Mailman 3 April 2021 - Python-Dev

Summary of Python tracker Issues
by Python tracker April 16, 2021

April 16, 2021

ACTIVITY SUMMARY (2021-04-09 - 2021-04-16) Python tracker at https://bugs.python.org/ To view or respond to any of the issues listed below, click on the issue. Do NOT respond to this message. Issues counts and deltas: open 7522 ( -2) closed 48086 (+78) total 55608 (+76) Open issues with patches: 2993 Issues opened (52) ================== #37251: Mocking a MagicMock with a function spec results in an AsyncMo https://bugs.python.org/issue37251 reopened by gregory.p.smith #40066:… [View More]

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Can we change python -W option and PYTHONWARNINGS to use a regex for the message?
by Victor Stinner April 16, 2021

April 16, 2021

Hi, I propose to change the -W command line option and the PYTHONWARNINGS environment variable to use the message as a regular expression in Python 3.10. Or does anyone have a reason to keep the current behavior as it is? I created https://bugs.python.org/issue43862 for this change. -- Python provides two ways to specify warnings filters: * -W command line option: can be used multiple times * PYTHONWARNINGS environment variable: can contain multiple options separated by commas While the … [View More]

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Re: In support of PEP 649
by Tin Tvrtković April 16, 2021

April 16, 2021

Guido: > It seems a little disingenuous to claim discussions about annotations don’t > concern you when you’re actively using them (for typing, no less, in the > case of pydantic). And I am sure a project as popular (by their own > description) as pydantic will find a way forward if PEP 649 is rejected, > despite overdramatized claims. I also maintain a library that uses type annotations in a runtime context (cattrs), but in a slightly different way than Pydantic. My project is … [View More]

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Boundaries between numbers and identifiers
by Serhiy Storchaka April 15, 2021

April 15, 2021

In Python 2.5 `0or[]` was accepted by the Python parser. It became an error in 2.6 because "0o" became recognizing as an incomplete octal number. `1or[]` still is accepted. On other hand, `1if 2else 3` is accepted despites the fact that "2e" can be recognized as an incomplete floating point number. In this case the tokenizer pushes "e" back and returns "2". Shouldn't it do the same with "0o"? It is possible to make `0or[]` be parseable again. Python implementation is able to tokenize … [View More]

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gzip.py: allow deterministic compression (without time stamp)
by Joachim Wuttke April 15, 2021

April 15, 2021

gzip compression, using class GzipFile from gzip.py, by default inserts a timestamp to the compressed stream. If the optional argument `mtime` is absent or None, then the current time is used [1]. This makes outputs non-deterministic, which can badly confuse unsuspecting users: If you run "diff" over two outputs to see whether they are unaffected by changes in your application, then you would not expect that the *.gz binaries differ just because they were created at different times. I'd … [View More]

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Re: Typing syntax and ecosystem, take 2
by Hugh Fisher April 15, 2021

April 15, 2021

> Date: Wed, 14 Apr 2021 09:57:49 +1000 > From: Chris Angelico <rosuav(a)gmail.com> > Subject: [Python-Dev] Re: Typing syntax and ecosystem, take 2 > > You're advocating an approach that absolutely mandates running the > type checker, but then caches the results in an executable file (the > JS file built from the TS source). Python already has a caching system > - the .pyc files - so if you're importing the same file more than > once, the cost of parsing type … [View More]

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Typing syntax and ecosystem, take 2
by Hugh Fisher April 15, 2021

April 15, 2021

In any Python 3.6 or later, type >>> x : float = 1 >>> isinstance(x, float) or replace the second line with >>> type(x) As someone who has programmed in FORTRAN, Pascal, C/C++, Java, and Go this is not at all what I consider reasonable. I do not believe other programmers with experience in typed languages would expect this behaviour either. Having a type checker run before the Python interpreter in our current day continuous build/integration … [View More]

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Re: Typing syntax and ecosystem
by Hugh Fisher April 14, 2021

April 14, 2021

> Date: Wed, 14 Apr 2021 11:24:12 +0200 > From: Antoine Pitrou <antoine(a)python.org> > Subject: [Python-Dev] Re: Typing syntax and ecosystem > > Can you explain why you think C++ typing is based on structural > equivalence? I'd rather not have a detailed discussion of C++ typing on python-dev. My example was Ada style type equivalence by name only, in contrast to Java/C++ style type checking which AFAIK is called "structural equivalence". But if you use another term, … [View More]

