This is the dulwich project.
It aims to give an interface to git repos that doesn't call out to git
directly but instead uses pure Python.
Open up a repo by passing it the path to the .git dir. You can then ask for
HEAD with repo.head() or a ref with repo.ref(name). Both return the SHA id
they currently point to. You can then grab this object with
repo.get_object(sha).
For the actual objects the ShaFile.from_file(filename) will return the object
stored in the file whatever it is. To ensure you get the correct type then
call {Blob,Tree,Commit}.from_file(filename). I will add repo methods to do
this for you with file lookup soon.
There is also support for creating blobs. Blob.from_string(string) will create
a blob object from the string. You can then call blob.sha() to get the sha
object for this blob, and hexdigest() on that will get its ID.
The project is named after the part of London that Mr. and Mrs. Git live in
in the particular Monty Python sketch. It is based on the Python-Git module
that James Westby <jw+debian@jameswestby.net> released in 2007 and now
maintained by Jelmer Vernooij and John Carr.