Train rides can be good - if not creativity, then at least boredom-induced productivity. I had planned to make a hgapi fork that worked against git instead of Mercurial, and during the ride back from holding a Python workshop in Malmö (a three-hour trip back to Karlskrona; I still have another hour to go...), I finally did. gitapi is born, and even though its in it's infancy, it supports a large number of common operations. Fair warning - I basically just swiched hg->git and then fixed the test cases that still made sense, so there's bound to be some kinks left to iron out. Either way, the test suite passes on both Python 2.7 and 3.2, so there's something.
hgapi is a pure-Python API to Mercurial, that uses the command-line interface instead of the internal Mercurial API. The rationale for this is twofold: the internal API is unstable, and it is GPL.