Hi Pierre,
Glad you liked it, feel free to integrate the error formatting and 
possibly the plot data reshaping to Kappy, this would allow me to remove 
the code from topkappy.
The reshaping of the plot_data is advantageous for people using e.g. 
Matplotlib, but other people may prefer the original format. The 
computing time is simply proportional to the number of data points - it 
takes 233ms to reshape 100 lists of 100k values on a good computer, to 
give you an idea. I don't think this is much time compared to the 
duration of the simulation that would generate the data.
I also got a message from John Bachman pointing me to PySB. It looks 
like something I could have used but I didn't find it at the time. One 
advantage of Kappy is that it automatically installs Kappa, which makes 
it a very friendly dependency. PySB could benefit from that (right now 
you need to install Kappa by hand to use it).
Cheers,
Valentin