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Re: Typing syntax and ecosystem, take 2
by Hugh Fisher April 14, 2021

April 14, 2021

> > Date: Tue, 13 Apr 2021 19:55:38 -0400 > From: Ned Batchelder <ned(a)nedbatchelder.com> > > In another message, you alluded to PEP 649 being a solution to run-time > type checking. Maybe I'm misunderstanding something: type annotations > never do type checking at runtime. As I understand it, PEP 649 is about > avoiding the overhead of evaluating the type expression itself, not > about checking the types of values. Yes, and I see that as a problem. Here are … [View More]

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Re: Revive PEP 396 -- Module Version Numbers ?
by Christopher Barker April 14, 2021

April 14, 2021

Simon, I'm not sure your note made it to the list -- bringing it back on. On Wed, Apr 14, 2021 at 1:15 AM Simon Cross <hodgestar+pythondev(a)gmail.com> wrote: > I would be +1 on having a small PEP like this one to give __version__ > an official blessing and some well-defined expected behaviour. > > I don't have a deep opinion on the specifics of the specification, but > I'm guessing they should be thought about again even if the answers > end up being the same. Quite … [View More]

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Making staticmethod callable, any oposite?
by Inada Naoki April 14, 2021

April 14, 2021

Hi, all. I am implementing PEP 597. During review, Victor suggested to deprecate `OpenWrapper`. `OpenWrapper` is defined only for compatibility between C function and Python function: ``` from _pyio import open as py_open from _io import open as c_open class C: py_open = py_open c_open = c_open C().c_open("README.rst") # works C().py_open("README.rst") # TypeError: expected str, bytes or os.PathLike object, not C ``` So builtin open is not io.open, but io.OpenWrapper in Python 3.… [View More]9. Making staticfunction callable fixes this issue. ``` @staticfunction def open(...): ... ``` Now open defined in Python behaves like C function. We don't need OpenWrapper anymore. This has already been committed by Guido's approval. staticmethod is callable, and OpenWrapper is just an alias of open and deprecated in master branch. But Mark Shannon said we shouldn't make such a change without discussing at python-dev. I don't know we *should*, but I agree that it is *ideal*. Then, does anyone oppose this change? Histrically, this idea had been rejected once. bpo-20309 proposed making classmethod and staticmethod callable. https://bugs.python.org/issue20309 It had been rejected by: "I don't agree that this is a bug that should be fixed. It adds code that will likely never get called or needed (i.e. there has never been a request for this in the decade long history of desciptors and it seems like a made up requirement to me. " https://bugs.python.org/issue20309#msg240843 "actually supporting this would mean adding code that would need to be maintained indefinitely without providing a compensating practical benefit," https://bugs.python.org/issue20309#msg240898 But status is changed now. We already have OpenWrapper. It proves callable classmethod is "called and needed". Although there is only one use case, we can remove more code than adding. staticmethod.__call__() is simple C function. https://github.com/python/cpython/pull/25117/files#diff-57bc77178b3d6f1010d… Victor removed OpenWrapper class already, and we can remove `DocDescripter` too. https://github.com/python/cpython/pull/25354/files#diff-bcdfa9cbb0764d7959c… I think maintenance burden of staticmethod.__call__() is not higher than OpenWrapper and DocDescripter. Additionally, if we have same issue in other module, we can just use staticmethod, instead of copy&paste OpenWrapper and DocDescripter. So it provides "compensating practical benefit". Regards, -- Inada Naoki <songofacandy(a)gmail.com> [View Less]

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0xfor 3. Parser bug?
by Stefano Borini April 14, 2021

April 14, 2021

This was just posted on SO https://stackoverflow.com/questions/67083039/why-does-python-return-15-for-… I can reproduce it with a simpler example >>> 0xfor 3 15 Is it a bug in the parser, or working as intended? It's not only for hex. This works to >>> 3or 50 3 -- Kind regards, Stefano Borini

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Re: Typing syntax and ecosystem, take 2
by Hugh Fisher April 13, 2021

