[mod_python] util.Fieldstorage and form

Hi all,
    Other day i was trying to build upload functionality in psp. I am 
handling form(method: POST) submission in psp.
this form contain a hidden element and  a element of type file for upload.
I observed certain things. When I use form['field'] to access value of 
hidden form element,and in same code
if I use FieldStorage(req) to get the attributes of uploaded file. I can't 
access file attributes.

but if I use only FieldStorage to access all the elements of form, I could 
access it.

so why can't I  use both form and FieldStorage in same code?


Thanks
Sandip