[Python-3000] sets in P3K?

[Alex Martelli]

On 4/24/06, Greg Wilson <gvwilson at cs.utoronto.ca> wrote:
> Interesting --- I think that being able to write down a data structure
> using the same sort of notation you'd use on a whiteboard in a high school
> math class is one of the great strengths of scripting languages, and one
> of the things that makes it possible to use Python, Perl, and Ruby as
> configuration languages (instead of the XML that Java/C# users have to put
> up with).  I think most newcomers will find:
>
> x = {2, 3, 5, 7}
>
> more appealing than:
>
> x = set(2, 3, 5, 7)
>
> though I don't have any data to support that.

It's exactly because we have no data that we can have a cool debate;-).

Python doesn't mean to support set-theory notation -- it doesn't even
have the most elementary operators, such as the epsilon-like thingy
for membership test, the big-funky-U for union and reverse-that for
intersection.  Anybody expecting to use set-theory notation will  be
disappointed nearly instantly, just as soon as they try to DO anything
with their sets, they'll have to use words rather than funky mathlike
glyphs.

So, since you have to code anyway "if z in <someset>" rather than "if
z <epsilonthingy> <someset>", for example, then even for the "funky
mathlike glyphlover" there's little added value if <someset> can be
expressed with funky glyphs rather than spelled out into readable
words. When it comes to operation, we support operator-glyphs such as
& and |, which deviate from set-theoretical notation (and towards
Boolean notation instead) in a way that I suspect might be even more
irking to the set-theory-glyphs lover, and confusing to the high
school student (who might get an F for confusing & with
reverse-U-intersection, if his or her classes cover both settheory and
Boolean logic -- though in the latter case they're more likely to have
to use reverse-V for ``and'', and, once again, Python can't do that).

IOW, it doesn't seem to me that the "high school whiteboard" test can
be even very roughly approximated, so focusing on it for
literals-notation only may do more harm than good; while introducing
"nice readable words with a little punctuation to help out" from the
very start (literals of most types, except numbers and strings) keeps
things and expectations a bit more consistent with each other, as well
as producing code that's easier to read out loud.


Alex