Explanation of list reference

Marko Rauhamaa marko at pacujo.net
Sat Feb 15 14:25:35 CET 2014


Chris Angelico <rosuav at gmail.com>:

> Because everything in Python is an object, and objects always are
> handled by their references. This wouldn't be true in every language
> (eg it's not true of Java's unboxed types), but it's intrinsic to
> Python's object model.

Well, it's part of Python's reference model. Any model that produces
valid Python behavior is equally good. An implementation that boxes some
or all immutable objects would still be perfectly valid.

Anyway, an object is a fairly advanced and abstract concept. A beginning
programmer wouldn't be equipped to understand the ultimate abstraction;
an object is too all-encompassing to express anything. It might be
productive to lead the aspirant to the mountain summit through a more
concrete model. Identifying the references with RAM addresses and
objects with RAM snippets might keep object tangible for the first few
months, although a more mundane model would be welcome.

I'm reminded of Raymond Smullyan's excellent "To Mock the Mockingbird,"
which models combinatory logic with a forest full of chirping birds.


Marko



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