An introduction to PyObjC describes the general method for translating Objective-C calls into Python calls, including the handling of pass-by-reference arguments and buffers.
This document describes where the PyObjC bindings for this framework are different from the general rule, such as mentioning APIs that are not supported or where the interface is different than expected.
When you’re running on MacOSX 10.4 PyObjC will automaticly translate Python attribute access in KVO access to the underlying NSManagedObject. This functionality no longer works on MacOSX 10.5, you have to use proper KVO methods to access properties to be compatible with both OSX 10.4 and 10.5.
The methods setObservationInfo: and observationInfo cannot be used from Python.