dayfirst: Whether to interpret the first value in an ambiguous 3-integer
date (e.g., ``'01-02-03'``) as the day. If True, for example,
``'01-02-03'`` is treated as Feb. 1st 2003.
yearfirst: Whether to interpret the first value in an ambiguous 3-integer
date (e.g., ``'01-02-03'``) as the year. If True, for example,
``'01-02-03'`` is treated as Feb. 3rd 2001.
If ``dayfirst`` is also ``True``, then it will be Mar. 2nd 2001.
timeout: Query timeout expressed in units of seconds (see notes).
Returns:
Time information as an instance of ``Time`` class.
Raises:
AzelyError: Raised if the function fails to parse query or timezone.
Notes:
If location is specified as ``view``, then ``azely.location.get_location``
function is used inside the function, which requires internet connection
if the location is queried for the first time.
Examples:
To get current time in Tokyo::
>>> time = azely.time.get_time('now', view="Tokyo")
To get current time in UTC::
>>> time = azely.time.get_time('now', view="UTC")
To get time range of today at ALMA AOS::
>>> time = azely.time.get_time('today', view="ALMA AOS")
To get time range from Jan. 1 to Jan. 5 in 2020 in UTC::
>>> time = azely.time.get_time('2020-01-01 to 2020-01-05', view='UTC')
"""
query = query.strip()

try:
tzinfo = timezone(view)
except UnknownTimeZoneError:
tzinfo = get_location(view, timeout=timeout).timezone

if query.lower() == NOW:
return Time(get_time_now(tzinfo))
elif query.lower() == TODAY:
return Time(get_time_today(freq, tzinfo))
else:
parser = partial(parse, dayfirst=dayfirst, yearfirst=yearfirst)
return Time(get_time_period(query, freq, tzinfo, parser))


# helper functions
def get_time_now(tzinfo: tzinfo) -> DatetimeIndex:
"""Get current time at given timezone."""
start = end = datetime.now(tzinfo)
return date_range(start, end, tz=tzinfo, name=tzinfo.zone)


def get_time_today(freq: str, tzinfo: tzinfo) -> DatetimeIndex:
"""Get time range of today at given timezone."""
start = datetime.now(tzinfo).date()
end = start + timedelta(days=1)
return date_range(start, end, None, freq, tz=tzinfo, name=tzinfo.zone)


def get_time_period(
query: str, freq: str, tzinfo: tzinfo, parser: Callable
) -> DatetimeIndex:
"""Get time range of given date and length at given timezone."""
period = query.split(DELIMITER)

try:
if len(period) == 1:
start = parser(period[0])
end = start + timedelta(days=1)
else:
start, end = map(parser, period)
except ValueError:
raise AzelyError(f"Failed to parse: {query}")

return date_range(start, end, None, freq, tz=tzinfo, name=tzinfo.zone)

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