Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Let's not change pprint. On Fri, Dec 22, 2017 at 7:44 AM, Eric Fahlgren wrote: > On Thu, Dec 21, 2017 at 7:51 PM, Stephen J. Turnbull < > turnbull.stephen...@u.tsukuba.ac.jp> wrote: > >> I understand the motivation to guarantee order, but it's a programmer >> convenience

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Thu, Dec 21, 2017 at 7:51 PM, Stephen J. Turnbull < turnbull.stephen...@u.tsukuba.ac.jp> wrote: > I understand the motivation to guarantee order, but it's a programmer > convenience that has nothing to do with the idea of mapping, and the > particular (insertion) order is very special and

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Chris Barker writes: > Nathaniel Smith has pointed out that eval(pprint(a_dict)) is > supposed to return the same dict -- so documented behavior may > already be broken. Sure, but that's because we put shoes on a snake. Why anybody expects no impediment to slithering, I don't know! I

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Wed, Dec 20, 2017 at 03:23:16PM -0800, Chris Barker wrote: > On Wed, Dec 20, 2017 at 2:31 AM, Steven D'Aprano > wrote: > > Even when it works, the guarantee is quite weak. For instance, even > > the object type is not preserved: > > > > py> class MyDict(dict): > > ...

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 08:49:54PM -0800, Nathaniel Smith wrote: > On Mon, Dec 18, 2017 at 7:58 PM, Steven D'Aprano wrote: > > I have a script which today prints data like so: [...] > To make sure I understand, do you actually have a script like this, or > is this

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, 19 Dec 2017 17:32:52 -0800 Nathaniel Smith wrote: > > > In any case, there are so many ways > > to spoil the first point for yourself that it's hardly worth treating as an > > important constraint. > > I guess the underlying issue here is partly the question of what

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Dec 19, 2017 at 04:56:16PM -0800, Steve Dower wrote: > On 19Dec2017 1004, Chris Barker wrote: > >(though I assume order is still ignored when comparing dicts, so: > >eval(pprint(a_dict)) == a_dict will still hold. > > Order had better be ignored when comparing dicts, or plenty of code

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 12/19/2017 5:32 PM, Nathaniel Smith wrote: On Tue, Dec 19, 2017 at 4:56 PM, Steve Dower wrote: On 19Dec2017 1004, Chris Barker wrote: Nathaniel Smith has pointed out that eval(pprint(a_dict)) is supposed to return the same dict -- so documented behavior may already

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Dec 19, 2017, at 20:32, Nathaniel Smith wrote: > I guess the underlying issue here is partly the question of what the > pprint module is for. In my understanding, it's primarily a tool for > debugging/introspecting Python programs, and the reason it talks about > "valid input

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Dec 19, 2017 at 4:56 PM, Steve Dower wrote: > On 19Dec2017 1004, Chris Barker wrote: >> >> Nathaniel Smith has pointed out that eval(pprint(a_dict)) is supposed to >> return the same dict -- so documented behavior may already be broken. > > > Two relevant quotes

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 19Dec2017 1004, Chris Barker wrote: Nathaniel Smith has pointed out that eval(pprint(a_dict)) is supposed to return the same dict -- so documented behavior may already be broken. Two relevant quotes from the pprint module docs: >>> The pprint module provides a capability to “pretty-print”

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 19 December 2017 at 17:57, Steve Holden wrote: > On Tue, Dec 19, 2017 at 4:49 PM, Stephen J. Turnbull > wrote: >> >> Nathaniel Smith writes: >> >> > To make sure I understand, do you actually have a script like this, or >> > is this

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Dec 19, 2017 at 8:14 AM, Barry Warsaw wrote: > On Dec 18, 2017, at 22:37, Nathaniel Smith wrote: > > > Wait, what? Why would changing pprint (so that it accurately reflects > > dict's new underlying semantics!) be a breaking change? Are you > >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Dec 19, 2017 at 4:49 PM, Stephen J. Turnbull < turnbull.stephen...@u.tsukuba.ac.jp> wrote: > Nathaniel Smith writes: > > > To make sure I understand, do you actually have a script like this, or > > is this hypothetical? > > I have a couple of doctests that assume that pprint will sort

