User:Emily/Prototyping/Trimester 03/03

HTTP server -- programs (CGI scripts) -- interface (user input submitted through HTML<form>or<isindex>element) --> generate web content

python -m CGIHTTPSever

structure of CGI

web server, processes requests via HTTP (Hypertext Transfer Protocol)

process user input submitted through an HTML <FORM> or <ISINDEX> element

cgi_directories [' /cgi-bin', ' /htbin'] containing CGI scripts (server's special cgi-bin directory)

output - CGI script consists of two sections, separated by a blank line.

print "Content-Type: text/html" # header, telling what kind of data is following (HTML is following)
print                                          # blank line, end of headers
print "<TITLE>CGI script output</TITLE>"
print "Hello Morld"  #html, nice formatting

using cgi module

import cgitb
cgitb.enable() # display detailed reports in web browser
cgitb.enable(display=0, logdir="/path/to/logdir") #have the reports saved to files

= to get at submitted form data

FieldStorage class --> can be indexed like a Python dictionary (in operator; support the standard dictionary method keys(), and built-in function len())

form = cgi.FieldStorage()

the following code checks that the fields are set to a non-empty string

 if "***" not in form or "###" not in form:
     print "Error"
     print "please fill in *** and ### fields"
     return
 print "<p>***:", form["***"].value
 print "<p>###:", form["###"].value

if the submitted form data contains more than one field with the same name -->form[key] is not a FieldStorage or MiniFieldStorage instance but a list of such instances; form.getvalue(key) return a list of strings; getlist()method, always returns a list of values

value = form.getlist("username")
usernames = ",".join(value)

If a field represents an uploaded file ????

fileitem = form["userfile"]

The appropriate way to read form data values was to always use the code which checks whether the obtained value is a single value or a list of values.

compact code:

import cgi
form = cgi.FieldStorage()
user = form.getfirst("user", "").upper()    # This way it's safe.
for item in form.getlist("item"):
    do_something(item)

Link: https://docs.python.org/2/library/cgi.html