On Fri, 6 Dec 2019 at 09:33, Steven D'Aprano <[email protected]> wrote:
>
> Although I am cautiously and tentatively in favour of setting limits
> if the benefits Mark suggests are correct, I have thought of at least
> one case where a million classes may not be enough.
>
> I've seen people write code like this:
>
> for attributes in list_of_attributes:
> obj = namedtuple("Spam", "fe fi fo fum")(*attributes)
> values.append(obj)
>
>
> not realising that every obj is a singleton instance of a unique class.
> They might end up with a million dynamically created classes, each with
> a single instance, when what they wanted was a single class with a
> million instances.
But isn't that the point here? A limit would catch this and prompt
them to rewrite the code as
cls = namedtuple("Spam", "fe fi fo fum")
for attributes in list_of_attributes:
obj = cls(*attributes)
values.append(obj)
> Could there be people doing this deliberately? If so, it must be nice
> to have so much RAM that we can afford to waste it so prodigiously: a
> namedtuple with ten items uses 64 bytes, but the associated class uses
> 444 bytes, plus the sizes of the methods etc. But I suppose there could
> be a justification for such a design.
You're saying that someone might have a justification for deliberately
creating a million classes, based on an example that on the face of it
is a programmer error (creating multiple classes when a single shared
class would be better) and presuming that there *might* be a reason
why this isn't an error? Well, yes - but I could just as easily say
that someone might have a justification for creating a million classes
in one program, and leave it at that. Without knowing (roughly) what
the justification is, there's little we can take from this example.
Having said that, I don't really have an opinion on this change.
Basically, I feel that it's fine, as long as it doesn't break any of
my code (which I can't imagine it would) but that's not very helpful!
https://xkcd.com/1172/ ("Every change breaks someone's workflow")
comes to mind here.
Paul
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