On Fri, Apr 11, 2014 at 4:58 PM, Stephan Hoyer <sho...@gmail.com> wrote:
> On Fri, Apr 11, 2014 at 3:56 PM, Charles R Harris < > charlesr.har...@gmail.com> wrote: > >> Are we in a position to start looking at implementation? If so, it would >> be useful to have a collection of test cases, i.e., typical uses with >> specified results. That should also cover conversion from/(to?) >> datetime.datetime. >> > yup -- tests are always good! Indeed, my personal wish-list for np.datetime64 is centered much more on > robust conversion to/from native date objects, including comparison. > A good use case. > Here are some of my particular points of frustration (apologies for the > thread jacking!): > - NaT should have similar behavior to NaN when used for comparisons (i.e., > comparisons should always be False). > make sense. > - You can't compare a datetime object to a datetime64 object. > that would be nice to have. > - datetime64 objects with high precision (e.g., ns) can't compare to > datetime objects. > That's a problem, but how do you think it should be handled? My thought is that it should round to microseconds, and then compare -- kind of like comparing float32 and float64... > Pandas has a very nice wrapper around datetime64 arrays that solves most > of these issues, but it would be nice to get much of that functionality in > core numpy, > yes -- it would -- but learning from pandas is certainly a good idea. > > from numpy import datetime64 > from datetime import datetime > > print np.datetime64('NaT') < np.datetime64('2011-01-01') # this should not > to true > print datetime(2010, 1, 1) < np.datetime64('2011-01-01') # raises exception > print np.datetime64('2011-01-01T00:00', 'ns') > datetime(2010, 1, 1) # > another exception > print np.datetime64('2011-01-01T00:00') > datetime(2010, 1, 1) # finally > something works! > > now to get them into proper unit tests.... -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov
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