datestuff 0.3.0
Stuff for dates
License: MIT
Keywords: dates,datetime

=========
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:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.