[C++-sig] Boost Python objects and object identity

[Roman Yakovenko]

2009/9/29 Pertti Kellomäki <pertti.kellomaki at tut.fi>:
> 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.

A while ago I introduce to Py++ some kind of functionality, which
integrates with CTYPES package.

For example, you can expose "this" pointer to Python and use it as your id:

http://language-binding.net/pyplusplus/documentation/ctypes/this_and_sizeof.html

HTH

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/