Movatterモバイル変換

[Python-Dev] Tricky way of of creating a generator via a comprehension expression

• Previous message (by thread):[Python-Dev] Tricky way of of creating a generator via a comprehension expression
• Next message (by thread):[Python-Dev] Tricky way of of creating a generator via a comprehension expression
• Messages sorted by:[ date ][ thread ][ subject ][ author ]

On 22 November 2017 at 17:16, Paul Moore <p.f.moore at gmail.com> wrote:> On 22 November 2017 at 16:08, Ivan Levkivskyi <levkivskyi at gmail.com>> wrote:> > On 22 November 2017 at 16:56, Yury Selivanov <yselivanov.ml at gmail.com>> > wrote:> >>> >> On Wed, Nov 22, 2017 at 10:10 AM, Ivan Levkivskyi <levkivskyi at gmail.com> >> >> wrote:> >> > On 22 November 2017 at 15:47, Paul Moore <p.f.moore at gmail.com> wrote:> >> [...]> >> I'm all for prohibiting using 'yield' expression in generator> >> expressions or comprehensions.  The semantics is way to hard to> >> understand and hence be of any value.> >>> >> Making 'await' a SyntaxError is absolutely not an option.  Async> >> generator expressions are a shorthand syntax for defining asynchronous> >> generators (PEP 525), and it's already being used in the wild.> >> >> > OK, makes sense, so it looks like we may have the following plan:> >> > - fix `yield` in comprehensions>> I'm still not clear what "fix" would actually mean, but you propose> clarifying the docs below, so I assume it means "according to whatever> the updated docs say"...>>I mean the initial proposal: make comprehensions equivalent to a for-loop> > - update PEP 530 and docs re generator expressions vs comprehensions>> Docs more importantly than PEP IMO. And are you implying that there's> a difference between generator expressions and comprehensions? I> thought both were intended to behave as if expanded to a function> containing nested for loops? Nothing said in this thread so far (about> semantics, as opposed to about current behaviour) implies there's a> deliberate difference.>I think there may be a difference:comprehension `g = [(yield i) for i in range(3)]` is defined as this code:    __result = []    __i = None    try:        for __i in range(3):            __result.append(yield __i)        g = __result    finally:        del __result, __iwhile `g = list((yield i) for i in range(3))` is defined as this code:    def __gen():       for i in range(3):         yield (yield i)    g = list(__gen()) Although these two definitions are equivalent in simple cases (like having`f(i)` instead of `yield i`)But this is debatable, I think before we move to other points we need toagree on the clear definitions of semantics of generator expressions andcomprehensions.--Ivan-------------- next part --------------An HTML attachment was scrubbed...URL: <http://mail.python.org/pipermail/python-dev/attachments/20171122/8b2e865a/attachment.html>

• Previous message (by thread):[Python-Dev] Tricky way of of creating a generator via a comprehension expression
• Next message (by thread):[Python-Dev] Tricky way of of creating a generator via a comprehension expression
• Messages sorted by:[ date ][ thread ][ subject ][ author ]