[mod_python] Upload progress indicator shows after upload?

Essentially this is what I have setup for my upload script:

[code]

#HTML Stuff here
#Declare variables etc...

    while bytes_left >= 0:
            fileData = req.form['filename'].file.read(1024)
            filebuffer = filebuffer + fileData
            bytes_left = bytes_left - 1024
            bytes_read = bytes_read + 1024
            percent = bytes_read/int(length) * 100

#Some nested IF statements to display a progress indicator using images 
based on the percent variable.

[/code]

This is contained in my upload.py in the function upFile which is called 
from the POST method. However, It seems that the file uploads completely 
first and then it will show the progress indications afterwards. However 
this doesn't seem to be logically what my code should be doing. I'm 
somewhat new to mod_python but not python in general, any suggestions?