It's from five days ago. I asked Joshua to take a look at something, but I guess he is busy.
Best, Neil — The latest file there is from Feb 26, while your message that the patch was ready for review is from today -- so is the patch from five days ago the most recent? -- ~Ethan~ On Mon, Mar 2, 2015 at 3:18 PM, Neil Girdhar <mistersh...@gmail.com> wrote: > http://bugs.python.org/issue2292 > > On Mon, Mar 2, 2015 at 3:17 PM, Victor Stinner <victor.stin...@gmail.com> > wrote: > >> Where is the patch? >> >> Victor >> >> Le lundi 2 mars 2015, Neil Girdhar <mistersh...@gmail.com> a écrit : >> >> Hi everyone, >>> >>> The patch is ready for review now, and I should have time this week to >>> make changes and respond to comments. >>> >>> Best, >>> >>> Neil >>> >>> On Wed, Feb 25, 2015 at 2:42 PM, Guido van Rossum <gu...@python.org> >>> wrote: >>> >>>> I'm back, I've re-read the PEP, and I've re-read the long thread with >>>> "(no subject)". >>>> >>>> I think Georg Brandl nailed it: >>>> >>>> """ >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> *I like the "sequence and dict flattening" part of the PEP, mostly >>>> because itis consistent and should be easy to understand, but the >>>> comprehension syntaxenhancements seem to be bad for readability and >>>> "comprehending" what the codedoes.The call syntax part is a mixed bag on >>>> the one hand it is nice to be consistent with the extended possibilities in >>>> literals (flattening), but on the other hand there would be small but >>>> annoying inconsistencies anyways (e.g. the duplicate kwarg case above).* >>>> """ >>>> >>>> Greg Ewing followed up explaining that the inconsistency between dict >>>> flattening and call syntax is inherent in the pre-existing different rules >>>> for dicts vs. keyword args: {'a':1, 'a':2} results in {'a':2}, while f(a=1, >>>> a=2) is an error. (This form is a SyntaxError; the dynamic case f(a=1, >>>> **{'a': 1}) is a TypeError.) >>>> >>>> For me, allowing f(*a, *b) and f(**d, **e) and all the other >>>> combinations for function calls proposed by the PEP is an easy +1 -- it's a >>>> straightforward extension of the existing pattern, and anybody who knows >>>> what f(x, *a) does will understand f(x, *a, y, *b). Guessing what f(**d, >>>> **e) means shouldn't be hard either. Understanding the edge case for >>>> duplicate keys with f(**d, **e) is a little harder, but the error messages >>>> are pretty clear, and it is not a new edge case. >>>> >>>> The sequence and dict flattening syntax proposals are also clean and >>>> logical -- we already have *-unpacking on the receiving side, so allowing >>>> *x in tuple expressions reads pretty naturally (and the similarity with *a >>>> in argument lists certainly helps). From here, having [a, *x, b, *y] is >>>> also natural, and then the extension to other displays is natural: {a, *x, >>>> b, *y} and {a:1, **d, b:2, **e}. This, too, gets a +1 from me. >>>> >>>> So that leaves comprehensions. IIRC, during the development of the >>>> patch we realized that f(*x for x in xs) is sufficiently ambiguous that we >>>> decided to disallow it -- note that f(x for x in xs) is already somewhat of >>>> a special case because an argument can only be a "bare" generator >>>> expression if it is the only argument. The same reasoning doesn't apply (in >>>> that form) to list, set and dict comprehensions -- while f(x for x in xs) >>>> is identical in meaning to f((x for x in xs)), [x for x in xs] is NOT the >>>> same as [(x for x in xs)] (that's a list of one element, and the element is >>>> a generator expression). >>>> >>>> The basic premise of this part of the proposal is that if you have a >>>> few iterables, the new proposal (without comprehensions) lets you create a >>>> list or generator expression that iterates over all of them, essentially >>>> flattening them: >>>> >>>> >>> xs = [1, 2, 3] >>>> >>> ys = ['abc', 'def'] >>>> >>> zs = [99] >>>> >>> [*xs, *ys, *zs] >>>> [1, 2, 3, 'abc', 'def', 99] >>>> >>> >>>> >>>> But now suppose you have a list of iterables: >>>> >>>> >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>>> >>> [*xss[0], *xss[1], *xss[2]] >>>> [1, 2, 3, 'abc', 'def', 99] >>>> >>> >>>> >>>> Wouldn't it be nice if you could write the latter using a comprehension? >>>> >>>> >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>>> >>> [*xs for xs in xss] >>>> [1, 2, 3, 'abc', 'def', 99] >>>> >>> >>>> >>>> This is somewhat seductive, and the following is even nicer: the *xs >>>> position may be an expression, e.g.: >>>> >>>> >>> xss = [[1, 2, 3], ['abc', 'def'], [99]] >>>> >>> [*xs[:2] for xs in xss] >>>> [1, 2, 'abc', 'def', 99] >>>> >>> >>>> >>>> On the other hand, I had to explore the possibilities here by >>>> experimenting in the interpreter, and I discovered some odd edge cases >>>> (e.g. you can parenthesize the starred expression, but that seems a >>>> syntactic accident). >>>> >>>> All in all I am personally +0 on the comprehension part of the PEP, and >>>> I like that it provides a way to "flatten" a sequence of sequences, but I >>>> think very few people in the thread have supported this part. Therefore I >>>> would like to ask Neil to update the PEP and the patch to take out the >>>> comprehension part, so that the two "easy wins" can make it into Python 3.5 >>>> (basically, I am accepting two-thirds of the PEP :-). There is some time >>>> yet until alpha 2. >>>> >>>> I would also like code reviewers (Benjamin?) to start reviewing the >>>> patch <http://bugs.python.org/issue2292>, taking into account that the >>>> comprehension part needs to be removed. >>>> >>>> -- >>>> --Guido van Rossum (python.org/~guido) >>>> >>>> >>> >
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