Any possible type alias that can also set a default value for a function arg?

[Chris Angelico]

On Thu, 19 Oct 2023 at 18:25, Karsten Hilbert <Karsten.Hilbert at gmx.net> wrote:
>
> > > > Fundamentally no, at least not without some shenanigans. Type hints do
> > > > not affect the regular running of the code,
> > >
> > > Except when they do ;-)
> > >
> > > ... depending on what counts as (valid) code ...
> > >
> > > In Python a distinction can be made between "runnable" and "valid" :-D
> > >
> >
> > Can you give a counter-example?
>
> As per my recent foray into abusing existence-checking for Singleton assurance
> along such lines as
>
> >>> try: self.initialized
> >>> except AttributeError: print('first instantiation'); self.initialized = True
>
> and then changing that to
>
> >>> try: self.initialized:bool

But that's not equivalent code. You might just as well say that the
ellipsis here suddenly changes the code:

self.initialized
self.initialized = ...

These are completely different, and they behave differently. Both are
valid, but they mean different things.

ChrisA