Re: Looping [was Re: Python and the need for speed]

On Wed, 11 Oct 2017 10:57 pm, Stefan Ram wrote: > FWIW, in is book "Touch of Class" (2009) Bertrand Meyer writes: > > |Such instructions are just the old goto in sheep's clothing. > |Treat them the same way as the original: > | > |/Touch of Methodology/: > | Sticking to one-entry, one-exit

Re: Looping [was Re: Python and the need for speed]

Chris Angelico writes: > while True: > c = sys.stdin.read(1) > if not c: break > if c.isprintable(): text += c > elif c == "\x08": text = text[:-1] > # etc > Can you write _that_ as a do-while? I prefer to write that sort of thing with iterators: for c in

Re: Looping [was Re: Python and the need for speed]

Op 16-04-17 om 19:07 schreef Terry Reedy: > On 4/16/2017 11:35 AM, Michael Torrie wrote: >> On 04/16/2017 07:57 AM, bartc wrote: >>> But people just don't want it. >>> >>> /That/ is what surprises me, when people reject things that to me are >>> no-brainers. > > Whereas to me, it is a no-brainer

Re: Looping [was Re: Python and the need for speed]

Ben Bacarisse wrote: I fond the proportion on while True: loops surprising. Is there something about Python that encourages that kind of loop? Maybe because for-loops take care of most of the ordinary cases in Python, leaving while-loops to cover the weird ones, many of which need one or

Re: Looping [was Re: Python and the need for speed]

Christian Gollwitzer writes: > Am 18.04.17 um 08:21 schrieb Chris Angelico: >> On Tue, Apr 18, 2017 at 4:06 PM, Christian Gollwitzer >> wrote: >>> Am 18.04.17 um 02:18 schrieb Ben Bacarisse: >>> Thanks (and to Grant). IO seems to be the canonical example. Where some

Re: Looping [was Re: Python and the need for speed]

Am 18.04.17 um 08:21 schrieb Chris Angelico: On Tue, Apr 18, 2017 at 4:06 PM, Christian Gollwitzer wrote: Am 18.04.17 um 02:18 schrieb Ben Bacarisse: Thanks (and to Grant). IO seems to be the canonical example. Where some languages would force one to write c =

Re: Looping [was Re: Python and the need for speed]

Christian Gollwitzer : > Am 18.04.17 um 02:18 schrieb Ben Bacarisse: >> Python opts for >> >> while True: >> c = sys.stdin.read(1) >> if c != ' ': break > > This loop would be the archetypical do..while or repeat...until to me. > > do > c = sys.stdin.read(1) >

Re: Looping [was Re: Python and the need for speed]

On Tue, Apr 18, 2017 at 4:06 PM, Christian Gollwitzer wrote: > Am 18.04.17 um 02:18 schrieb Ben Bacarisse: > >> Thanks (and to Grant). IO seems to be the canonical example. Where >> some languages would force one to write >> >> c = sys.stdin.read(1) >> while c == ' ': >>

Re: Looping [was Re: Python and the need for speed]

Am 18.04.17 um 02:18 schrieb Ben Bacarisse: Thanks (and to Grant). IO seems to be the canonical example. Where some languages would force one to write c = sys.stdin.read(1) while c == ' ': c = sys.stdin.read(1) Python opts for while True: c = sys.stdin.read(1) if c !=

Re: Looping [was Re: Python and the need for speed]

On Tuesday, April 18, 2017 at 2:09:19 AM UTC+1, Paul Rubin wrote: > Ben Bacarisse writes: > > ? I get "AttributeError: 'itertools.dropwhile' object has no attribute > > 'next'" from your example. > > Hmm, .next() worked ok for me in Python 2.7.5. Not sure what happened. > Maybe something went

Re: Looping [was Re: Python and the need for speed]

Ben Bacarisse : > Python opts for > > while True: > c = sys.stdin.read(1) > if c != ' ': break I opt for that in C and bash as well. In fact, when I start writing a loop, I first type: while True: Once it is done, I might notice that the loop

Re: Looping [was Re: Python and the need for speed]

Gregory Ewing : > Marko Rauhamaa wrote: >> What I notice in my numbers is that about one half of my while loops >> are "while True", and about a third of my loops are while loops. > > Out of curiosity, what proportion of your 'while True' loops are > infinite? (I.e.