April 13, 2021

> From: Ned Batchelder <ned(a)nedbatchelder.com> [ munch ] > This is very similar to statically typed languages. They also have two > steps: > > * There is the first step that checks the types but does not run the > program. In C/C++, this is the compiler, in Python it is "mypy". > * There is the second step that runs the program but does not check > the types. In C/C++, this is running the executable, in Python it is > "python". > > In … [View More]

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Re: Typing syntax and ecosystem
by jossuazugasti April 12, 2021

April 12, 2021

>> Aren't people allowed to have their own opinions? Absolutely >>>>> If criticism of any current implementation of any construct becomes off-limits is automatically classed as "denigrating" Without judging the particular instance or the discussion itself, here is the definition of the world "ridiculous": Ridiculous: adjective. Deserving or inviting derision or mockery; absurd. I am quite sure that there a better ways to make a technical argument without describing the … [View More]

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Steering Council Q&A.
by Thomas Wouters April 12, 2021

April 12, 2021

As part of our PyCon US talk (which will be pre-recorded), the SC would like to have a Q&A session. Since it's pre-recorded, we figured we'd collect questions through Slido, which also lets people vote on the questions: https://app.sli.do/event/qdtzzpmd. The Slido will be open for questions and voting for a week, after which we'll do our best to answer them all. If you're unhappy using Slido I'd also be happy to take questions directly, but we would like to gauge the popularity of the … [View More]

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Re: Typing syntax and ecosystem
by Hugh Fisher April 12, 2021

April 12, 2021

> Message: 4 > Date: Mon, 12 Apr 2021 13:59:50 -0700 > From: Brett Cannon <brett(a)python.org> > > Please don't denigrate the hard work people have put in to even bring > forward the idea of typing in Python by saying it's "slightly ridiculous". In the interest of moving the discussion forward about separate syntax or type checking integration, I apologize to anyone who feels personally insulted by my response. That was not my intention. -- cheers, Hugh Fisher

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Immutable view classes - inherit from dict or from Mapping?
by Andreas R Maier April 12, 2021

April 12, 2021

Hi, I have written some classes that represent immutable views on collections (see "immutable-views" package on Pypi). Currently, these view classes inherit from the abstract collection classes such as Mapping, Sequence, Set. However, they implement the read-only methods of dict, list and set, which provides some more methods compared to the abstract collection classes. For example, class "dict" provides copy() or __reversed__() and the newer OR-operator methods all of which are not defined on … [View More]

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Please review the new Python Build System documentation
by Victor Stinner April 12, 2021

April 12, 2021

Hi, Please review this documentation: https://docs.python.org/dev/using/configure.html If you have comment, you can directly write a PR (please notify me by mentioning @vstinner in a comment). Or if you prefer, you can reply directly by email and I will try to address your remarks. -- Over the last years, the configure script got more and more options. I was always disappointed by the lack of documentation. It is also really hard to understand how Python pass compiler and linker files … [View More]

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Re: Python Core Mentorship program
by Sheila Bishop April 10, 2021

April 10, 2021

Thanks

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Summary of Python tracker Issues
by Python tracker April 9, 2021

April 9, 2021

ACTIVITY SUMMARY (2021-04-02 - 2021-04-09) Python tracker at https://bugs.python.org/ To view or respond to any of the issues listed below, click on the issue. Do NOT respond to this message. Issues counts and deltas: open 7524 (+19) closed 48008 (+70) total 55532 (+89) Open issues with patches: 2999 Issues opened (60) ================== #24160: Pdb sometimes raises exception when trying to remove a breakpo https://bugs.python.org/issue24160 reopened by pablogsal #39899: `… [View More]

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NamedTemporaryFile and context managers
by Ethan Furman April 9, 2021

April 9, 2021

In issue14243 [1] there are two issues being tracked: - the difference in opening shared files between posix and Windows - the behavior of closing the underlying file in the middle of NamedTemporaryFile's context management I'd like to address and get feedback on the context management issue. ```python from tempfile import NamedTemporaryFile with NamedTemporaryFile() as fp: fp.write(b'some data') fp = open(fp.name()) data = fp.read() assert data == 'some_data' ``` … [View More]

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Re: PEP 647 Accepted
by Federico Salerno April 8, 2021

