Nice!
On Sun, Oct 25, 2020 at 9:59 PM Dennis Sweeney <sweeney.dennis...@gmail.com>
wrote:
> What if the mapping assignment were more harmonious with the pattern
> matching PEP? Something like this:
>
> items = {'eggs': 2, 'cheese': 3, 'spam': 1}
> {'eggs': eggs, 'spam': i_dont_need_to_name_this_spam, **rest} = items
> assert i_dont_need_to_name_this_spam == 1
> assert eggs == 2 and cheese == 3
> assert rest == {'cheese': 3}
>
> The keys here could be arbitrary hashables and the "values" could be
> arbitrary assignment targets (assigned all-or-nothing). This wouldn't need
> the right-hand-side double-star, and I think it more closely resembles the
> sequence unpacking assignment syntax. You can assign to a (thing that looks
> like a) tuple or to a (thing that looks like a) list or to a sequence
> subscript or object attribute, why not be able to assign to a (thing that
> looks like a) dictionary? This also avoids polluting the local namespace in
> case one of your keys is the string "range" or something. It also feels
> less magical to me, albeit more verbose.
>
> Calls to a hypothetical parse/sscanf function could closely mirror some
> str.format() calls:
>
> text = "{a}, {b}, {c}".format(**{'a': a0, 'b': b0, 'c': c0})
> {'a': a1, 'b': b1, 'c': c1} = "{a}, {b}, {c}".parse(text)
> assert (a1, b1, c1) == (a0, b0, c0)
>
> Alternative positional parsing would be useful as well, as in:
>
> text = "{}, {}, {}".format(a0, b0, c0)
> a1, b1, c1 = "{}, {}, {}".parse(text)
> assert (a1, b1, c1) == (a0, b0, c0)
>
> This way, pattern.format() and pattern.parse() would be trying to be
> inverses of each other (as much as is reasonable, probably limited to
> parsing strings, floats and ints).
>
> Then maybe people could get used to a format-string-like mini-language for
> parsing, and eventually, the f-string assignment might be better received,
> and we could propose something like
>
> text = f"{a0}, {b0}, {c0}"
> f"{a1}, {b1}, {c1}" = text
> assert (a1, b1, c1) == (a0, b0, c0)
>
> as well, where we lose some of the flexibility but gain better D.R.Y. and
> more visual locality, useful in the simple cases. I see the potential for a
> strong analogy:
>
> positional format() : keyword-based format() : fstrings
> ::
> positional parse() : keyword-based parse(): assignment to fstrings
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--
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*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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