newbie xml+python question

[Tigra]

Hi

Please, recommend what to use (and where to get a comprehensive doc) on an
xml library which allows solving these tasks:
1. parse xml into dom (I mean into language specific xml tree struct)
2. roll a dom of my own and save it into xml (also update an existing dom)
3. check dom and/or xml against a dtd file/string/stream (at least string)
4. parse dtd into dom and reverse (I just want to create/parse dtds of my own)
5. transform an xml document with an xsl template.
6. have hooks on every step of operation. I.e. if a dtd validation fails, I'd
   like to get an exceptionm with info on where and why the error occured, not
   just "Validation error at xml line 14 (or node ...)".

I guess that SAX isn't able of meeting all these requrements.
Any help (or even advocacy) is appreciated.

Thanks

Sergey