Re: Looping [was Re: Python and the need for speed]

On Tue, Apr 18, 2017 at 1:37 AM, MRAB wrote: > In Python 3 it's: > > c = next(itertools.dropwhile( > lambda c: c==' ', > iter(lambda: sys.stdin.read(1),None) > )) iter's sentinel should be an empty string. --

Re: Looping [was Re: Python and the need for speed]

On 2017-04-18 02:09, Paul Rubin wrote: Ben Bacarisse writes: ? I get "AttributeError: 'itertools.dropwhile' object has no attribute 'next'" from your example. Hmm, .next() worked ok for me in Python 2.7.5. Not sure what happened. Maybe something went wrong with my

Re: Looping [was Re: Python and the need for speed]

Ben Bacarisse writes: > ? I get "AttributeError: 'itertools.dropwhile' object has no attribute > 'next'" from your example. Hmm, .next() worked ok for me in Python 2.7.5. Not sure what happened. Maybe something went wrong with my paste. Oh well. > Coming from the lazy

Re: Looping [was Re: Python and the need for speed]

Paul Rubin writes: > Ben Bacarisse writes: >> c = sys.stdin.read(1) >> while c == ' ': >> c = sys.stdin.read(1) (for the record: I was not suggesting this was how you'd do it but how you'd be forced to do it in some languages) > c =

Re: Looping [was Re: Python and the need for speed]

On 18/04/2017 01:23, Paul Rubin wrote: Ben Bacarisse writes: c = sys.stdin.read(1) while c == ' ': c = sys.stdin.read(1) c = itertools.dropwhile( lambda c: c==' ', iter(lambda: sys.stdin.read(1),None) ).next() I tried this but it doesn't like

Re: Looping [was Re: Python and the need for speed]

Marko Rauhamaa writes: > Ben Bacarisse : > >> Marko Rauhamaa writes: >>> What I notice in my numbers is that about one half of my while loops >>> are "while True", and about a third of my loops are while loops. >> >> I fo[u]nd the

Re: Looping [was Re: Python and the need for speed]

Ben Bacarisse writes: > c = sys.stdin.read(1) > while c == ' ': > c = sys.stdin.read(1) c = itertools.dropwhile( lambda c: c==' ', iter(lambda: sys.stdin.read(1),None) ).next() -- https://mail.python.org/mailman/listinfo/python-list

Re: Looping [was Re: Python and the need for speed]

Marko Rauhamaa wrote: What I notice in my numbers is that about one half of my while loops are "while True", and about a third of my loops are while loops. Out of curiosity, what proportion of your 'while True' loops are infinite? (I.e. no break, return or raise in the loop.) -- Greg --

Re: Looping [was Re: Python and the need for speed]

On 2017-04-17, Ben Bacarisse wrote: > Marko Rauhamaa writes: > >> Terry Reedy : >> >>> On 4/17/2017 3:11 AM, Marko Rauhamaa wrote: Here's statistics from a medium-sized project of mine: while True:34

Re: Looping [was Re: Python and the need for speed]

On 17 April 2017 at 04:00, Steve D'Aprano wrote: > On Mon, 17 Apr 2017 05:49 am, Dennis Lee Bieber wrote: > >> On Mon, 17 Apr 2017 02:48:08 +1000, Steve D'Aprano >> declaimed the following: >> >>>On Sun, 16 Apr 2017 11:57 pm, bartc wrote:

Re: Looping [was Re: Python and the need for speed]

Ben Bacarisse : > Marko Rauhamaa writes: >> What I notice in my numbers is that about one half of my while loops >> are "while True", and about a third of my loops are while loops. > > I fo[u]nd the proportion on while True: loops surprising. Is there >

