Kenneth Gonsalves

Python is a scripting language which is rapidly taking the world by storm. It runs on

all platforms. Don’t worry if you don’t know python - any reasonably competent

programmer can learn python in a day. This tutorial deals with creating 'quicky' dynamic

web pages using python.

You need:

1. Python preferrably version 2.3: http://www.python.org

2. Cheetah ver 0.9.15 or later: http://www.CheetahTemplate.org

3. A text editor (or use idle, the IDE that comes with python)

4. An HTML editor (Quanta plus is a good choice)

5. A browser to view your pages

6. An HTTP server to test your application (Apache?)

We will be creating a simple user registration form. The coding is in two parts:

1. Create a template in html

2. Create a script in Python to populate the template and read and

validate data from it

We will also be following the three fundamental principles of Web programming:

1. Don’t put HTML in your code.

2. Don’t put code in your HTML.

3. Don’t use JavaScript for validation

The registration form will need the following details:

1. Salutation: Mr, Ms, Dr and Mrs - radiobuttons

2. Name: leading and trailing spaces and non-alphanumeric characters not

allowed

3. Interests: Checkboxes

4. City: List select

Here is a screenshot of the running application:

HEIGHT="399">

 

 

Here is the complete Python code:

(remember that indentation is part of the python syntax and the script will not run if

the indentation is changed). Note that the code can be condensed a lot, but I have made it

verbose so that it is self-explanatory

registration.py:

#######################################

#!/usr/bin/python #put your path to python

from Cheetah.Template import Template

import cgi

#to get meaningful error messages

import cgitb

cgitb.enable()

ok = False

msg = ''

theform = cgi.FieldStorage()

#this records the form output

parms = {'name':'','sal':'','city':'','interest':<>,'title':'Registration Form'}

sals = {'Mr':'checked','Ms':'','Dr':'','Mrs':''}

cities = {'Bangalore':'selected','Chennai':'','Mumbai':''}

interests = {'Girls':'','Boys':'','Music':'','Loafing':''} #none selected

if theform.has_key('name'):

        parms<'name'> =

theform.getfirst('name').strip()

        #strip() removes leading and trailing spaces

        ok = True

        #if the name is there the form is complete

        for ch in parms<'name'>:

            if ch in

"!@#$%^&*()<>.,/\+-=":

                msg

+= " Illegal Character: "+ch+', '

                ok

= False

       if theform.has_key('interest'):

            parms<'interest'> =

theform.getlist('interest') #this is a list

            #check the selected

interests

            for k in

interests.keys():

                        if

k in parms<'interest'>:

                            interests

= 'checked'

                       else:

                               interests

= ''

        parms<'sal'> = theform.getfirst('sal')

        #check the selected salutation

        for k in sals.keys():

                    if

k == parms<'sal'>:

                        sals

= 'checked'

                    else:

                        sals

= ''

parms<'city'> = theform.getfirst('city')

#select the selected city

       for k in cities.keys():

                if

k == parms<'city'>:

                        cities

= 'selected'

                else:

                        cities

= ''

if ok:

#save it or mail it or do something with it

        msg = 'Success: '+str(parms<'sal'>)+'

'+str(parms<'name'>)

        msg = msg +' City: '+str(parms<'city'>)+'

Interests: '

        for k in parms<'interest'>:

                    msg

= msg +' '+str(k)

#simplest way to create a cheetah template object

t = Template(file = 'registration.tmpl')

#add the variables to the template object

t.parms = parms

t.msg = msg

t.sals = sals

t.cities = cities

t.interests = interests

#output the template

print "Content-Type: text/html\n\n"

print t

######################################################

Here is the html template: href="https://www.ciol.com/images/content/2004/registration1.htm">registration.html:

#######################################################

#for $r in $sals

#end for

#for $cit in $cities

="">$cit

#end for

#for $ch in $interests

#end for

###########################################

Note:

Copy both registration.py and registration.tmpl into the cgi-bin directory of your Web

server. Make registration.py executable and access it from your browser:

http://localhost/cgi-bin/registration.py

The comments in the python code are self explanatory. We create lists of salutations,

cities and interests and pass them to the template. Template commands start with '#' sign

and template variables passed are identified by a leading '$' sign. This makes it easy for

the html designer to prettify his Web page without knowing anything about coding. You can

view the template file with the preview mode of your html editor which will show you the

relationship between the variables and the html code.

Play around with the code a bit and you'll see how to customise it or add new

components. Enter illegal characters in the 'Name' field to see how validation works. Note

how everything you enter is retained in the form.

The code is copylefted under the KGL (which means you can do whatever you want with it

as long as you dont blame me.

Mail me at lawgon at thenilgiris dot com with doubts, comments and flames.