[AstroPy] POLL: vision for a common Astronomy package

Mark Sienkiewicz sienkiew at stsci.edu
Wed Jul 6 10:21:44 EDT 2011

Ole Streicher wrote:
> Am 05.07.2011 19:45, schrieb Mark Sienkiewicz:
>> If you look in the current astrolib.pywcs, you'll see that it makes use 
>> of a wcs library by incorporating the entire source code of the third 
>> party library.  This is particularly convenient for users because they 
>> can just install the python package and expect it to work.  This is a 
>> way that you can make third party routines available without creating 
>> additional dependencies, though it does involve some work for the 
>> developer.  (But then, that is what developers do, right?  They do some 
>> extra work to make things easier for the user.)
> I am not completely happy with this: On some systems, the
> third-party-package may be already installed, or may be installed with
> the package management system. For pywcs, there are already wcslib
> packages available for Fedora and Ubuntu, so there would be no need to
> install them again -- resolving the dependency is done by the package
> management system. Another point is that one may run into difficulties
> since bug fixes in the original package take some time to find their way
> into the python package.

I often have the opposite problem -- the package that the system 
provides is the one that is older and broken.  For example, every one of 
my Solaris machines already has BLAS installed, and every one of them is 
missing a function that scipy needs.  At times, I've had to make 
difficult hacks to autoconfigs to make it use the copy of some library 
that I provide.

> For this reason, it would be good if there was a choice of using the
> original package in case it is already installed instead of the one that
> was packed with the python package. This would make the life for Linux
> (Ubuntu, Fedora, OpenSUSE) package creators much easier.

If there is an ACTIVE choice made by the user, I agree.  The user could 
choose to use the already-installed package if they need to do that.  
They can also take responsibility for using a library that our python 
code was never tested with.

I would object if there is an automatic detector that prefers the system 
package, primarily because that is a scenario that causes problems for 
me all the time both as a user and as a support engineer.


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