Explanation of list reference

[Ian Kelly]

On Fri, Feb 14, 2014 at 9:24 PM, Rustom Mody <rustompmody at gmail.com> wrote:
> In the case of physical objects like dice there is a fairly
> unquestionable framing that makes identity straightforward --
> 4-dimensional space-time coordiantes. If the space-time coordinates of
> 2 objects are all equal then the objects are identical, else not.
>
> Now we analogize the space-time identity of physical objects to
> computer identity of computer objects (so-called) and all sorts of
> problems ensue.
>
> To start with we say two objects are identical if they have the same
> memory address.

This is false.  It happens to hold for CPython, but that's an
implementation detail.  The definition of object identity does not
depend on memory address.  It also doesn't have anything to do with
space-time coordinates.  The concept of object identity is an
abstraction, not an analogy from physics.

The language reference states, "Every object has an identity, a type
and a value. An object's identity never changes once it has been
created; you may think of it as the object's address in memory."
Okay, so that quote does bring up memory address, but in my
interpretation that's just an analogy to introduce the concept.  The
more important part of that sentence is the first part, which ties an
object's identity to its creation.  If two objects share the same
creation, then they're the same object.