On Thu, 22 Apr 2021 at 15:22, Adrian Freund <m...@freundtech.com> wrote:
>
> On April 22, 2021 3:15:27 PM GMT+02:00, Paul Moore <p.f.mo...@gmail.com>
> wrote:
> >but that's *absolutely* as far as I'd want to go. Note in particular
> >that I don't want to constrain the return value
> The problem is that this isn't enough to have a type safe program. You need
> to also constrain the return type to make sure the returned value can be
> safely passed to other functions.
But I don't want a type safe program. At least not in an absolute
sense. All I want is for mypy to catch the occasional error I make
where I pass the wrong parameter. For me, that's the "gradual" in
"gradual typing" - it's not a lifestyle, just a convenience. You seem
to be implying that it's "all or nothing".
> If you don't do this large parts of your codebase will either need explicit
> annotations or will be unchecked.
That's just not true. (And even if it were true, you're assuming that
I care - I've already said that my goal is much more relaxed than
complete type safety).
I repeat, all I'm proposing is that
def f(x: int): ...
def g(x: str): ...
def main(t: DuckTyped) -> None:
if t[0] == 'version':
f(t[1])
elif t[0] == 'name':
g(t[1])
gets interpreted *exactly* the same as if I'd written
class TType(Protocol):
def __getitem__(self, int): ...
def f(x: int): ...
def g(x: str): ...
def main(t: TType) -> None:
if t[0] == 'version':
f(t[1])
elif t[0] == 'name':
g(t[1])
How can you claim that the second example requires that " large parts
of your codebase will either need explicit annotations or will be
unchecked"? And if the second example doesn't require that, nor does
the first because it's equivalent.
Honestly, this conversation is just reinforcing my suspicion that
people invested in type annotations have a blind spot when it comes to
dealing with people and use cases that don't need to go "all in" with
typing :-(
Paul
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