[Python-Dev] Replacing self.__dict__ in __init__

[Tin Tvrtković]

Thank you to everyone who participated (Kirill, Raymond, Nick, Naoki). I've
decided there are too many caveats for this approach to be worthwhile and
I'm giving up on it.

Kind regards,
Tin

On Sat, Mar 24, 2018 at 3:18 PM Tin Tvrtković <tinchester at gmail.com> wrote:

> Hi Python-dev,
>
> I'm one of the core attrs contributors, and I'm contemplating applying an
> optimization to our generated __init__s. Before someone warns me python-dev
> is for the development of the language itself, there are two reasons I'm
> posting this here:
>
> 1) it's a very low level question that I'd really like the input of the
> core devs on, and
> 2) maybe this will find its way into dataclasses if it works out.
>
> I've found that, if a class has more than one attribute, instead of
> creating an init like this:
>
>     self.a = a
>     self.b = b
>     self.c = c
>
> it's faster to do this:
>
>     self.__dict__ = {'a': a, 'b': b, 'c': c}
>
> i.e. to replace the instance dictionary altogether. On PyPy, their core
> devs inform me this is a bad idea because the instance dictionary is
> special there, so we won't be doing this on PyPy.
>
> But is it safe to do on CPython?
>
> To make the question simpler, disregard the possibility of custom setters
> on the attributes.
>
> Thanks in advance!
>
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