Let to_python (in custom db field) know the connection being used in multi-db environment

[liangent]

get_prep_* methods have get_db_prep_* now. What about to_db_python, or adding another argument to to_python?

[Russell Keith-Magee]

get_prep_value *doesn't* take a connection argument, because it is the connection-agnostic portion of data preparation. get_preb_db_value *does* take a connection argument, because it represents the connection-specific data transformation.

to_python should also be connection-agnostic -- as evidenced by the fact that it is often invoked by get_prep_value. It's also used by serializers and form handlers, both of which are connection agnostic.

In short, there's no reason that to_python should need a connection argument.

As for adding to_db_python -- why is this method required? The fact that Django's fields work fine without needing a database-side to_python implementation is pretty strong evidence that such a method isn't required. We're not going to add a method "just because" -- there needs to be a use case.