Re: Looping [was Re: Python and the need for speed]

On 17/04/2017 19:02, Ben Bacarisse wrote: Marko Rauhamaa writes: Terry Reedy : On 4/17/2017 3:11 AM, Marko Rauhamaa wrote: Here's statistics from a medium-sized project of mine: while True:34 while : 39 for ... in ...: 158

Re: Looping [was Re: Python and the need for speed]

Marko Rauhamaa writes: > Terry Reedy : > >> On 4/17/2017 3:11 AM, Marko Rauhamaa wrote: >>> Here's statistics from a medium-sized project of mine: >>> >>>while True:34 >>>while : 39 >>>for ... in ...: 158 >> >> As I posted

Re: Looping [was Re: Python and the need for speed]

Terry Reedy : > On 4/17/2017 3:11 AM, Marko Rauhamaa wrote: >> Here's statistics from a medium-sized project of mine: >> >>while True:34 >>while : 39 >>for ... in ...: 158 > > As I posted previously, the ratio of for-loops in the stdlib is about

Re: Looping [was Re: Python and the need for speed]

On 4/17/2017 3:11 AM, Marko Rauhamaa wrote: Gregory Ewing : bartc wrote: Most of my loops start off as endless loops, until I can determine the actual terminating condition, and where it best goes. Interesting. My experience is quite different. Most of the loops

Re: Looping [was Re: Python and the need for speed]

Gregory Ewing : > bartc wrote: >> Most of my loops start off as endless loops, until I can determine >> the actual terminating condition, and where it best goes. > > Interesting. My experience is quite different. Most of the loops I > write start off with me thinking

Re: Looping [was Re: Python and the need for speed]

On Mon, 17 Apr 2017 05:49 am, Dennis Lee Bieber wrote: > On Mon, 17 Apr 2017 02:48:08 +1000, Steve D'Aprano > declaimed the following: > >>On Sun, 16 Apr 2017 11:57 pm, bartc wrote: >> >>> But people just don't want it. >> >>Damn straight. Now you get it. It's not

Re: Looping [was Re: Python and the need for speed]

bartc wrote: > - describing the various syntax forms; > - explaining how they differ; > - tutorials for beginners showing each form; And you don't have to explain how an endless loop should be written as 'while True', meanwhile advising against using 'while 1'? You don't have to mention

Re: Looping [was Re: Python and the need for speed]

On 16/04/2017 19:42, Chris Angelico wrote: On Mon, Apr 17, 2017 at 4:21 AM, bartc wrote: Here is a function from some old CPython source that appears to be something to do with While statements: static int validate_while(node *tree) { ... Look, no comments! Are you going to

Re: Looping [was Re: Python and the need for speed]

On Mon, Apr 17, 2017 at 4:21 AM, bartc wrote: > Here is a function from some old CPython source that appears to be something > to do with While statements: > > static int > validate_while(node *tree) > { > int nch = NCH(tree); > int res = (validate_ntype(tree, while_stmt)

Re: Looping [was Re: Python and the need for speed]

On 16/04/2017 17:30, Steve D'Aprano wrote: On Sun, 16 Apr 2017 10:06 pm, bartc wrote: (The 30 Loc figure is with support for loops /in general/ already in place, and is for /adding/ a new loop statement, in this case 'while') What part of *testing* and *documenting* do you not understand?

Re: Looping [was Re: Python and the need for speed]

On Mon, 17 Apr 2017 03:00 am, Rustom Mody wrote: > BTW I regard Steven's long list of things that youve missed such as > regression tests, docs etc to be somewhat off the mark > To see that try this experiment: > Just add a feature to python that matters to you along with all these >

Re: Looping [was Re: Python and the need for speed]

On 4/16/2017 11:35 AM, Michael Torrie wrote: On 04/16/2017 07:57 AM, bartc wrote: But people just don't want it. /That/ is what surprises me, when people reject things that to me are no-brainers. Whereas to me, it is a no-brainer that we are better off *without* multiple while/loop

