[AstroPy] Co-ordinating Python astronomy libraries?

Anne Archibald aarchiba@physics.mcgill...
Tue Jul 6 11:39:14 CDT 2010


Hi,

I use a couple of python astronomy libraries; the python bindings to
the pulsar search library PRESTO, and the python bindings to the
FORTRAN library SLALIB. Both were written by Scott Ransom; obviously I
can't speak for his motivations in writing them.

I think I follow a fairly common pattern, though: the libraries I use
are fairly thin wrappers of existing compiled code, and in one case
the code is very domain-specific. So combining them somehow with other
python libraries would involve either linking together a huge mass of
different compiled libraries with overlapping functionality, or
modifying the underlying libraries. Either one would be a tremendous
amount of work.

That said, I use SLALIB for a simple coordinate conversion (in fact I
use it to replicate exactly another coordinate conversion done in
compiled code, so this is kind of theoretical), so in principle if
there were a generic python astronomy library that covered this (I
didn't find one) I might have used it instead. The PRESTO code, not so
much; it includes some extremely specific pulsar searching code that
can't reasonably be included in existing python libraries.

What might be nice would be a "standard" list of data types for common
objects, so that at least one could pass objects from one library to
another. RA and Dec objects, perhaps, or time objects. Of course time
objects would be a massive headache if you wanted them to be
generically usable, since they'd need to be good to the nanosecond
over a span of millenia (so doubles won't cut it), support
UTC/TDB/TAI/etc. as well as MJD/sidereal/GMT/local time
representations... Nevertheless, compiled code (and thin wrappers)
tend to just take doubles and rely on the user to keep track of what
they mean, while a more pythonic and less error-prone approach would
use python's type system to catch many errors.

Anne

On 3 July 2010 18:25, James Turner <jturner@gemini.edu> wrote:
> Thanks for all the replies to my message about co-ordinating libraries.
> I've been wrapped up in SciPy code sprints for the past couple of days
> and now I'm going on vacation for 3 weeks, but I'll have a closer look
> at your libraries and documents and post more as soon as I can. Maybe
> Perry and Mark will also have comments.
>
> It sounds like there's some nice work going on, both filling in
> functionality and documenting it. It will be great if we can get some
> of that into AstroLib or the SciPy pages, or at least link to it from
> there so people can track it.
>
> Thanks a lot :-).
>
> James.
>
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