On 2019年01月18日 00:48, Gregory P. Smith wrote:
I've heard that libraries using ctypes, cffi, or cython code of
various
sorts in the real world wild today does abuse the unfortunate side
effect of CPython's implementation of id(). I don't have specific
instances of this in mind but trust what I've heard: that it is
happening.
id() should never be considered to be the PyObject*. In as much as
code
shouldn't assume it is running on top of a specific CPython
implementation.
If there is a _need_ to get a pointer to a C struct handle
referencing a
CPython C API PyObject, we should make an explicit API for that
rather
than the id() hack. That way code can be explicit about its need,
and
code that is just doing a funky form of identity tracking without
using
is and is not can continue using id() without triggering regressive
behavior on VMs that don't have a CPython compatible PyObject under
the
hood by default.
[who uses id() anyways?]
I use it in some of my code.
If I want to cache some objects, I put them in a dict, using the id
as
the key. If I wanted to locate an object in a cache and didn't have
id(), I'd have to do a linear search for it.