On Fri, Sep 18, 2020, 9:16 AM Chris Angelico <ros...@gmail.com> wrote:
> On Fri, Sep 18, 2020 at 11:04 PM Ricky Teachey <ri...@teachey.org> wrote:
> >
> > On Fri, Sep 18, 2020, 8:34 AM Chris Angelico <ros...@gmail.com> wrote:
> >>
> >> On Fri, Sep 18, 2020 at 10:26 PM Ricky Teachey <ri...@teachey.org>
> wrote:
> >> >
> >> > On Fri, Sep 18, 2020, 8:17 AM Ricky Teachey <ri...@teachey.org>
> wrote:
> >> >>
> >> >>
> >> >> Why not just grow a parse method on str that returns a dict and do
> it this way?
> >> >>
> >> >>
> >> >> q = "{a} {b}"
> >> >> p = "1 2"
> >> >> (a, b) = q.parse(p)
> >> >
> >> >
> >> > Sorry that should have been:
> >> >
> >> > (a, b) = q.parse(p).values()
> >> >
> >>
> >> You're using a dictionary as if it were a tuple. That's going to cause
> >> a LOT of pain when someone does something like:
> >>
> >> a, b = "{b} {a}".parse(p).values()
> >>
> >> and they come out in the wrong order. Bad bad bad idea. Don't have
> >> names if they're going to be pure lies.
> >>
> >> ChrisA
> >
> >
> > I'm not sure I understand the point you are making here since
> dictionaries have preserved order since python 3.6...?
> >
> > The same problem exists here:
> >
> > a, b = 2, 1
> > assert a == 1. # whoops got the order wrong
> >
>
> But you don't have any sort of lie in the RHS about the name mapping.
> It's just a sequence, so people will expect it to be a sequence. If
> the parser incorporates names, people will expect it to use those
> names. Why have it return a dictionary if you're going to assume and
> mandate that it be a sequence?
>
> ChrisA
>
I see your point now. Missed it before: the lie inherent to using the names
not the order.
But that seems to me to be an argument for dictionaries, not against. You
can at least consult the dictionary to find out what name was used to grab
the value.
And again, similar things can happen in other contexts and it's just
people's responsibility to get it right.
d = dict(b=1, a=2)
a1, b1, a2, b2 = {**d, **d}.values()
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/P4CRHIBTNMPV6ZLVI2AFIFAVIND7YBIN/
Code of Conduct: http://python.org/psf/codeofconduct/