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Nathaniel Smith writes: > To make sure I understand, do you actually have a script like this, or > is this hypothetical? I have a couple of doctests that assume that pprint will sort by key, yes. It makes the tests look quite a bit nicer by pprinting the output, and I get sorting (which

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Dec 18, 2017, at 22:37, Nathaniel Smith wrote: > Wait, what? Why would changing pprint (so that it accurately reflects > dict's new underlying semantics!) be a breaking change? Are you > suggesting it shouldn't be changed in 3.7? As others have pointed out, exactly because

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 19 December 2017 at 08:27, Nathaniel Smith wrote: > On Mon, Dec 18, 2017 at 11:38 PM, Steve Dower wrote: >> On 18Dec2017 2309, Steven D'Aprano wrote: >>> [A LOT OF THINGS I AGREE WITH] >> I agree completely with Steven's reasoning here, and it bothers

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 11:38 PM, Steve Dower wrote: > On 18Dec2017 2309, Steven D'Aprano wrote: >> [A LOT OF THINGS I AGREE WITH] > I agree completely with Steven's reasoning here, and it bothers me that > what is an irrelevant change to many users (dict becoming ordered)

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 12/19/2017 2:38 AM, Steve Dower wrote: On 18Dec2017 2309, Steven D'Aprano wrote: [A LOT OF THINGS I AGREE WITH] I agree completely with Steven's reasoning here, and it bothers me that what is an irrelevant change to many users (dict becoming ordered) seems to imply that all users of dict

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 18Dec2017 2309, Steven D'Aprano wrote: > [A LOT OF THINGS I AGREE WITH] I agree completely with Steven's reasoning here, and it bothers me that what is an irrelevant change to many users (dict becoming ordered) seems to imply that all users of dict have to be updated. I have never needed

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Dec 19, 2017 at 6:09 PM, Steven D'Aprano wrote: > I completely agree. We might argue that it was a mistake to sort dicts > in the first place, or at least a mistake to *always* sort them without > allowing the caller to provide a sort key. But what's done is done: the

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 08:28:52PM -0800, Chris Barker wrote: > On Mon, Dec 18, 2017 at 7:41 PM, Steven D'Aprano > wrote: > > > > With arbitrary order, it made sense to sort, so as to always give the > > same > > > "pretty" representation. But now that order is "part of" the

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 7:58 PM, Steven D'Aprano wrote: > On Mon, Dec 18, 2017 at 07:37:03PM -0800, Nathaniel Smith wrote: >> On Mon, Dec 18, 2017 at 7:02 PM, Barry Warsaw wrote: >> > On Dec 18, 2017, at 21:11, Chris Barker wrote: >>

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 7:41 PM, Steven D'Aprano wrote: > > With arbitrary order, it made sense to sort, so as to always give the > same > > "pretty" representation. But now that order is "part of" the dict itself, > > it seems prettyprint should present the preserved order

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 07:37:03PM -0800, Nathaniel Smith wrote: > On Mon, Dec 18, 2017 at 7:02 PM, Barry Warsaw wrote: > > On Dec 18, 2017, at 21:11, Chris Barker wrote: > > > >> Will changing pprint be considered a breaking change? > > > > Yes,

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 06:11:05PM -0800, Chris Barker wrote: > Now that dicts are order-preserving, maybe we should change prettyprint: > > In [7]: d = {'one':1, 'two':2, 'three':3} > > In [8]: print(d) > {'one': 1, 'two': 2, 'three': 3} > > order preserved. > > In [9]: pprint.pprint(d) >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Dec 18, 2017 at 7:02 PM, Barry Warsaw wrote: > On Dec 18, 2017, at 21:11, Chris Barker wrote: > >> Will changing pprint be considered a breaking change? > > Yes, definitely. Wait, what? Why would changing pprint (so that it accurately reflects

