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From: Random832 <random832@fastmail.com>
Newsgroups: comp.lang.python
Subject: Re: Dynamic object attribute creation
Date: Mon, 29 Feb 2016 11:06:04 -0500
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On Mon, Feb 29, 2016, at 10:36, ast wrote:
> but why doesn't it work with built-in classes int, float, list.... ?
> 
> L = [1, 8, 0]
> L.test = 'its a list !'
> 
> (however lists are mutable, int, float ... are not)

Because those classes do not have attribute dictionaries, in order to
save space.

You can make a class without an attribute dictionary, by using
__slots__.