Dynamic Web content and forms processing in Python

From the standard Python library, we need sys for the standard output stream, sys.stdout. We need os for the environmental variable dictionary, os.environ. The string module supplies string.letters and string.digits, from which we pick the cookie's random characters, and the random module randomizes those choices. The gdbm module is the lightweight database that lets us store and retrieve user information. The time module is necessary to determine expiration times.

#================================================================
# Imports
#----------------------------------------------------------------
import sys, os, string, random, gdbm, time

Specific to Web applications are: Cookie module, with handy functions for cookie work; urllib for escaping displayed values; and cgi for obtaining name-value pairs passed to the script. The cgitb module displays a stack traceback in case the script fails; in a production script, you would remove the “cgitdb.enable()” that turns on this traceback feature.

import cgi, urllib, Cookie
import cgitb; cgitb.enable()

The lxml.etree module handles XHTML generation; we import it here as et.

import lxml.etree as et