[Numpy-discussion] code review for datetime arange

[Robert Kern]

On Thu, Jun 9, 2011 at 16:27, Robert Kern <robert.kern at gmail.com> wrote:
> On Thu, Jun 9, 2011 at 15:01, Mark Wiebe <mwwiebe at gmail.com> wrote:
>> I've replaced the previous two pull requests with a single pull request
>> rolling up all the changes so far. The newest changes include finishing the
>> generic unit and np.arange function support.
>> https://github.com/numpy/numpy/pull/87
>> Because of the nature of datetime and timedelta, arange has to be slightly
>> different than with all the other types. In particular, for datetime the
>> primary signature is np.arange(datetime, datetime, timedelta).
>> I've implemented a simple extension which allows for another way to specify
>> a date range, as np.arange(datetime, timedelta, timedelta). Here (start,
>> delta) represents the datetime range [start, start+delta). Some examples:
>>>>> np.arange('2011', '2020', dtype='M8[Y]')
>> array(['2011', '2012', '2013', '2014', '2015', '2016', '2017', '2018',
>>        '2019'], dtype='datetime64[Y]')
>>>>> np.arange('today', 10, 3, dtype='M8')
>> array(['2011-06-09', '2011-06-12', '2011-06-15', '2011-06-18'],
>> dtype='datetime64[D]')
>
> I would prefer that we not further overload the signature of
> np.arange() for this case. A new function dtrange() that can take a
> delta would be preferable.

Alternately, a general np.deltarange(start, delta[, step]) function
might be useful, too. I know I've done the following quite a few
times, even with just integers:

  np.arange(start, start+delta)

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco