Re: [Python-ideas] Generator syntax hooks?

Though I still dop'nt think using "while" would really introduce that much confusion -- sure, it doesn't introduce a new loop, but, as someone pointed out earlier in this thread it really is only changing from a: "while do" to a "do while" construct -- so means pretty much the same thing. +1

Re: [Python-ideas] Generator syntax hooks?

[...] > result = [] > for x in sequence: > if condition: > result.append(expression) > else: > break > > which could be written > > [expression for x in sequence if condition break] > > It's what I thought too. Adding a `while` clause here just overly > complicates the

Re: [Python-ideas] Generator syntax hooks?

On 11 August 2017 at 05:49, Steven D'Aprano wrote: > On Thu, Aug 10, 2017 at 01:25:24PM -0700, Chris Barker wrote: >> On Thu, Aug 10, 2017 at 8:39 AM, Paul Moore wrote: >> >> >> > Also, there's a potential issue >> > here - consider >> > >> > [expr

Re: [Python-ideas] Generator syntax hooks?

On 11 August 2017 at 15:13, Steven D'Aprano wrote: > On Fri, Aug 11, 2017 at 02:34:53PM +1000, Nick Coghlan wrote: >> This is another good reason why a termination condition would need to >> be checked before the filter condition rather than either after it, or >> only when

Re: [Python-ideas] Generator syntax hooks?

On Fri, Aug 11, 2017 at 02:49:10PM +1000, Steven D'Aprano wrote: > On Thu, Aug 10, 2017 at 01:25:24PM -0700, Chris Barker wrote: > > I guess I think of it like this: > > > > "if" is providing a filtering mechanism > > > > "while" is providing a termination mechanism > > > > -- is there a use

Re: [Python-ideas] Generator syntax hooks?

On Fri, Aug 11, 2017 at 02:34:53PM +1000, Nick Coghlan wrote: > This is actually how I came to the conclusion that if we were ever to > do something like this, the termination condition would need to go > *before* the filter condition: What if you want to check the filter condition before the

Re: [Python-ideas] Generator syntax hooks?

On 11 August 2017 at 06:53, Spencer Brown wrote: > The logical solution to me is to allow any order of while and if, and follow > the same 'rule' as multiple for loops - just nest/test those in that order. > Then you can have whatever priority you need. One question though is

Re: [Python-ideas] Generator syntax hooks?

On Thu, Aug 10, 2017 at 01:25:24PM -0700, Chris Barker wrote: > On Thu, Aug 10, 2017 at 8:39 AM, Paul Moore wrote: > > > > Also, there's a potential issue > > here - consider > > > > [expr for var in even_numbers() if is_odd(var) while var < 100] > > > > This is an

Re: [Python-ideas] Generator syntax hooks?

On 11 August 2017 at 01:39, Paul Moore wrote: > On 10 August 2017 at 14:42, Steven D'Aprano wrote: >> I don't think it is confusing. Regardless of the implementation, the >> meaning of: >> >> [expression for x in sequence while condition] >> >> should (I

Re: [Python-ideas] Generator syntax hooks?

On Thu, Aug 10, 2017 at 1:53 PM, Spencer Brown wrote: > The logical solution to me is to allow any order of while and if, and > follow the same 'rule' as multiple for loops - just nest/test those in that > order. > Actually, I think it would be better to only allow one

Re: [Python-ideas] Generator syntax hooks?

The logical solution to me is to allow any order of while and if, and follow the same 'rule' as multiple for loops - just nest/test those in that order. Then you can have whatever priority you need. One question though is how this should handle multiple loops - break all of them, or just the

Re: [Python-ideas] Generator syntax hooks?

On 10 August 2017 at 21:25, Chris Barker wrote: > On Thu, Aug 10, 2017 at 8:39 AM, Paul Moore wrote: > >> >> Also, there's a potential issue >> here - consider >> >> [expr for var in even_numbers() if is_odd(var) while var < 100] >> >> This is an

Re: [Python-ideas] Generator syntax hooks?

On Thu, Aug 10, 2017 at 1:03 PM, Terry Reedy wrote: > After all, we have "break" in both for and while loops, so clearly there is >>> the use case... >>> >> > In both cases, we use 'break' to mean break. If we want to break > comprehensions, I think we should continue to use

Re: [Python-ideas] Generator syntax hooks?

On Thu, Aug 10, 2017 at 8:39 AM, Paul Moore wrote: > Also, there's a potential issue > here - consider > > [expr for var in even_numbers() if is_odd(var) while var < 100] > > This is an infinite loop, even though it has a finite termination > condition (var < 100),

Re: [Python-ideas] Generator syntax hooks?

On 8/10/2017 9:42 AM, Steven D'Aprano wrote: On Wed, Aug 09, 2017 at 01:23:28PM -0700, Chris Barker wrote: I can't recall the use case(s) at the moment, but I have definitely wanted a way to break out of a comprehension -- and not always with infinite iterators. After all, we have "break" in

Re: [Python-ideas] Generator syntax hooks?

On 2017-08-10 01:11 PM, Steven D'Aprano wrote: On Thu, Aug 10, 2017 at 12:39:34PM -0300, Soni L. wrote: I'm pretty sure I read somewhere that lambdas and generators share their syntax, and that syntax is already a subset of python syntax. Would it be too hard to expose that with a

Re: [Python-ideas] Generator syntax hooks?

On 2017-08-10 01:43 AM, Nick Coghlan wrote: On 10 August 2017 at 01:49, Soni L. wrote: On 2017-08-09 11:54 AM, Nick Coghlan wrote: Right, I was separating the original request to make "{x for x in integers if 1000 <= x < 100}" work into the concrete proposal to

Re: [Python-ideas] Generator syntax hooks?

On 10 August 2017 at 14:42, Steven D'Aprano wrote: > I don't think it is confusing. Regardless of the implementation, the > meaning of: > > [expression for x in sequence while condition] > > should (I believe) be obvious to anyone who already groks comprehension > syntax. The

Re: [Python-ideas] Generator syntax hooks?

On Thu, Aug 10, 2017 at 12:54:57AM +1000, Nick Coghlan wrote: Guido wrote: > > I haven't come around to this yet. It looks like it will make explaining > > comprehensions more complex, since the translation of "while X" into "if not > > X: break" feels less direct than the translations of "for x

Re: [Python-ideas] Generator syntax hooks?

On Wed, Aug 09, 2017 at 01:23:28PM -0700, Chris Barker wrote: > I can't recall the use case(s) at the moment, but I have definitely wanted > a way to break out of a comprehension -- and not always with infinite > iterators. > > After all, we have "break" in both for and while loops, so clearly

Re: [Python-ideas] Generator syntax hooks?

On 10 August 2017 at 01:49, Soni L. wrote: > On 2017-08-09 11:54 AM, Nick Coghlan wrote: >> Right, I was separating the original request to make "{x for x in >> integers if 1000 <= x < 100}" work into the concrete proposal to >> make exactly *that* syntax work (which I

Re: [Python-ideas] Generator syntax hooks?

On 10 August 2017 at 00:54, Nick Coghlan wrote: > Yeah, if we ever did add something like this, I suspect a translation > using takewhile would potentially be easier for at least some users to > understand than the one to a break condition: > > {x for x in

Re: [Python-ideas] Generator syntax hooks?

On 8/9/2017 10:54 AM, Nick Coghlan wrote: On 9 August 2017 at 15:38, Guido van Rossum wrote: On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan wrote: The OP's proposal doesn't fit into that category though: rather it's asking about the case where we have an

Re: [Python-ideas] Generator syntax hooks?

On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan wrote: > On 8 August 2017 at 09:06, Chris Barker wrote: > > It would be nice to have an easier access to an "slice iterator" though > -- > > one of these days I may write up a proposal for that. > > An idea

Re: [Python-ideas] Generator syntax hooks?

