Re: [matplotlib-devel] XML

[Abraham S. <ab...@cn...>]

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.

Abe

John Hunter wrote:

>My initial response to something like this, which I've seen before in
>the context of mpl, is: what is the advantage of using a XML over
>python?  Except for the plot command, which specifies a read data and
>filename, everything is pretty much a literal translation of python.
>My suggestion would be to create custom python classes that build your
>figures, and use python 
>
>class PlotItem:
>   def __init__(self, fn, fname, var, color, lw): 
>      ... do something with it
>
>class SubplotItem:
>   def __init__(self, title, pos)
>   ....contains one or more plot items
>
>class FigureItem:
>   def __init__(self, title)
>   ... contains one or more axes items
>
>   
>fig = FigureItem(title="Hodgkin and Huxley cell")
>sub = SubplotItem(title="voltage" pos="1,1")
>fig.add_subplot(sub)
>plot = PlotItem(fn="readData" file="sim.dat", var="voltage")
>sub.add_plot(fig)
>
>and so on.  Then you have the full power of python to specify your
>configuration layer.  What does an XML layer buy you?  I could see
>it's usefulness if you were trying to develop a GUI tool to edit and
>configure your figures....
>
>There has been some interest in having a way to save a figure state to
>an external file and open it where you left off.  An XML
>representation might be useful there, in that it would ease the
>development of figure editors in a way that a pickled version would
>not.
>
>
>    Abraham> p.s. I've had the traits-based config library almost done
>    Abraham> for a bit .. I just haven't had time to put the last
>    Abraham> finishing touches on it. I'll email it soon.
>
>Great.
>
>
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