What is the preferred XML processor to use with Python?
Some choices are

minidom 
PyXML 
ElementTree
...

EDIT: I will need to be able to read in documents and manipulate them. I also require pretty print functionality.
I can vouch for ElementTree - it's not a particularly complete XML implementation. It's main strength is simplicity of use of the DOM tree objects. They behave like regular pythonic objects (sequences and dicts) even though their actual implementation is somewhat more complex than appearances might suggest. Of all the XML frameworks ET is the one that you can use to accomplish basic tasks quickly. 
On the other hand if your XML is mostly quite conventional stuff it can do a good job of reading and formatting pretty much any document you throw at it.
Annoying limitations (which appeared not to have been fixed four months ago) is it's wonky support for XML namespaces, lack of Xpath. 
In summary it's fine for basic uses. It will let you get up to speed very quickly. XML gurus will find it lacking.
Preferred Python XML processor