saving state in Python/CGI

[Frank Gibbons]

Hi,

I've been using Python (and Jython) for about 5 months now. So far, so 
great. I'm building a CGI app that has about 5 different stages, and I need 
to maintain state between them. Specifically, it's a scientific tool that 
requires the user to upload a (possibly quite large) datafile, processes 
it, does some computation, then hands it back (formatted) with results.

I need access to the data on each page, yet don't want to pass it as a 
hidden field, because of its potential size. In Perl, I could just use the 
save() method from CGI.pm to save the form on the server side, pass a 
session key in a hidden field, then retrieve the data using the key. For 
the life of me, I can't find an equivalent way in Python. cgiFormStorage 
looks like a dictionary, but it's immutable, so you can't retrieve data 
from disk and add it to the form. cgi.py appears to have no analog to 
CGI.pm's save() method, at least not that I've been able to find. I've 
tried pickling the form, but that doesn't work either (it saves something 
to disk alright, but not the large data retrieved from a multi-part form 
file upload).

Perhaps I've missed something. Maybe that's just not how you do things in 
Python. Can anyone help?

Thanks,

-Frank Gibbons

PhD, Computational Biologist,
Harvard Medical School BCMP/SGM-322, 250 Longwood Ave, Boston MA 02115, USA.
Tel: 617-432-3555       Fax: 
617-432-3557       http://llama.med.harvard.edu/~fgibbons