Python is reference counted. This was happening because you didn't increment the reference count for python objects you were referencing from C++. Your RAII should increment/decrement reference counts on the object, not place objects into a global dict. That's the "correct" way to reference python objects.
Python's GC doesn't scan memory in the same way other languages do. Instead, it detects cycles between python objects. As long as you follow the reference counting rules correctly, you shouldn't have to worry about it. (Unless you need to detect cycles involving your C++ objects.)