Re: Looping [was Re: Python and the need for speed]

On Sunday, April 16, 2017 at 7:27:49 PM UTC+5:30, bartc wrote: > Technically, adding this one feature to Python /is/ trivial, ^ You are not paying attention bart and I am not likely to pursue this beyond this post. I tried to say as are others that the substantive reasons to reject a

Re: Looping [was Re: Python and the need for speed]

On Sun, 16 Apr 2017 11:57 pm, bartc wrote: > Yet countless other, far more elaborate features /are/ added all the time. Indeed. Because they are needed. Because they add functionality that Python doesn't already have, or seriously improves the interface to that functionality. > Technically,

Re: Looping [was Re: Python and the need for speed]

On Sun, 16 Apr 2017 10:06 pm, bartc wrote: > On 16/04/2017 03:51, Steve D'Aprano wrote: >> On Sat, 15 Apr 2017 10:17 pm, bartc wrote: > >>> Yes, I'm constantly surprised at this, as such syntax has a very low >>> cost (in my last compiler, supporting 'while' for example only added 30 >>> lines

Re: Looping [was Re: Python and the need for speed]

On 16/04/2017 15:22, Chris Angelico wrote: On Sun, Apr 16, 2017 at 11:57 PM, bartc wrote: Technically, adding this one feature to Python /is/ trivial, for example, allowing while: as a synonym for while True:, but preferably using a new keyword such as loop. Nothing else needs

Re: Looping [was Re: Python and the need for speed]

On 04/16/2017 07:57 AM, bartc wrote: > But people just don't want it. > > /That/ is what surprises me, when people reject things that to me are > no-brainers. I simply don't care about these missing loop constructs. Python works great for what I use it for, and apparently works well for many

Re: Looping [was Re: Python and the need for speed]

On Sun, Apr 16, 2017 at 11:57 PM, bartc wrote: > Technically, adding this one feature to Python /is/ trivial, for example, > allowing while: as a synonym for while True:, but preferably using a new > keyword such as loop. Nothing else needs to be touched. And it could have > been

Re: Looping [was Re: Python and the need for speed]

On 16/04/2017 13:22, Rustom Mody wrote: On Sunday, April 16, 2017 at 5:36:28 PM UTC+5:30, bartc wrote: On 16/04/2017 03:51, Steve D'Aprano wrote: On Sat, 15 Apr 2017 10:17 pm, bartc wrote: Yes, I'm constantly surprised at this, as such syntax has a very low cost (in my last compiler,

Re: Looping [was Re: Python and the need for speed]

On Sunday, April 16, 2017 at 5:36:28 PM UTC+5:30, bartc wrote: > On 16/04/2017 03:51, Steve D'Aprano wrote: > > On Sat, 15 Apr 2017 10:17 pm, bartc wrote: > > >> Yes, I'm constantly surprised at this, as such syntax has a very low > >> cost (in my last compiler, supporting 'while' for example

Re: Looping [was Re: Python and the need for speed]

On 16/04/2017 03:51, Steve D'Aprano wrote: On Sat, 15 Apr 2017 10:17 pm, bartc wrote: Yes, I'm constantly surprised at this, as such syntax has a very low cost (in my last compiler, supporting 'while' for example only added 30 lines to the project). That's the advantage of writing your own

Re: Looping [was Re: Python and the need for speed]

Steve D'Aprano writes: > I don't remember the language, but I remember seeing one generalisation of > the repeat/do loop that puts the test in the middle, rather than at the > start or end of the loop. If I remember it was something like: > > DO > setup code #

Looping [was Re: Python and the need for speed]

On Sat, 15 Apr 2017 10:17 pm, bartc wrote: > On 15/04/2017 03:35, Rick Johnson wrote: >> On Wednesday, April 12, 2017 at 8:44:30 AM UTC-5, bart...@gmail.com >> wrote: > >> At a minimum, every language should offer >> the following four loop-forms (using Python semantics): >> >> while