On Mon, May 31, 2021 at 11:41 PM Steven D'Aprano <st...@pearwood.info>
wrote:
> It's pretty standard behaviour for Python. Right now, `eval(repr(...))`
> works unless you have shadowed the name
> Ellipsis.
>
> >>> err = ValueError('something went wrong')
> >>> ValueError = list
> >>> eval(repr(err))
> ['s', 'o', 'm', 'e', 't', 'h', 'i', 'n', 'g', ' ', 'w', 'e', 'n',
> 't', ' ', 'w', 'r', 'o', 'n', 'g']
>
Yeah, my surprise was kind of a "thinko." I think I was thinking of the
eval() separately from the repr(). But nonetheless, the idempotency
question still arises, and I believe is reasonable.
> Unless we make the ellipsis object `...` callable. But that doesn't help
> us if the name Ellipsis has been rebound. Then it will call the rebound
> object.
>
> Let's change the behavior of the Ellipsis object slightly to have either a
> .__call__() or .__getitem__() method that returns itself
That was exactly what I suggested. The three dots themselves, which CANNOT
be bound to any other object, could be callable or indexable. If you
define a class Ellipsis to use that name, it makes no difference to
`repr(...) == "...[Ellipsis]"` Note that I am NOT proposing
`Ellipsis(...)` as the repr for EXACTLY that reason.
> Not every builtin needs a mollyguard to protect against misuse.
>
I'm not likely to rebind `Ellipsis` so that's not really my concern.
Rather, I'm interested in the point André Roberge started the thread with.
The repr of '...' should be more self-explanatory to beginners. It's
basically co-opting the square brackets or parenthesis to mean something
that doesn't really have anything to do with calling or indexing in order
to have a repr—in tracebacks specifically, but elsewhere also—that reminds
users of the connection between `...` and `Ellipsis`.
--
The dead increasingly dominate and strangle both the living and the
not-yet born. Vampiric capital and undead corporate persons abuse
the lives and control the thoughts of homo faber. Ideas, once born,
become abortifacients against new conceptions.
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