April 8, 2021

I vaguely remember reading some discussion about Annotated and, for what little it's worth, I disagree with the consensus. For now all that comes to mind is either stuffing the information in docstrings (which would be kind of an involution, seeing as that was the way for annotating type before type annotations), or changing the name of the type to something more obvious at a glance. Something like Typeguards["param", T], if arbitrary strings could be included, which would have to … [View More]correspond to parameter names. This would give a few extra advantages: - Multiple parameters could be annotated per function if needed (e.g. def my_function(param1, param2) -> Typeguards["param1", T, "param2", U]). An alternative syntax could be Typeguards[["param1", T], ["param2", U]] - Functions with additional parameters that the function uses but which are not typeguarded could be used, and there would be no ambiguity as to which parameter is affected by the typeguard: def my_function(param1: Any, param2: bool) -> Typeguards["param1", T] Personally, I like the idea of functions that /happen/ to restrict the type of a variable without it necessarily being their only or primary goal; this would enable those. Possible alternative names: Ensures["param1", T], Ensure["param1", T], IsType["param1", T]. It's important to remember that jargon creates a potential hurdle to comprehension, so simpler language should, in my opinion, always be preferred. Side-note: | is being introduced for union types in type annotations. Could it be an idea to add a & as well, to signal side-effects of the function that do not interfere with the return value? A function could then have a signature like: - def my_function(param1, param2) -> bool & Typeguards["param1", T] - def my_function(param1) -> int & Typeguards[T] # Only one param, so "param1" is optional I realise it would make signatures (optionally!) longer and arguably uglier, but the latter is mostly a matter of personal taster and of getting used to, which is always there when new features are introduced. I remember := being controversial, but it grew on me over time. I hope there's at least something worth considering in the above ideas. On 07/04/2021 21:59, guido(a)python.org wrote: > But it isn't a "side effect". It is a distinct concept that is > important to the type checker. > > Note that in TypeScript this also doesn't look like a boolean -- it > uses a unique syntax that has to be learned: > > function isCustomer(partner: any): partner is Customer { > . . . > } > > Arguably the TS syntax is more easily intuited without looking it up, > but TS has a certain freedom in its syntactic design that we don't > have for Python: new *syntax* has to be added to the Python parser and > can't be backported, whereas new *types* (like `TypeGuard[T]`) can > easily be backported via typing_extensions.py. > > We have really tried, but we did not come up with anything better than > the current PEP. > > FWIW you might be interested in Annotated (PEP 593), which can be used > to indicate various attributes of a type annotation. Before you > suggest that we adopt that instead of PEP 647, we considered that, and > the consensus is that that's not what Annotated is for (it's intended > for conveying information to tools *other* than the type checker, for > example schema checkers etc.). > > -- > --Guido van Rossum (python.org/~guido <http://python.org/~guido>) > /Pronouns: he/him //(why is my pronoun here?)/ > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-…> [View Less]

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Help to Resolve issues with Pull request 25220
by anthony.flury April 8, 2021

April 8, 2021

All, Can someone better than me (i.e anyone) help me resolve the issues with Pull Request 25220. I followed the dev guide, but I assume that between me taking my fork of the cpython repository, and building my pull request, another pull request was merged into master. It also appears that the Documentation build is failing with an rst reference tag error on part of the document I never changed. I am finding it difficult to drive github to understand how to resolve the conflict (i.e how … [View More]

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When we remove 'U' mode of open()?
by Inada Naoki April 8, 2021

April 8, 2021

'U' mode was removed once and resurrected. https://bugs.python.org/issue39674 As far as I can see, it is postponed to Python 3.10. Am I right? Can we remove 'U' mode in Python 3.10? Regards, -- Inada Naoki <songofacandy(a)gmail.com>

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How to attract developer attention to issue tracker items?
by pjfarley3＠earthlink.net April 8, 2021

April 8, 2021

Hi developers, What should / shouldn't I do to attract any python developer response to issue tracker items? I am unsure of the proper procedure to follow so I am asking here first. I have filed two issues on the python issue tracker for python curses issues: 1. # 43715, a documentation update request (suggested additional documentation file uploaded) 2. # 43716, a possible ABI issue for the curses.pair_number() function return value in a Windows environment With respect to the … [View More]

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