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Dec 18, 2017, at 21:11, Chris Barker wrote: > Will changing pprint be considered a breaking change? Yes, definitely. -Barry signature.asc Description: Message signed with OpenPGP ___ Python-Dev mailing list

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Now that dicts are order-preserving, maybe we should change prettyprint: In [7]: d = {'one':1, 'two':2, 'three':3} In [8]: print(d) {'one': 1, 'two': 2, 'three': 3} order preserved. In [9]: pprint.pprint(d) {'one': 1, 'three': 3, 'two': 2} order not preserved ( sorted, I presume? ) With

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Fri, Dec 15, 2017 at 9:47 PM, Guido van Rossum wrote: > ​[...] > > stays ordered across deletions" part of the ruling is true in CPython 3.6. > > I don't know what guidance to give Eric, because I don't know what other > implementations do nor whether Eric cares about

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Cool, thanks! I'm curious why this was brought up at all then... On Dec 15, 2017 3:36 PM, "Raymond Hettinger" wrote: > > > > On Dec 15, 2017, at 1:47 PM, Guido van Rossum wrote: > > > > On Fri, Dec 15, 2017 at 12:45 PM, Raymond Hettinger < >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> On Dec 15, 2017, at 1:47 PM, Guido van Rossum wrote: > > On Fri, Dec 15, 2017 at 12:45 PM, Raymond Hettinger > wrote: > > > On Dec 15, 2017, at 7:53 AM, Guido van Rossum wrote: > > > > Make it so. "Dict keeps insertion

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Fri, Dec 15, 2017 at 12:45 PM, Raymond Hettinger < raymond.hettin...@gmail.com> wrote: > > > On Dec 15, 2017, at 7:53 AM, Guido van Rossum wrote: > > > > Make it so. "Dict keeps insertion order" is the ruling. > > On Twitter, someone raised an interesting question. > > Is

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> On Dec 15, 2017, at 7:53 AM, Guido van Rossum wrote: > > Make it so. "Dict keeps insertion order" is the ruling. On Twitter, someone raised an interesting question. Is the guarantee just for 3.7 and later? Or will the blessing also cover 3.6 where it is already true.

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Dec 15, 2017 10:50, "Tim Peters" wrote: [Eric Snow ] > Does that include preserving order after deletion? Given that we're blessing current behavior: - At any moment, iteration order is from oldest to newest. So, "yes" to your question. -

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

[Eric Snow ] > Does that include preserving order after deletion? Given that we're blessing current behavior: - At any moment, iteration order is from oldest to newest. So, "yes" to your question. - While iteration starts with the oldest, .popitem() returns the

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Fri, Dec 15, 2017 at 10:30 AM, Eric Snow wrote: > On Fri, Dec 15, 2017 at 8:53 AM, Guido van Rossum > wrote: > > Make it so. "Dict keeps insertion order" is the ruling. Thanks! > > Does that include preserving order after deletion? Yes, that's

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Fri, Dec 15, 2017 at 8:53 AM, Guido van Rossum wrote: > Make it so. "Dict keeps insertion order" is the ruling. Thanks! Does that include preserving order after deletion? -eric ___ Python-Dev mailing list Python-Dev@python.org

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 15 December 2017 at 18:19, Serhiy Storchaka wrote: > 15.12.17 17:53, Guido van Rossum пише: >> >> Make it so. "Dict keeps insertion order" is the ruling. Thanks! > > What should dict.popitem() return? The first item, the last item, or > unspecified? I'd say leave it as

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Whatever it does in 3.6. On Fri, Dec 15, 2017 at 10:19 AM, Serhiy Storchaka wrote: > 15.12.17 17:53, Guido van Rossum пише: > >> Make it so. "Dict keeps insertion order" is the ruling. Thanks! >> > > What should dict.popitem() return? The first item, the last item, or >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