On 2017-08-09 11:54 AM, Nick Coghlan wrote: On 9 August 2017 at 15:38, Guido van Rossum wrote: On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan wrote: The OP's proposal doesn't fit into that category though: rather it's asking about the case where we have

Re: [Python-ideas] Generator syntax hooks?

On 9 August 2017 at 15:38, Guido van Rossum wrote: > On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan wrote: >> The OP's proposal doesn't fit into that category though: rather it's >> asking about the case where we have an infinite iterator (e.g. >>

Re: [Python-ideas] Generator syntax hooks?

Nick Coghlan writes: > Right now, getting the "terminate when false" behaviour requires the > use of takewhile: > > {itertools.takewhile(lambda x: x < 100, itertools.count(1000)} My objection to this interpretation is different from Guido's (I think): if you're really thinking in

Re: [Python-ideas] Generator syntax hooks?

On Tue, Aug 8, 2017 at 10:06 PM, Nick Coghlan wrote: > On 8 August 2017 at 09:06, Chris Barker wrote: > > It would be nice to have an easier access to an "slice iterator" though > -- > > one of these days I may write up a proposal for that. > > An idea

Re: [Python-ideas] Generator syntax hooks?

On 8 August 2017 at 09:06, Chris Barker wrote: > It would be nice to have an easier access to an "slice iterator" though -- > one of these days I may write up a proposal for that. An idea I've occasionally toyed with [1] is some kind of "iterview" that wraps around an

Re: [Python-ideas] Generator syntax hooks?

> Soni L. writes: > Steven d'Aprano writes: > > range(1000, 100) > > (x for x in range(1000, 100)) # waste of time and effort > Actually, those have different semantics! That's not real important. As Stefan Behnel points out, it's simple (and efficient) to get iterator

Re: [Python-ideas] Generator syntax hooks?

Soni L. schrieb am 08.08.2017 um 01:56: > On 2017-08-07 08:35 PM, Steven D'Aprano wrote: >> Hi Soni, and welcome! >> >> On Mon, Aug 07, 2017 at 04:30:05PM -0300, Soni L. wrote: >> >>> What if, (x for x in integers if 1000 <= x < 100), was syntax sugar >>> for (x for x in range(1000, 100))?

Re: [Python-ideas] Generator syntax hooks?

On 2017-08-07 08:35 PM, Steven D'Aprano wrote: Hi Soni, and welcome! On Mon, Aug 07, 2017 at 04:30:05PM -0300, Soni L. wrote: What if, (x for x in integers if 1000 <= x < 100), was syntax sugar for (x for x in range(1000, 100))? If you want the integers from 1000 to 100, use:

Re: [Python-ideas] Generator syntax hooks?

Hi Soni, and welcome! On Mon, Aug 07, 2017 at 04:30:05PM -0300, Soni L. wrote: > What if, (x for x in integers if 1000 <= x < 100), was syntax sugar > for (x for x in range(1000, 100))? If you want the integers from 1000 to 100, use: range(1000, 100) Don't waste your time

Re: [Python-ideas] Generator syntax hooks?

On Mon, Aug 7, 2017 at 4:14 PM, Chris Angelico wrote: > On Tue, Aug 8, 2017 at 5:30 AM, Soni L. wrote: > > The generator syntax, (x for x in i if c), currently always creates a new > > generator. that's what it's for -- I'm confused as to what the

Re: [Python-ideas] Generator syntax hooks?

On Tue, Aug 8, 2017 at 5:30 AM, Soni L. wrote: > The generator syntax, (x for x in i if c), currently always creates a new > generator. I find this quite inefficient: > > {x for x in integers if 1000 <= x < 100} # never completes, because it's > trying to iterate over

[Python-ideas] Generator syntax hooks?

The generator syntax, (x for x in i if c), currently always creates a new generator. I find this quite inefficient: {x for x in integers if 1000 <= x < 100} # never completes, because it's trying to iterate over all integers What if, somehow, object `integers` could hook the generator