doubledate.daysfrom#

doubledate.daysfrom(frequency: str, dates=None, *, calendar=None)#

Returns an efficient iterator that yields the number of days since the start of a given frequency.

Parameters:

  • dates (datetime, iterable, optional) – either a date or an iterable of dates

  • calendar (iterable) – iterable of dates to use as custom calendar

  • frequency (str) – one of YS, HS, TS, QS, MS, WS

Notes

Warning

If given a calendar and no dates, the function returns a date-map, mapping each date of the custom calendar to its position within the frequency.

If given a set of dates and no calendar, the function returns the number of days from the generic start of the frequency.

If given a set of dates and a custom calendar, the function returns the number of days since the start of the frequency using the custom calendar as the reference.

Examples

>>> daysfrom(datetime.date(2020,2,29), "MS")
28
>>> daysfrom(datetime.date(2020,2,29), "QS")
59

>>> dates = [datetime.date(2020,1,1) + datetime.timedelta(i) for i in range(90) if i % 12 != 0]
>>> for date, position in zip(dates, daysfrom(dates, "MS")):
...     print(date, position)
2020-01-02, 0
2020-01-03, 1
...
2020-02-29,26
2020-03-02,0
...
2020-03-30,26