This is how you export a csv file and get the browser to recognize that its a csv file and popups the download window with web.py. Lets say we have a database with a table called users and you want to create a csv file that contains all the users with their names and id's here is how you do it.
class export: def GET(self): i = web.input() users = web.select(’users’, vars=locals()) csv =  csv.append(”id,name\n“) for user in users: row =  row.append(user.id) row.append(user.name) csv.append(”,“.join(row)) web.header(’Content-Type’,’text/csv‘) web.header(’Content-disposition’, ’attachment; filename=export.csv‘) print "".join(csv) return
I export the csv file in a GET method of a class called export which i map in the urls list to '/export','export'
A quick breakdown, do a database query and iterate over the IterBetter object create a row and appending a comma seperated string to the csv list. Then at the end you send the appropirate HTTP headers , the first telling the type of the file and the second setting the filename and extension.