ORM recommendation when using "live"/predefined DB?

[Phillip B Oldham]

We're trying to move to Python for a few parts of our application. We
have a live database, which has been modeled for a specific use, and
has other code connecting to and working with it.

We'd like to reduce the amount of work we have to do in terms of
keeping our python code up-to-date with schema changes, and we don't
want python objects to dictate how the database should be structured.

Can you recommend an ORM (or similar) package to look into?