Using CGI in web interfaces

Presenter Notes

We have learned how to use CGI to run Python code on a web server to generate HTML on the fly
This saves us the step of creating the HTML code as a separate file beforehand
Example CGI scripts
- View source of CGI script
- View output of CGI script
You can do quite a bit more with CGI scripts

HTML forms use different tag names to represent input types
- radio, text, checkbox, ...
- These tags have two key parameters that identify the part of the form (name) and the selection (value)
- A special submit button is used to pass the data to a CGI script identified by the action attribute in a form tag
For more info on HTML forms, see the CS 110 lecture on forms
CGI programming in python
- the cgi library has a method called cgi.FieldStorage() that includes a dictionary mapping form tag names to the values selected by users

Google Chart Tools can handle only so much data at a time
Data over 100Kbytes, or a few thousand lines of code, can generate noticeable lag
Sending all your data in the browser to render graphs can be inefficient
Using an HTML form to select the subset of data to graph is a good workaround

The Google controls and dashboards allow users to select subsets of data, which then dynamically update the graphs accordingly
- This is very cool
- This is an example of AJAX (Asynchronous JavaScript and XML)
- Want to learn more about this? Take CS 304 Spring 2013
We are limited to what can be supported by Google's AJAX library
- Using a form to filter before sending data to Google Chart Tools may be your only option