What variable type is returned from Open()?

[Souvik Dutta]

Then there is no point of type setting. Type setting is a personal
preferences and should be respected. Sometimes it saves the day. Sometimes
it becomes a headache. Python developers also know and thus have never
deprecated type setting.

On Fri, 17 Apr, 2020, 12:40 am Chris Angelico, <rosuav at gmail.com> wrote:

> On Fri, Apr 17, 2020 at 5:06 AM <dcwhatthe at gmail.com> wrote:
> >
> > On Thursday, April 16, 2020 at 2:37:42 PM UTC-4, Chris Angelico wrote:
> > > On Fri, Apr 17, 2020 at 2:13 AM Richard Damon <Richard> wrote:
> > > > I get the answer: <class '_io.TextIOWrapper'>
> > > >
> > > > So that is the name of the type that is returned, at least for that
> > > > call. One key thing to note is that it begins with a _, so that type
> is
> > > > actually an implementation detail, subject to change.
> > >
> > > This is somewhat true; but when the *module* begins with an
> > > underscore, it often means it's a C accelerator for a Python module.
> > > You can often find the same thing exposed in a more visible way:
> > >
> > > >>> import io
> > > >>> io.TextIOWrapper
> > > <class '_io.TextIOWrapper'>
> > >
> > > And in that location, it is fully documented:
> > >
> > > https://docs.python.org/3/library/io.html#io.TextIOWrapper
> > >
> > > The fact that it comes from the accelerator *is* an internal
> > > implementation detail, but the class itself is a public one.
> > >
> > > That said, though: it is still very much incorrect to type hint in
> > > this way. The correct type hint is a generic one:
> > >
> > > https://docs.python.org/3/library/typing.html#typing.IO
> > >
> > > And the correct way to encode this on a variable is to let type
> > > inference figure it out. You'd use typing.IO or typing.TextIO to
> > > annotate a function parameter, perhaps, but don't annotate your
> > > variables at all.
> > >
> > > ChrisA
> >
> > "And the correct way to encode this on a variable is to let type
> > inference figure it out. You'd use typing.IO or typing.TextIO to
> > annotate a function parameter, perhaps, but don't annotate your
> > variables at all."
> >
> > I don't know how many times I have to say this, but I've already decided
> that the types of variables are going to be part of my code base.  Same as
> every other language I've programmed in, whether statically or dynamically
> typed.
> >
> > I don't care if it's 'incorrect' for most purposes.  I'm doing it, for
> my specific purpose.
> >
>
> Oh! Okay then. Just annotate it as "int" - it's no more or less wrong
> than any other annotation :) Problem solved!
>
> ChrisA
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