On Sep 2, 2019, at 23:50, Philippe Prados <[email protected]> wrote:
>
> Like Kotlin, add a new `?` operator to use syntax like `int?` ou `?int` ?
> CONS: It’s not compatible with IPython and Jupyter Lab `?smth` displays help
> for symbol `smth`
> CONS: With default arguments, `?=` looks... not great
> def f(source: str?=def_src, destination: str?=MISSING, param: int?=1): ...
This has a lot more precedents than Kotlin; it’s a widespread spelling across a
variety of modern languages.
The incompatibility with IPython isn’t that big a deal in practice, for the
reasons I explained when I raised the issue in the first place.
Using a `?` suffix isn’t just potentially ugly as in your example, it’s also
potentially confusing given languages that use `?=` as null-coalescing
assignment or equality, not to mention forever closing off the possibility of
adding that feature to Python (which was rejected both times I remember it
coming up, but people do still occasionally propose it anew).
But I don’t think `?` as a prefix has either the ugliness problem or the
cross-language confusion problem:
def func(source: ?str=def_src, destination: ?str=MISSING):
(I mean, it’s still not beautiful, but that’s just the usual brevity vs.
familiarity issue, not a matter of having to parse in your head which part of
the expression the `?` belongs to.)
Also, `?` is a new operator. And it uses up one of the few ASCII symbols that
Python hasn’t yet given a meaning to. Which doesn’t rule it out (unless we want
to be like Go and explicitly permanently reserve `?` to mean “some unknown
future feature that’s so amazing that it’s better than whatever feature you
think you want to use it for”), but it does make the hurdle a lot higher than
using `~`.
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