On Tue, Oct 20, 2020 at 11:26 AM Steven D'Aprano <steve@pearwood.info> wrote:
I can't say that I like the look of pseudo-assignment to question mark:

    for ? in range(20):

but I could probably learn to live with it. But one of your

> and makes it more obvious that
> the actual intent is for the value to be unused -- since it is entirely
> impossible to use it.

is actually an anti-feature, in my opinion.

I think that people might like the idea of not actually binding a value
in situations like this:

    a, *?, b = expression

until you end up with something unexpected in a and b and need to debug
what it going on, either in a debugger or with print:

    a, *?, b = expression
    print(?)  # wait this doesn't work;

I'm not sure how this is different than, say,

    a, _, _ = range(3)


    a = range(3)[0]
    print(<whatever the second value is>)

That is to say, some things are impossible; if you want to print the value, don't assign to '?'.

In my opinion, having a convention to treat certain variables as
"unused" is great (I'm partial to `__` myself, to avoid clobbering the
special variable `_` in the REPL). But having that be a pseudo-variable
which is *actually* unused and unuseable strikes me as being an
attractive nuisance.

And yet that's exactly what is being proposed in pattern matching. https://www.python.org/dev/peps/pep-0634/#id3

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