Re: [matplotlib-devel] XML

[Jack D. <ja...@pe...>]

On Fri, Feb 25, 2005 at 02:04:57PM -0500, Abraham Schneider wrote:
> Hmm.. you make good points. Generally I think it is better to keep 
> everything within python when possible (plus I am not a big fan of 
> XML..). I suspect in the end this ends up being a preference issue, but 
> here is the advantage I see with XML. Suppose I have code that reads 
> data from a file, and can display that data in several different views 
> (e.g. different variables, different outlays, etc. depending on what is 
> being examined). In the past I have written a seperate python program 
> per view that I need or allowed command line parameters to be passed.
> 
> The difficulty with having separate python programs:
> * Will have to either:
>    + run a different program per view I want
>    + pass a python program as a parameter to run (I don't want to have 
> to edit the main program for each new view have another import .. I 
> suppose one could put them all in the same directory, but this could be 
> a hassle for quick hacks). This isn't a big deal, since I've essentially 
> already advocated this for the config files. Somehow the semantics of 
> doing so under these circumstances seems different to me, and perhaps 
> more userfriendly to provide a layout language.
>    + continually reedit the same file with different parameters
> 
> On the other hand, if everything is passed on the command line, I have 
> found it is difficult to get enough specifity to plot exactly I want, 
> without requiring several lines worth of parameters.
> 
> So I see XML as a means of separating the layout of the data and 
> managing the different views, without having to touch the code at all. 
> In the end it doesn't really provide anything new, except for a 
> different method of doing the same thing.
> 

Python imports don't have to be static, you can access modules dynamically
just like you would XML files.  For our web application we keep per-client
information in .py files that gets __import__'d to modify the look & feel,
setup default email addresses, etc.  The modules just have to have some
agreed on names.  If they have a particular function it gets called with
an object they can tweak.

ex/

def apply_custom(client_id):
  try:
    custom = __import__('client_%d' % (client_id))
  except ImportError: # nothing custom
    return

  def NOP(*args): return # do nothing function

  getattr(custom, 'alter_skin', NOP)(skin_object)
  getattr(custom, 'add_reports', NOP)(report_list)
  # etc

The upshot is that you can use python modules just like you would
use XML.  They both contain markup, just different kinds.

-Jack