Mailman 3 August 2020 - Python-Dev

async generator bug fixed in 3.8+ and backported to 3.6 but not to 3.7
by Matthew Einhorn 12 Aug '20

12 Aug '20

Hi, The fix for https://bugs.python.org/issue33786 ("@asynccontextmanager doesn't work well with async generators") was merged in 3.8 and then backported to 3.6. However, it was overlooked to be backported for 3.7 ( https://github.com/python/cpython/pull/7506). I'm aware that 3.7 is in security fix mode only so I'm not sure there's more to be done, however, given that this is fixed for 3.6, 3.7 is in a weird position still having the bug. So I just wanted to bring this up in case the fix can still be backported to 3.7. Matt

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How about copying the typing module docs from 3.10 to 3.9?
by Luciano Ramalho 11 Aug '20

11 Aug '20

Hello, Łukasz, I reorganized the typing module docs, Guido made suggestions, reviewed and merged it to master. Right now everything in typing.rst [1] applies to 3.9 as well as 3.10. [1] https://docs.python.org/3.10/library/typing.html How about copying the typing.rst file to the 3.9 branch, so more people would benefit from it sooner? Cheers, Luciano -- Luciano Ramalho | Author of Fluent Python (O'Reilly, 2015) | http://shop.oreilly.com/product/0636920032519.do | Technical Principal at ThoughtWorks | Twitter: @ramalhoorg

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[RELEASE] Python 3.9.0rc1 is now available
by Łukasz Langa 11 Aug '20

11 Aug '20

Python 3.9.0 is *almost* ready. This release, *3.9.0rc1*, is the penultimate release preview. You can get it here: https://www.python.org/downloads/release/python-390rc1/ Entering the release candidate phase, only reviewed code changes which are clear bug fixes are allowed between this release candidate and the final release. The second candidate and the last planned release preview is currently planned for 2020-09-14. Please keep in mind that this is a preview release and its use is *not* recommended for production environments. Calls to action Core developers: all eyes on the docs now * Are all *your* changes properly documented? * Did you notice *other* changes you know of to have insufficient documentation? Community members We *strongly encourage* maintainers of third-party Python projects to prepare their projects for 3.9 compatibility during this phase. As always, report any issues to the Python bug tracker <https://bugs.python.org/>. Installer news This is the first version of Python to default to the 64-bit installer on Windows. The installer now also actively disallows installation on Windows 7. Python 3.9 is incompatible with this unsupported version of Windows. Major new features of the 3.9 series, compared to 3.8 Some of the new major new features and changes in Python 3.9 are: * PEP 584 <https://www.python.org/dev/peps/pep-0584/>, Union Operators in `dict` * PEP 585 <https://www.python.org/dev/peps/pep-0585/>, Type Hinting Generics In Standard Collections * PEP 593 <https://www.python.org/dev/peps/pep-0593/>, Flexible function and variable annotations * PEP 602 <https://www.python.org/dev/peps/pep-0602/>, Python adopts a stable annual release cadence * PEP 615 <https://www.python.org/dev/peps/pep-0615/>, Support for the IANA Time Zone Database in the Standard Library * PEP 616 <https://www.python.org/dev/peps/pep-0616/>, String methods to remove prefixes and suffixes * PEP 617 <https://www.python.org/dev/peps/pep-0617/>, New PEG parser for CPython * BPO 38379 <https://bugs.python.org/issue38379>, garbage collection does not block on resurrected objects; * BPO 38692 <https://bugs.python.org/issue38692>, os.pidfd_open added that allows process management without races and signals; * BPO 39926 <https://bugs.python.org/issue39926>, Unicode support updated to version 13.0.0; * BPO 1635741 <https://bugs.python.org/issue1635741>, when Python is initialized multiple times in the same process, it does not leak memory anymore; * A number of Python builtins (range, tuple, set, frozenset, list, dict) are now sped up using PEP 590 <https://www.python.org/dev/peps/pep-0590> vectorcall; * A number of Python modules (_abc, audioop, _bz2, _codecs, _contextvars, _crypt, _functools, _json, _locale, operator, resource, time, _weakref) now use multiphase initialization as defined by PEP 489 <https://www.python.org/dev/peps/pep-0489/>; * A number of standard library modules (audioop, ast, grp, _hashlib, pwd, _posixsubprocess, random, select, struct, termios, zlib) are now using the stable ABI defined by PEP 384 <https://www.python.org/dev/peps/pep-0384/>.

