How do I distinguish a string from a sequence?

[asgard]

> > A quick check on my system of 1.5.2 through 2.1.1 doesn't have
> > a StringTypes list in the types module (although it could of course
> > just be defined locally if not present).
> 
> Certainly no version of Python before Unicode was introduced would have it.

I am using 2.2a3 documentation and it's not written there (in types
module). 

Regards, Jan Samohyl