HTML Parser which allows low-keyed local changes?

[Robert]

I tried lxml, but after walking and making changes in the element 
tree, I'm forced to do a full serialization of the whole document 
(etree.tostring(tree)) - which destroys the "human edited" format 
of the original HTML code.
makes it rather unreadable.

is there an existing HTML parser which supports tracking/writing 
back particular changes in a cautious way by just making local 
changes? or a least tracks the tag start/end positions in the file?


Robert