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Pay for PR review and merging for VxWorks RTOS
by Xin, Peixing 10 Aug '20

10 Aug '20

Hi, Python developers: Anyone interested in PR review and merging for VxWorks RTOS? We can give a proper pay for that. Contact me if you have interest. Thanks, Peixing

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Re: Python Documentation, Python language improvement, and productive discussion
by David Antonini 09 Aug '20

09 Aug '20

Add my name. ________________________________ From: python-dev-request(a)python.org <python-dev-request(a)python.org> Sent: Sunday, August 9, 2020 11:00 AM To: python-dev(a)python.org <python-dev(a)python.org> Subject: Python-Dev Digest, Vol 205, Issue 17 Send Python-Dev mailing list submissions to python-dev(a)python.org To subscribe or unsubscribe via the World Wide Web, visit https://mail.python.org/mailman3/lists/python-dev.python.org/ or, via email, send a message with subject or body 'help' to python-dev-request(a)python.org You can reach the person managing the list at python-dev-owner(a)python.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Python-Dev digest..." Today's Topics: 1. Re: Python Documentation, Python language improvement, and productive discussion (Mats Wichmann) ---------------------------------------------------------------------- Date: Sun, 9 Aug 2020 09:39:32 -0600 From: Mats Wichmann <mats(a)python.org> Subject: [Python-Dev] Re: Python Documentation, Python language improvement, and productive discussion To: python-dev(a)python.org Message-ID: <421995fd-99ae-99a5-0262-33d243c93382(a)python.org> Content-Type: text/plain; charset=utf-8 On 8/5/20 10:43 AM, Dominic Davis-Foster wrote: > Hi Carol, > > I was wondering if you've been able to set up the workgroup yet? I'd certainly be interested in participating the there's an opportunity. > > > Stay safe > > Dom Indeed, I was wondering if there were any updates - I'm also interested in participating. -- mats ------------------------------ Subject: Digest Footer _______________________________________________ Python-Dev mailing list -- python-dev(a)python.org To unsubscribe send an email to python-dev-leave(a)python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ ------------------------------ End of Python-Dev Digest, Vol 205, Issue 17 *******************************************

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Summary of Python tracker Issues
by Python tracker 07 Aug '20