15.12.17 17:53, Guido van Rossum пише: Make it so. "Dict keeps insertion order" is the ruling. Thanks! What should dict.popitem() return? The first item, the last item, or unspecified? ___ Python-Dev mailing list Python-Dev@python.org

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 12/15/2017 11:55 AM, Guido van Rossum wrote: On Fri, Dec 15, 2017 at 8:32 AM, Raymond Hettinger > wrote: > On Dec 15, 2017, at 7:53 AM, Guido van Rossum > wrote: > >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Fri, Dec 15, 2017 at 8:32 AM, Raymond Hettinger < raymond.hettin...@gmail.com> wrote: > > > On Dec 15, 2017, at 7:53 AM, Guido van Rossum wrote: > > > > Make it so. "Dict keeps insertion order" is the ruling. Thanks! > > Thank you. That is wonderful news :-) > > Would it be

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> On Dec 15, 2017, at 7:53 AM, Guido van Rossum wrote: > > Make it so. "Dict keeps insertion order" is the ruling. Thanks! Thank you. That is wonderful news :-) Would it be reasonable to replace some of the OrderedDict() uses in the standard library with dict()? For

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Make it so. "Dict keeps insertion order" is the ruling. Thanks! On Fri, Dec 15, 2017 at 2:30 AM, INADA Naoki wrote: > > That's interesting information - I wasn't aware of the different > > performance goals. > > FYI, performance characteristic of my POC implementation of

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> That's interesting information - I wasn't aware of the different > performance goals. FYI, performance characteristic of my POC implementation of OrderedDict based on dict order are: * 50% less memory usage * 15% faster creation * 100% (2x) faster iteration * 20% slower move_to_end * 40%

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 15 December 2017 at 05:28, Raymond Hettinger wrote: > In contrast, I gave collections.OrderedDict a different design (later coded > in C by Eric Snow). The primary goal was to have efficient maintenance of > order even for severe workloads such at that imposed

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> I support having regular dicts maintain insertion order but am opposed to > Inada changing the implementation of collections.OrderedDict We can have > the first without having the second. > > It seems like the two quoted paragraphs are in vociferous agreement. The referenced tracker entry

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Dec 14, 2017 21:30, "Raymond Hettinger" wrote: > On Dec 14, 2017, at 6:03 PM, INADA Naoki wrote: > > If "dict keeps insertion order" is not language spec and we > continue to recommend people to use OrderedDict to keep > order, I want to

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> On Dec 14, 2017, at 6:03 PM, INADA Naoki wrote: > > If "dict keeps insertion order" is not language spec and we > continue to recommend people to use OrderedDict to keep > order, I want to optimize OrderedDict for creation/iteration > and memory usage. (See

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Oh, I just found https://mail.python.org/pipermail/python-dev/2017-November/150323.html so I already know what you think: we should go with "dicts preserve insertion order" rather than "dicts preserve insertion order until the first deletion". I guess we should wait for Serhiy to confirm that he's

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

I'm in favor of stating that dict keeps order as part of the language spec. However re-reading https://mail.python.org/pipermail/python-dev/2017-November/150381.html there's still a point of debate: should it be allowed if dict reorders after deletion (presumably as a result of a rehash)? I'm in

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hi, folks. TLDR, was the final decision made already? If "dict keeps insertion order" is not language spec and we continue to recommend people to use OrderedDict to keep order, I want to optimize OrderedDict for creation/iteration and memory usage. (See

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

08.11.17 04:33, Nick Coghlan пише: On 8 November 2017 at 11:44, Nick Coghlan wrote: 2. So far, I haven't actually come up with a perturbed iteration implementation that doesn't segfault the interpreter. The dict internals are nicely laid out to be iteration friendly, but

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

It seems there must be at least two threads for each topic worth discussing at all. Therefore I feel compelled to point to https://mail.python.org/pipermail/python-dev/2017-November/150381.html, where I state my own conclusion about dict order. I know Paul Sokolovsky does not claim to speak for

