I'd suggest starting with an examination of the existing plugins and inx files int he extensions directory and start with one close to what you want to do.
I'm not sure about calling the export png function from, python, the the remainder is just manipulation of the DOM tree. If you have done any web/javascript work it should be pretty clear.
You said you checked out the wiki. The pages there to reference are: http://wiki.inkscape.org/wiki/index.php/ScriptingHOWTO http://wiki.inkscape.org/wiki/index.php/PythonEffectTutorial http://wiki.inkscape.org/wiki/index.php/MakingAnINX
And some external sites with a couple good tips are: http://ospublish.constantvzw.org/tools/inkscape-plugins-in-python (nice simple example) http://www.kickban.net/?p=36 (good step by step for creating objects)
Also, keep referring back to the answers section at launchpad as there are a few extension related questions and answers there: https://answers.launchpad.net/inkscape (search for extension)
Hope that helps,
-Rob A> 2009/4/27 Rubén Quiñones wrote:
As I don't Know python language (I program in C/C++/vba) , May anyone guide me where I could get examples for that?
I've just looked for in the inkscape wiki, but I'm a bit lost.
Thanks for your time