[Zope] How to call functions in DTML?

[Patrick Price]

Simple question from a stupid newbie.

I'm used to writing inline code using PHP and I just want a random 
number to appear on a web page.  
Once I clear that hurdle,  I want to use that number to reference 
different images (objects, right).  
Then I'll have a web page that displays random images from my image library.

How do I call Python functions from within a web (aka DTML Document?) 
page in Zope?

If you tell me to read the documentation I'll strangle you. :-)  It's 
lacking.

Thanks in advance,

-Patrick Price