[Zope] Whats the difference ( Newbie question )

[Rubinstein Fredrik]

	Hi there
<dtml-var "_.str(startdatum[0:4])">  will give me an answer
<dtml-var "_.str(startdatum[5:2])">  will give me nothing

What function do i use to extract a part of a string.
Been looking around a python.org finding everything except the 
function I want.

Cheers

Fred