dgilland / zulu Goto Github PK

Hey Derrick, the docs for zulu still refer to zulu.delta(), but it was deprecated in 0.11.0

Hi, thanks for a great time library.

I'm facing a weird issue. When parsing a datetime string with 31.12 or 30.12 I get the wrong year when formatting as "YYYY"

To reproduce:
`

import zulu
zulu.parse("2019-12-31 00:00:00.000Z").format("YYYY")
'2020'
zulu.parse("2019-12-30 00:00:00.000Z").format("YYYY")
'2020'
zulu.parse("2019-12-29 00:00:00.000Z").format("YYYY")
'2019'
`

Should this really happen?

Due to the way datetime.timedelta is implemented, the zulu.Delta subclass isn't used:

>>> delta = zulu.Delta(seconds=5)
>>> delta + delta
datetime.timedelta(0, 10)
>>> delta - delta
datetime.timedelta(0)
>>> delta / 1
datetime.timedelta(0, 5)
>>> delta // 1
datetime.timedelta(0, 5)
>>> delta * 1
datetime.timedelta(0, 5)

Arrow tokens: https://arrow.readthedocs.io/en/latest/#tokens
Unicode date patterns: http://www.unicode.org/reports/tr35/tr35-19.html#Date_Field_Symbol_Table

I think we can "cheat" a bit and simply map Arrow Unicode tokens to strptime-style tokens. Nothing fancy, perhaps just a simple look-ahead parser that translates things like YYYY-MM-DD into %Y-%m-%d or M/D/YY into %-m/%-d/%y (note that %-m and %-d require glibc installed so may need a more universal way to handle that or simply make note of it as a requirement).

It can lead to confusion between zulu.delta and zulu.Delta since these two have different parameters and handle positional arguments differently. So we'll rename zulu.delta to zulu.parse_delta to make it more explicit.

Allow user to do something like that following:

zulu.parse({'year': 2017, 'month': 2, 'day': 9})
zulu.parse(**{'year': 2017, 'month': 2, 'day': 9})

zulu.parse_delta({'hours': 1, 'minutes': 30, 'seconds': 15})
zulu.parse_delta(**{'hours': 1, 'minutes': 30, 'seconds': 15})

DateTime.days_in_year() --> Should return total number of days in a particular year.

DateTime.days_in_years() --> Should return total number of days in a given years range. For example, DateTime.days_in_years(2016, 2018) should return the total number of days from January 1st 2016 to December 31st 2018.

DateTime.days_in_months() --> Should return total number of days in a given month range. For example, DateTime.days_in_months(2, 5) should return the total number of days from February 1st to May 1st.

DateTime.weeks_in_year() --> We can use isocalendar() and return the number of weeks.

Zulu.add and Zulu.subtract already do this so makes sense for Zulu.shift too behave the same.

Zulu uses the same Unicode date patterns as Babel does but Babel has locale support. Should be a drop-in replacement with the added benefit of supporting a locale option in zulu.DateTime.format().

example from python 3.8

Python 3.8.1 (default, Jan  8 2020, 23:09:20)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.10.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from dateutil import tz

In [2]: import zulu

In [3]: n = zulu.now()

In [4]: n
Out[4]: <Zulu [2020-01-14T22:37:07.389997+00:00]>

In [5]: n.astimezone(tz.gettz("Europe/Paris"))
Out[5]: <Zulu [2020-01-14T22:37:07.389997+00:00]>

In [6]: n.datetime.astimezone(tz.gettz("Europe/Paris"))
Out[6]: datetime.datetime(2020, 1, 14, 23, 37, 7, 389997, tzinfo=tzfile('/usr/share/zoneinfo/Europe/Paris'))

Also tried to update tox in a zulu fork and test branch: all unittests are OK in python 3.7 and less, but not ok in python 3.8:
https://travis-ci.com/ThomasChiroux/zulu/builds/144422588

This may have been related to this python bug:
https://bugs.python.org/issue32417 which has been merged in python 3.8

still investigating...
(a work around could be as seen in the example to call datetime before astimezone and force a cast to datetime before calling astimezone, but it's less powerfull than standard zulu lib (no timezone parsing)

Usage:

dt1 = zulu.create(2017, 1, 1)
dt2 = zulu.create(2017, 1, 2)
dt3 = zulu.create(2017, 1, 1)

dt1.is_before(dt2) is True
dt1.is_after(dt2) is False

dt1.is_on_or_before(dt3) is True
dt1.is_on_or_after(dt3) is True

dt2.between(dt1, dt3) is True
dt1.between(dt3, dt2) is True
dt1.between(dt2, dt3) is False

Should basically call DateTime.shift.

dt.add(hours=5) == dt.shift(hours=5)
dt.add(hours=-5) == dt.shift(hours=-5)

dt.sub(hours=5) == dt.shift(hours=-5)
dt.sub(hours=-5) == dt.shift(hours=5)

Should return the number of days in the current month of the DateTime object.

Can use calendar.monthrange:

>>> from calendar import monthrange
>>> monthrange(2011, 2)
(1, 28)
>>> monthrange(2012, 2)
(2, 29)

DateTime.get_days() --> Should return the total number of days between the given dates. For example, DateTime.get_days('05/23/2016', '06/23/2016') should return you the total number of days between those two dates.

DateTime.get_weeks() --> Same as get_days() but, this returns total number of weeks between the given dates.

DateTime.get_weekday() --> Should return a tuple something like (3, 'Wednesday') when a date is given. For example, DateTime.get_weekday('8/3/2016') should return (3, 'Wednesday') where 3 represents third day in the week.

Basically want to have something that works like this:

dt1 = DateTime(2015, 1, 1)
dt2 = DateTime(2017, 1, 1)

dt1.format_from_now()
# dt1 - now()
#1 year, 7 months ago

dt1.format_to_now()
# now() - dt1
# in 1 year, 7 months

dt1.format_from(dt2)
# dt1 - dt2
#2 years ago

dt1.format_to(dt2)
# dt2 - dt1
# in 2 years

dt2.format_from_now()
# dt2 - now()
# in 4 months

dt2.format_to_now()
# now() - dt2
#4 months ago

dt2.format_from(dt1)
# dt2 - dt1
# in 2 years

dt2.format_to(dt1)
# dt1 - dt2
#2 years ago

Can use babel.dates.format_timedelta.

We need to have similar methods like arrow.Arrow.span_range() and arrow.Arrow.range(). (http://crsmithdev.com/arrow/#ranges-spans)

We have DateTime.naive but would be good to have DateTime.datetime that returns a native datetime object.

To allow zulu.parse to be the universal way to get some kind of zulu object, we can add a flag to zulu.parse that will allow it to parse the input into a zulu.Delta object.

Similar to arrow.span, arrow.floor, and arrow.ceil: http://crsmithdev.com/arrow/#ranges-spans