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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Immutability and Python
Date: Mon, 29 Oct 2012 14:03:57 -0400
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Xref: csiph.com comp.lang.python:32412

On 10/29/2012 1:05 PM, andrea crotti wrote:

> I meant how do I create new immutables classes myself, I guess that's
> possible writing C extensions but I don't see in pure Python..

If you mean class with immutable instances, mutate new instances in 
__new__ instead of __init__ and write a custom .__setattr__ that 
prevents changes thereafter.

If you want the class itself to be immutable (after creation), write a 
custom metaclass.

You may also need to think about .__getattribute__, but I never studied 
the detail completely and have forgotten what I learned.

-- 
Terry Jan Reedy