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Wed, Nov 8, 2017 at 5:35 AM, Paul G wrote: > If dictionary order is *not* guaranteed in the spec and the dictionary order > isn't randomized (which I think everyone agrees is a bit messed up), it would > probably be useful if you could enable "random order mode" in CPython,

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> 2. Switches keyword args and class body execution namespaces over to > odict so the test suite passes again > 3. Measures the impact such a change would have on the benchmark suite For now, odict use twice memory and 2x slower on iteration. https://bugs.python.org/issue31265#msg301942 INADA

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 8 November 2017 at 11:44, Nick Coghlan wrote: > 2. So far, I haven't actually come up with a perturbed iteration > implementation that doesn't segfault the interpreter. The dict > internals are nicely laid out to be iteration friendly, but they > really do assume that

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 7, 2017, at 16:15, Chris Barker - NOAA Federal wrote: > Actually, there is a LOT of code out there that expects reference counting. I > know a lot of my code does. So if cPython does abandon it some day, there > will be issues. I see this all the time in code

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 8 November 2017 at 07:15, Paul Moore wrote: > On 7 November 2017 at 20:35, Paul G wrote: >> If dictionary order is *not* guaranteed in the spec and the dictionary order >> isn't randomized (which I think everyone agrees is a bit messed up), it >> would

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> By the way, I only just realized I can delete a key to demonstrate > non-order-preservation on py 3.6. So at least I know what to tell students > now. > You can't. dict in Python 3.6 preserves insertion order even after key deletion. ___ Python-Dev

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

This seems like overkill to me. By the same logic, we should add a "delay garbage collection" mode, that allows people to test that their code doesn't make unwarranted assumptions that a reference-counting garbage collector is in use. Actually, there is a LOT of code out there that expects

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

@ Paul Moore > This seems like overkill to me. By the same logic, we should add a > "delay garbage collection" mode, that allows people to test that their > code doesn't make unwarranted assumptions that a reference-counting > garbage collector is in use. But you can get pretty fine-grained

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 21:13, Chris Barker wrote: > the "only until first deletion" part is really hard -- I hope we don't go > that route. But I don't think insertion-order is non-obvious -- particularly > with literals. But I thought we *had* gone that route. Actually,

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 7, 2017, at 12:35, Paul G wrote: > > If dictionary order is *not* guaranteed in the spec and the dictionary order > isn't randomized (which I think everyone agrees is a bit messed up), it would > probably be useful if you could enable "random order mode" in CPython, so

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 20:35, Paul G wrote: > If dictionary order is *not* guaranteed in the spec and the dictionary order > isn't randomized (which I think everyone agrees is a bit messed up), it would > probably be useful if you could enable "random order mode" in CPython, so

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Nov 7, 2017 at 7:21 AM, David Mertz wrote: > But like Raymond, I make most of my living TEACHING Python. > and I make least of my living TEACHING Python ( :-) ),and: > I feel like the extra order guarantee would make teaching slightly harder. > I can't understand how

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

If dictionary order is *not* guaranteed in the spec and the dictionary order isn't randomized (which I think everyone agrees is a bit messed up), it would probably be useful if you could enable "random order mode" in CPython, so you can stress-test that your code isn't making any assumptions

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 7, 2017 12:02 PM, "Barry Warsaw" wrote: On Nov 7, 2017, at 09:39, Paul Sokolovsky wrote: > So, the problem is that there's no "Python language spec”. There is a language specification: https://docs.python.org/3/refe rence/index.html But there are

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 7, 2017, at 09:39, Paul Sokolovsky wrote: > So, the problem is that there's no "Python language spec”. There is a language specification: https://docs.python.org/3/reference/index.html But there are still corners that are undocumented, or topics that are

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 07/11/17 04:05, David Mertz wrote: I strongly opposed adding an ordered guarantee to regular dicts. If the implementation happens to keep that, great. Maybe OrderedDict can be rewritten to use the dict implementation. But the evidence that all implementations will always be fine with this

