Passing parameters via URL

[Colin Meeks]

I've written some code that produces a web page.  I have the same code
replicated several times, with small changes that I use throughout a site.
How can I bring these all into one program so I can make a call like

    http://www.xyz.com/program.py?dothis

or

    http://www.xyz.com.program.py?dothat

and have the Python program determine what to do when it receives either
dothis or dothat.

Thanks.

Colin