These are chat archives for astropy/astropy

26th
May 2014
Erik Tollerud
@eteq
May 26 2014 17:45
@astrofrog @embray or anyone else who might know… How do I look at what command-line options are available for astropy-helpers ?
specifically what I want to do is be able to tell ah_bootstrap to not automatically update the submodules...
Wolfgang Kerzendorf
@wkerzendorf
May 26 2014 18:55
while we are on astropy-helpers (great job by @astrofrog and @embray!), is there an easy way to add further custom options to AstropyTest?
Ghost
@ghost~53638049048862e761fa0380
May 26 2014 19:35
@eteq - it seems to me like sc = SkyCoord(..); sc.represent_as() should return a new SkyCoord using that representation. Instead it returns an instance of the requested representation class. This kind of ties in with the SunPy desire to swap between representations easily for a given frame.
Erik Tollerud
@eteq
May 26 2014 19:37
@taldcroft - the idea is to use represent_as consistently everywhere as a way to get a new representation. It’s also absolutely not a good idea to “swap between representations” - a frame gets one preferred representation, but it caches the transform, so if you do someframeorskycoord.represent_as(SphericalRepresentation) twice, the second time is very fast
So which one is the “true” representation is essentially arbitrary - this is why the data attribute on frames was originally private, but someone complained about that
I’m certainly game for changing the name of represent_as if you have a better suggestion, though.
Ghost
@ghost~53638049048862e761fa0380
May 26 2014 19:43
I guess the question is how to easily change how a coordinate object displays itself for repr or str. I have a SkyCoord defined in ICRS but now I want make that into a coordinate object that shows in cylindrical.
Erik Tollerud
@eteq
May 26 2014 20:33
Actually, that’s what I thought was part of your plan for SkyCoord - to have something like Time’s format, which controlled how it was displayed while using the same underlying frame class
It’s possible I’m missing some key use case, but it’s just not clear to me when you sould want to have some stageful way to change which is the “current” representation for something that’s still in the same frame, given that it’s simple enough just to do represent_as if the default isn’t your cup of tea