+1 from me, I've actually had several situations where I was in need of such notation.
I also think that the proposed syntax in intuitive enough so that it should not cause any confusion.

On Wed, Oct 20, 2021 at 2:08 AM Steven D'Aprano <steve@pearwood.info> wrote:
On Sun, Oct 17, 2021 at 05:02:23PM -0700, Guido van Rossum wrote:
> On Sun, Oct 17, 2021 at 4:38 PM Steven D'Aprano <steve@pearwood.info> wrote:
> > Right-o, the old "heterogeneous tuples versus homogeneous lists"
> > distinction, I remember that from the old 1.5 days. I haven't heard it
> > mentioned for a long time!
> >
> You must not have looked at type annotations then. :-)

Not closely enough to draw the connection unprompted, no. Thanks for the

> Type annotations
> legitimize this, by favoring the syntax list[int] for a homogeneous list
> versus tuple[int, str, bool] for a heterogeneous tuple. (There's a syntax
> for a homogeneous tuple too, but it's intentionally slightly longer.)

This makes sense.

> So this rule of thumb is definitely not dead (as you seemed to imply).

What I actually said:

"That certainly remains a reasonable guideline to make, albeit less so

(and then gave reasons why less so).

I explicitly agreed that it still is a good distinction to make. It is a
particularly egregiously unfair misrepresentation to say I "seemed to
imply" otherwise. That's not cool.

Another factor in favour of the heterogeneous vs homogeneous distinction
is the practical difficulty in working with complex data structures made
from tuples, due to their immutability. I've just spent some time using
an API that represents data as nested tuples, and due to their
immutability they can be a pain to assemble. Nested lists are much

It's okay if you know your data up front and can write it as a nested
tuple display, but if you need to assemble it dynamically, it is not
fun. Would not recommend.

Fortunately it's my own API and so I can take a flame thrower to it and
replace it with something better :-)

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