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hello, On Tue, 7 Nov 2017 14:40:07 +0900 INADA Naoki wrote: > I agree with Raymond. dict ordered by default makes better developer > experience. > > So, my concern is how "language spec" is important for minor (sorry > about my bad vocabulary) implementation? > What's

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hello, On Tue, 7 Nov 2017 17:33:03 +1100 Steven D'Aprano wrote: > On Mon, Nov 06, 2017 at 06:35:48PM +0200, Paul Sokolovsky wrote: > > > For MicroPython, it would lead to quite an overhead to make > > dictionary items be in insertion order. As I mentioned, MicroPython > >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 7, 2017, at 01:51, Petr Viktorin wrote: > > When I explained this in 3.5, dicts rearranging themselves seemed quite weird > to the newcomers. > This year, I'm not looking forward to saying that dicts behave "intuitively", > but you shouldn't rely on that, because

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 6, 2017, at 22:33, Steven D'Aprano wrote: > I think it would be reasonable to say that builtin dicts only maintain > insertion order for insertions, lookups, and changing the value. Any > mutation which deletes keys may arbitrarily re-order the dict. > > If the user

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 6, 2017 9:11 PM, "Raymond Hettinger" wrote: > On Nov 6, 2017, at 8:05 PM, David Mertz wrote: > I strongly opposed adding an ordered guarantee to regular dicts. If the implementation happens to keep that, great. Maybe OrderedDict can be

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 11/07/2017 09:00 AM, Wolfgang wrote: > Hi, > > I have to admit sometimes I don't understand why small things produce so much > mail traffic. :-) > > If I use a mapping like dict most of the time I don't care if it is ordered. > If I need an ordering I use OrderedDict. In a library if I need a

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hello, I agree with Wolfgang here. From what I gathered of the discussion, the argument started from « It would be nice if dict litterals returned ordered dicts instead of an unordered ones », which is mostly a good thing, as it allows e.g. `OrderedDict({'spam': 'ham', 'sausages': 'eggs'})`

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, 2017-11-07 at 16:39 +1000, Nick Coghlan wrote: > And this is the key point for me: "choosing not to choose" is > effectively the same as standardising the feature, as enough Python > code will come to rely on CPython's behaviour that most alternative > implementations will feel obliged to

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 06:39, Nick Coghlan wrote: > On 7 November 2017 at 09:23, Chris Barker wrote: >> in short -- we don't have a choice (unless we add an explicit randomization >> as some suggested -- but that just seems perverse...) > > And this is

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 11/07/2017 09:00 AM, Wolfgang wrote: [...] Also it is fine to teach people that dict (Mapping) is not ordered but CPython has an implementation detail and it is ordered. But if you want the guarantee use OrderedDict. I don't think that is fine. When I explained this in 3.5, dicts

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hi, I have to admit sometimes I don't understand why small things produce so much mail traffic. :-) If I use a mapping like dict most of the time I don't care if it is ordered. If I need an ordering I use OrderedDict. In a library if I need a dict to be ordered most of the time there is a

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Tue, Nov 07, 2017 at 05:28:24PM +1000, Nick Coghlan wrote: > On 7 November 2017 at 16:21, Steven D'Aprano wrote: > > On Mon, Nov 06, 2017 at 08:05:07PM -0800, David Mertz wrote: > >> Maybe OrderedDict can be > >> rewritten to use the dict implementation. But the evidence

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 16:21, Steven D'Aprano wrote: > On Mon, Nov 06, 2017 at 08:05:07PM -0800, David Mertz wrote: >> Maybe OrderedDict can be >> rewritten to use the dict implementation. But the evidence that all >> implementations will always be fine with this restraint

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 09:23, Chris Barker wrote: > in short -- we don't have a choice (unless we add an explicit randomization > as some suggested -- but that just seems perverse...) And this is the key point for me: "choosing not to choose" is effectively the same as

