I have Python bindings for a C++ library that among other things contains classes for describing the static structure of a microprocessor. My background is in Lisp, so I am used to using object identities (references) as keys. The C++ library can be used in this fashion, e.g. looking up a register file by name always returns the same object reference. However, the C++ to Python mapping does not preserve object identity, as a new Python object is created for every query, even if the underlying C++ reference is the same. Is there any easy way to preserve object identity in this sense with Boost Python? My first thought was to use some kind of caching scheme so that consequent queries with a particular name return the same object, but the problem is that objects are not only looked up by name, they can also be returned e.g. by asking for a parent object in a containment hierarchy. -- Pertti