Re: Re: Re: Re: Any possible type alias that can also set a default value for a function arg?
On Thu, 19 Oct 2023 at 19:34, Karsten Hilbert wrote:
>
> > > 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.
>
> I learned as much (RHS vs LHS).
>
> But it did not _intuitively_ resonate with the sentiment
> "type annotation does not change the running of code".
Unfortunately, that simply means that your intuition was wrong. It
doesn't change my prior statement.
ChrisA
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Aw: Re: Re: Re: Any possible type alias that can also set a default value for a function arg?
> > 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.
I learned as much (RHS vs LHS).
But it did not _intuitively_ resonate with the sentiment
"type annotation does not change the running of code".
Karsten
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Re: Re: Re: Any possible type alias that can also set a default value for a function arg?
On Thu, 19 Oct 2023 at 18:25, Karsten Hilbert 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
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