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 06, 2017 at 10:17:23PM -0200, Joao S. O. Bueno wrote: > And also, forgot along the discussion, is the big disadvantage that > other Python implementations would have a quite > significant overhead on mandatory ordered dicts. I don't think that is correct. Nick already did a survey,

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 06, 2017 at 06:35:48PM +0200, Paul Sokolovsky wrote: > For MicroPython, it would lead to quite an overhead to make > dictionary items be in insertion order. As I mentioned, MicroPython > optimizes for very low bookkeeping memory overhead, so lookups are > effectively O(n), but

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 06, 2017 at 08:05:07PM -0800, David Mertz wrote: > I strongly opposed adding an ordered guarantee to regular dicts. If the > implementation happens to keep that, great. That's the worst of both worlds. The status quo is that unless we deliberately perturb the dictionary order,

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 7 November 2017 at 03:27, Chris Jerdonek wrote: > On Mon, Nov 6, 2017 at 4:11 AM Nick Coghlan wrote: >> Getting from the "Works on CPython 3.6+ but is technically >> non-portable" state to a fully portable correct implementation that >> ensures a

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

I agree with Raymond. dict ordered by default makes better developer experience. So, my concern is how "language spec" is important for minor (sorry about my bad vocabulary) implementation? What's difference between "MicroPython is 100% compatible with language spec" and "MicroPython is almost

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

> On Nov 6, 2017, at 8:05 PM, David Mertz wrote: > > I strongly opposed adding an ordered guarantee to regular dicts. If the > implementation happens to keep that, great. Maybe OrderedDict can be > rewritten to use the dict implementation. But the evidence that all >

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 06, 2017 at 11:33:10AM -0800, Barry Warsaw wrote: > If we did make the change, it’s possible we would need a way to > explicit say that order is not preserved. That seems a little weird > to me, but I suppose it could be useful. Useful for what? Given that we will hypothetically

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

I strongly opposed adding an ordered guarantee to regular dicts. If the implementation happens to keep that, great. Maybe OrderedDict can be rewritten to use the dict implementation. But the evidence that all implementations will always be fine with this restraint feels poor, and we have a

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 06, 2017 at 12:18:17PM +0200, Paul Sokolovsky wrote: > > I don't think that situation should change the decision, > > Indeed, it shouldn't. What may change it is the simple and obvious fact > that there's no need to change anything, as proven by the 25-year > history of the

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, 6 Nov 2017 at 11:08 Paul Sokolovsky wrote: > Hello, > > On Mon, 06 Nov 2017 17:58:47 + > Brett Cannon wrote: > > [] > > > > Why suddenly once in 25 years there's a need to do something to > > > dict's, violating computer science background behind

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On 6 November 2017 at 17:23, Paul G wrote: > Is there a major objection to just adding in explicit syntax for > order-preserving dictionaries? To some extent that seems like a reasonable > compromise position in an "explicit is better than implicit" sense. A whole > lot of

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Mon, Nov 6, 2017 at 11:23 AM, Paul G wrote: > (Of course, given that CPython's implementation is order-preserving, a > bunch of code is probably now being written that implicitly requires on > this detail, but at least having syntax that makes that clear would give > people

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

06.11.17 21:56, Paul Sokolovsky пише: Btw, in all this discussion, I don't remember anyone mentioning sets. I don't recall the way they're implemented in CPython, but they have strong conceptual and semantic resemblance to dict's. So, what about them, do they become ordered too? No, sets are

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

Hello, On Mon, 6 Nov 2017 11:33:10 -0800 Barry Warsaw wrote: [] > If we did make the change, it’s possible we would need a way to > explicit say that order is not preserved. That seems a little weird I recently was working on a more or less complex dataflow propagation

Re: [Python-Dev] Guarantee ordered dict literals in v3.7?

On Nov 6, 2017, at 11:23, Paul G wrote: > > Is there a major objection to just adding in explicit syntax for > order-preserving dictionaries? I don’t think new syntax is necessary. We already have OrderedDict, which to me is a perfectly sensible way to spell “I need a

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