=========
datestuff
=========
For when you need some :code:`datetime` helpers but not a complete replacement for the modules.
Why?
====
Frankly, I love the built in :code:`datetime` module. Almost everything I need to do, I can just do with it.
However, a few things tend to creep up datetime and datetime again. Things like:
* Creating a range of dates
* Creating an unfixed date
* Checking if two datetimes are within a certain delta of one another
Here's a short look at what's included.
RelativeDate and RelativeDateTime
=================================
These allow you to create an unfixed :code:`date` or :code:`datetime` instance by providing a :code:`timedelta` offset and/or factory method.
By default, :code:`RelativeDate` uses :code:`date.today` and :code:`RelativeDateTime` uses :code:`datetime.now` as the default factories and both have a default offset of :code:`timedelta(0)`:
.. code-block:: python
rd = RelativeDate()
rd.as_date() # date(2016, 7, 24)
rdt = RelativeDateTime()
rd.as_datetime() # datetime(2016, 7, 24, 12, 29)
However, it is also possible to provide other factories as well:
.. code-block:: python
import arrow
rdt = RelativeDateTime(clock=arrow.utcnow)
rdt.as_datetime() # <Arrow [2016-07-24T17:34:58.970460+00:00]>
And as long as the underlying factory produces a :code:`date` or :code:`datetime` compatible object, everything will *just work*. By compatible, I mean implements the :code:`date` or :code:`datetime` interface.
Additionally, if only a static offset from today or now is desired, you can simply provide the offset argument with a :code:`timedelta` or dateutil :code:`relativedelta`. Note that currently, :code:`timedelta` and :code:`relativedelta` are not interoperable.
.. code-block:: python
from datetime import timedelta
rd = RelativeDate(offset=timedelta(days=6))
rd.as_date() # date(2016, 7, 30)
:code:`RelativeDate` and :code:`RelativeDateTime` also allow comparing against regular :code:`date` and :code:`datetime` instances with the standard operators (==, !=, >, etc). Making these incredibly useful for quickly defining date boundaries that are defined statically (such as in a serializer or ORM model):
.. code-block:: python
from datetime import timedelta, date
rd = RelativeDate(offset=timedelta(days=7))
assert rd > date.today() # always true
Adding and subtracting relative instances actually operate on their offsets, rather than underlying :code:`date` or :code:`datetime` values.
.. code-block:: python
from datetime import timedelta
rd = RelativeDate(offset=timedelta(days=1))
rd + rd == RelativeDate(offset(timedelta(days=2)))
rd - rd == RelativeDate()
Some alternate constructors are provided where it makes sense, each allows passing an offset but defaults to :code:`timedelta()`, provided are:
* :code:`RelativeDate.today`: the default constructor
* :code:`RelativeDateTime.now`: the default constructor, allows passing a tzinfo object to the factory
* :code:`RelativeDateTime.utcnow`: factory produces UTC-based datetimes (note: these are NAIVE as it relies on the underlying :code:`datetime.utcnow`)
* :code:`RelativeDateTime.today`: the default constructor, does not allow passing a tzinfo object
For convenience sake there are also truly static constructors:
* :code:`RelativeDate.fromdate`: hoists a regular date into relative context
* :code:`RelativeDateTime.fromdatetime`: hoists a regular datetime into
* :code:`RelativeDateTime.fromdate`: hoists a date into a :code:`RelativeDateTime` context, allows passing a tzinfo object, factory looks like :code:`datetime.combine(the_date, time(tzinfo=tzinfo))`
Any additional static constructors, such as :code:`datetime.strptime`, can be derived from these if truly needed.
.. code-block:: python
from datetime import date, time, timedelta
rd = RelativeDate.fromdate(date(2016, 7, 24), offset=timedelta(days=7))
rd.as_date() # date(2016, 7, 31), always
Finally, any functionality not implemented directly in the relative instance is proxied to the underlying :code:`date` or :code:`datetime` instance.
DateRange
=========
A range of dates is another tool I find myself needing from time to time, however eager creation can sometimes be very expensive for a large range.
Instead, :code:`DateRange` is modeled after the Python 3 :code:`range` type, which has fast path lookup for membership, lazy iteration, indexing and slicing (slices return new :code:`DateRange` objects)
.. code-block:: python
from datestuff import DateRange
from datetime import date, timedelta
dr = DateRange(start=date(2016, 1, 1), stop=date(2016, 12, 31), step=timedelta(days=7))
date(2016, 1, 8) in dr # true
len(dr) # 53, yes this is correct
list(dr) # [date(2016, 1, 1), date(2016, 1, 8), ...]
dr[1] == date(2016, 1, 8) # True
dr[1:-1:2] == DateRange(date(2016, 1, 8), date(2016, 12, 30), step=timedelta(days=14)) # True
:code:`DateRange` also allows creating an open ended range by simply omitting the stop argument. In this case, the only functionality that will not work is using :code:`len` and negative indexing/slicing (as there is no end)
Currently, :code:`DateRange` does not support :code:`relativedelta` as under the hood it uses :code:`timedelta.total_seconds` for Python 2 and 3 compatiblity. This could be resolved in the future, but is unlikely. :code:`DateRange` is, however, compatible with :code:`date` and :code:`datetime` like objects and other :code:`timedelta` like objects. Interestingly, this would apply to :code:`RelativeDate` and :code:`RelativeDateTime` as well.
utils
=====
Currently, the only util is :code:`within_delta` which is useful for comparing two :code:`date` or :code:`datetime` (or like) instances within a certain delta.
.. code-block:: python
from datetime import datetime, timedelta
from datestuff import within_delta
d1 = datetime.now()
d2 = datetime.now()
d1 == d2 # false
within_delta(d1, d2, timedelta(seconds=1)) # true
If simple boundary checking is needed, this tool is much more light weight than either :code:`DateRange` or :code:`RelativeDate`. Sadly, this is another tool that cannot interoperate with :code:`relativedelta` as it and :code:`timedelta` are unorderable (at least in Python 3).
The MIT License (MIT)
Copyright (c) 2016 Alec Nikolas Reiter
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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