Source code for bag.time

"""Functions to make it easier to work with datetimes.

By the way, some ways of constructing a datetime instance::

    datetime.now()    -> datetime(2015, 7, 17, 2, 18, 39, 255470)
    datetime.now(utc) -> datetime(2015, 7, 17, 5, 18, 39, 255497, tzinfo=<UTC>)
    datetime.utcnow() -> datetime(2015, 7, 17, 5, 18, 39, 255543)
"""

import json
from datetime import datetime, timedelta, tzinfo
from decimal import Decimal
from time import sleep
from typing import Optional
from pytz import timezone
utc = timezone('utc')


[docs]def now_with_tz() -> datetime: """Like datetime.utcnow(), but including tzinfo.""" return datetime.now(utc) return utc.localize(datetime.utcnow())
[docs]def naive(dt: datetime) -> datetime: """Remove the timezone from a datetime instance.""" return datetime(dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.microsecond)
[docs]def parse_iso_datetime(text: str) -> datetime: """Convert the given string to a naive (no tzinfo) datetime.""" text = text.strip() if 'T' in text: sep = 'T' elif ' ' in text: sep = ' ' else: sep = '' DATE_FMT = "%Y-%m-%d" if not sep: return datetime.strptime(text, DATE_FMT) elif len(text) == 16: return datetime.strptime(text, DATE_FMT + sep + '%H:%M') elif len(text) == 19: return datetime.strptime(text, DATE_FMT + sep + '%H:%M:%S') else: TIME_FMT = "%H:%M:%S.%f" suffix = 'Z' if text.endswith('Z') else '' fmt = DATE_FMT + sep + TIME_FMT + suffix return datetime.strptime(text, fmt)
[docs]def simplify_datetime(val: datetime, granularity: str='minute') -> datetime: """Notice this throws away any tzinfo.""" if granularity == 'hour': return datetime(val.year, val.month, val.day, val.hour) elif granularity == 'minute': return datetime(val.year, val.month, val.day, val.hour, val.minute) elif granularity == 'second': return datetime( val.year, val.month, val.day, val.hour, val.minute, val.second) else: raise RuntimeError('granularity not implemented: "{}"'.format( granularity))
[docs]def timed_call(seconds, function, repetitions=-1, *a, **kw): """Perform some task every x seconds. Sleep if necessary. Do not sleep after the last turn. By default, runs forever. To control the number of times that *function* should run, pass in a number of *repetitions*. Returns immediately if *repetitions* is zero. """ period = seconds if isinstance(seconds, timedelta) else \ timedelta(0, seconds) turn = 0 while True: if turn == repetitions: return if repetitions > -1: turn += 1 started = datetime.utcnow() function(*a, **kw) took = datetime.utcnow() - started if turn != repetitions and took < period: sleep((period - took).total_seconds())
[docs]class DJSONEncoder(json.JSONEncoder): """JSON encoder that outputs dates and decimals. Example usage:: DJSONEncoder().encode([datetime.datetime.now()]) '["2015-01-21T14:42:28"]' """
[docs] def default(self, obj): if hasattr(obj, 'isoformat'): return obj.isoformat() elif isinstance(obj, Decimal): return float(str(obj)) else: return super(DJSONEncoder, self).default(obj)
[docs]def dumps(value): """Like json.dumps, but using DJSONEncoder.""" return json.dumps(value, cls=DJSONEncoder)
[docs]def djson_renderer_factory(info): """Pyramid renderer. Install like this:: config.add_renderer('djson', 'bag.time.djson_renderer_factory') """ def _render(value, system): request = system.get('request') if request is not None: response = request.response ct = response.content_type if ct == response.default_content_type: response.content_type = 'application/json' return dumps(value) return _render
[docs]def now_or_future( dt: Optional[datetime], timezone: tzinfo=utc, now: Optional[datetime]=None, ) -> datetime: """If given datetime is in the past, default to now. Given a datetime, returns it as long as it is not in the past; otherwise, returns now. You may pass the ``timezone`` instance for the comparison (defaults to UTC); this is useful if your datetime is naive. The argument ``now`` should be ignored; it is used only in the unit tests. """ now = now or datetime.now(timezone) assert isinstance(now, datetime) if not dt: return now assert isinstance(dt, datetime) if dt.tzinfo is None: # dt is a naive datetime (no timezone) now = naive(now) # comparison only works with another naive datetime return now if dt < now else dt