07 Aug '20

ACTIVITY SUMMARY (2020-07-31 - 2020-08-07) 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 7598 (+14) closed 45647 (+39) total 53245 (+53) Open issues with patches: 3098 Issues opened (34) ================== #41075: IDLE: Better support history navigation https://bugs.python.org/issue41075 reopened by terry.reedy #41453: A possible reference leak in _locale.localeconv() https://bugs.python.org/issue41453 opened by ZackerySpytz #41455: Python Devguide differs from python docs https://bugs.python.org/issue41455 opened by ypank #41458: Avoid overflow/underflow in math.prod() https://bugs.python.org/issue41458 opened by rhettinger #41459: pickle.load raises SystemError on malformed input https://bugs.python.org/issue41459 opened by Guillaume #41460: Translation Error in in Functional Programming HOWTO page https://bugs.python.org/issue41460 opened by mydairyyao #41461: test_pathlib assumes underlying filesystem permits creation wi https://bugs.python.org/issue41461 opened by Michael.Felt #41462: os.set_blocking() raises OSError on VxWorks RTOS https://bugs.python.org/issue41462 opened by pxinwr #41463: Avoid duplicating jump information from opcode.py in compile.c https://bugs.python.org/issue41463 opened by Mark.Shannon #41468: Unrecoverable server exiting https://bugs.python.org/issue41468 opened by albertpython #41470: smtplib.SMTP should reset internal 'helo' and 'ehlo' state wit https://bugs.python.org/issue41470 opened by Dadeos #41471: After installing python 3.x on Mac pip doesn't work at all https://bugs.python.org/issue41471 opened by peteje66 #41472: webbrowser uses deprecated env variables to detect desktop typ https://bugs.python.org/issue41472 opened by Trevinho #41473: test_gdb fails on AMD64 Fedora Rawhide 3.x https://bugs.python.org/issue41473 opened by vstinner #41474: Missing dependency on Include/cpython/frameobject.h https://bugs.python.org/issue41474 opened by skip.montanaro #41475: __future__.annotations set to become default in Python 4.0? https://bugs.python.org/issue41475 opened by cool-RR #41477: test_genericalias fails if ctypes is missing https://bugs.python.org/issue41477 opened by vstinner #41478: Empty representation of AssertionError https://bugs.python.org/issue41478 opened by Ilya Kamenshchikov #41482: docstring errors in ipaddress.IPv4Network https://bugs.python.org/issue41482 opened by eric.frederich #41483: Do not acquire lock in MemoryHandler.flush() if no target defi https://bugs.python.org/issue41483 opened by ankostis #41486: Add _BlocksOutputBuffer for bz2/lzma/zlib module https://bugs.python.org/issue41486 opened by malin #41487: Builtin bigint modulo operation can be made faster when the ba https://bugs.python.org/issue41487 opened by shlomif2 #41489: HTMLParser : HTMLParser.error creating multiple errors. https://bugs.python.org/issue41489 opened by AbcSxyZ #41490: Update bundled pip to 20.2.1 and setuptools to 49.2.1 https://bugs.python.org/issue41490 opened by steve.dower #41491: plistlib can't load macOS BigSur system LaunchAgent https://bugs.python.org/issue41491 opened by jckwhet #41492: Fix signing description for Windows release builds https://bugs.python.org/issue41492 opened by steve.dower #41494: Add window resizing support [ SIGWINCH ] to Lib/pty https://bugs.python.org/issue41494 opened by soumendra #41496: Create public API for typing._eval_type https://bugs.python.org/issue41496 opened by Dominik V. #41497: Potential UnicodeDecodeError in dis https://bugs.python.org/issue41497 opened by zkonge #41498: Undefinied _Py_Sigset_Converter function when HAVE_SIGSET_T no https://bugs.python.org/issue41498 opened by Roman Yurchak #41499: logging nested file path https://bugs.python.org/issue41499 opened by Norfeldt #41501: 0x80070643, can't install any version https://bugs.python.org/issue41501 opened by BSMMedia #41502: Option for Colored Logging in http.server Module https://bugs.python.org/issue41502 opened by alichtman #41503: Race between setTarget and flush in logging.handlers.MemoryHan https://bugs.python.org/issue41503 opened by iritkatriel Most recent 15 issues with no replies (15) ========================================== #41503: Race between setTarget and flush in logging.handlers.MemoryHan https://bugs.python.org/issue41503 #41502: Option for Colored Logging in http.server Module https://bugs.python.org/issue41502 #41501: 0x80070643, can't install any version https://bugs.python.org/issue41501 #41498: Undefinied _Py_Sigset_Converter function when HAVE_SIGSET_T no https://bugs.python.org/issue41498 #41496: Create public API for typing._eval_type https://bugs.python.org/issue41496 #41494: Add window resizing support [ SIGWINCH ] to Lib/pty https://bugs.python.org/issue41494 #41489: HTMLParser : HTMLParser.error creating multiple errors. https://bugs.python.org/issue41489 #41486: Add _BlocksOutputBuffer for bz2/lzma/zlib module https://bugs.python.org/issue41486 #41472: webbrowser uses deprecated env variables to detect desktop typ https://bugs.python.org/issue41472 #41470: smtplib.SMTP should reset internal 'helo' and 'ehlo' state wit https://bugs.python.org/issue41470 #41462: os.set_blocking() raises OSError on VxWorks RTOS https://bugs.python.org/issue41462 #41461: test_pathlib assumes underlying filesystem permits creation wi https://bugs.python.org/issue41461 #41460: Translation Error in in Functional Programming HOWTO page https://bugs.python.org/issue41460 #41453: A possible reference leak in _locale.localeconv() https://bugs.python.org/issue41453 #41443: some test cases in test_posix.py fail if some os attributes ar https://bugs.python.org/issue41443 Most recent 15 issues waiting for review (15) ============================================= #41503: Race between setTarget and flush in logging.handlers.MemoryHan https://bugs.python.org/issue41503 #41497: Potential UnicodeDecodeError in dis https://bugs.python.org/issue41497 #41496: Create public API for typing._eval_type https://bugs.python.org/issue41496 #41494: Add window resizing support [ SIGWINCH ] to Lib/pty https://bugs.python.org/issue41494 #41492: Fix signing description for Windows release builds https://bugs.python.org/issue41492 #41490: Update bundled pip to 20.2.1 and setuptools to 49.2.1 https://bugs.python.org/issue41490 #41486: Add _BlocksOutputBuffer for bz2/lzma/zlib module https://bugs.python.org/issue41486 #41482: docstring errors in ipaddress.IPv4Network https://bugs.python.org/issue41482 #41477: test_genericalias fails if ctypes is missing https://bugs.python.org/issue41477 #41475: __future__.annotations set to become default in Python 4.0? https://bugs.python.org/issue41475 #41474: Missing dependency on Include/cpython/frameobject.h https://bugs.python.org/issue41474 #41473: test_gdb fails on AMD64 Fedora Rawhide 3.x https://bugs.python.org/issue41473 #41472: webbrowser uses deprecated env variables to detect desktop typ https://bugs.python.org/issue41472 #41463: Avoid duplicating jump information from opcode.py in compile.c https://bugs.python.org/issue41463 #41462: os.set_blocking() raises OSError on VxWorks RTOS https://bugs.python.org/issue41462 Top 10 most discussed issues (10) ================================= #41458: Avoid overflow/underflow in math.prod() https://bugs.python.org/issue41458 20 msgs #41303: perf_counter result does not count system sleep time in Mac OS https://bugs.python.org/issue41303 18 msgs #41473: test_gdb fails on AMD64 Fedora Rawhide 3.x https://bugs.python.org/issue41473 10 msgs #38628: Issue with ctypes in AIX https://bugs.python.org/issue38628 9 msgs #38119: resource tracker destroys shared memory segments when other pr https://bugs.python.org/issue38119 7 msgs #38912: test_asyncio altered the execution environment https://bugs.python.org/issue38912 7 msgs #40275: test.support has way too many imports https://bugs.python.org/issue40275 7 msgs #41474: Missing dependency on Include/cpython/frameobject.h https://bugs.python.org/issue41474 7 msgs #41482: docstring errors in ipaddress.IPv4Network https://bugs.python.org/issue41482 7 msgs #29269: test_socket failing in solaris https://bugs.python.org/issue29269 6 msgs Issues closed (39) ================== #18876: Problems with files opened in append mode with io module https://bugs.python.org/issue18876 closed by erik.bray #26185: zipfile.ZipInfo slots can raise unexpected AttributeError https://bugs.python.org/issue26185 closed by ned.deily #40726: ast.Call end_lineno is defined and returns None https://bugs.python.org/issue40726 closed by pablogsal #40978: Document that typing.SupportsXXX protocols are runtime checkab https://bugs.python.org/issue40978 closed by gvanrossum #40979: typing module docs: keep text, add subsections https://bugs.python.org/issue40979 closed by gvanrossum #41265: lzma/bz2 module: inefficient buffer growth algorithm https://bugs.python.org/issue41265 closed by malin #41326: Build failure in blurb-it repo: "Failed building wheel for yar https://bugs.python.org/issue41326 closed by vstinner #41335: free(): invalid pointer in list_ass_item() in Python 3.7.3 https://bugs.python.org/issue41335 closed by ned.deily #41390: Errors and warnings on generate bytecode files https://bugs.python.org/issue41390 closed by gvanrossum #41419: Path.mkdir and os.mkdir don't respect setgid if its parent is https://bugs.python.org/issue41419 closed by serhiy.storchaka #41421: Random.paretovariate sometimes raises ZeroDivisionError for sm https://bugs.python.org/issue41421 closed by rhettinger #41424: [tkinter] Grammatical error in "Packer" docs https://bugs.python.org/issue41424 closed by terry.reedy #41425: [tkinter] "Coupling Widget Variables" example missing code https://bugs.python.org/issue41425 closed by terry.reedy #41431: Optimize dict_merge for copy https://bugs.python.org/issue41431 closed by inada.naoki #41440: os.cpu_count doesn't work on VxWorks RTOS https://bugs.python.org/issue41440 closed by corona10 #41445: Adding configure temporary files to gitignore https://bugs.python.org/issue41445 closed by fj92f3jj923f923 #41446: New demo, using a web api https://bugs.python.org/issue41446 closed by Mariatta #41447: Resource Tracker in Multiprocessing Shared Memory not working https://bugs.python.org/issue41447 closed by gvanrossum #41449: An article on Python 3 stdout and stderr output buffering https://bugs.python.org/issue41449 closed by gvanrossum #41451: Cannot subclass typing.Generic with __weakref__ slot in Python https://bugs.python.org/issue41451 closed by ned.deily #41452: Inefficient BufferedReader.read(-1) https://bugs.python.org/issue41452 closed by malin #41454: while loop bug on list https://bugs.python.org/issue41454 closed by eric.smith #41456: loop.run_in_executor creat thread but not destory it after the https://bugs.python.org/issue41456 closed by cielpy #41457: Implement random.shuffled https://bugs.python.org/issue41457 closed by serhiy.storchaka #41464: Increase Code Coverage for operator.py https://bugs.python.org/issue41464 closed by iritkatriel #41465: io.TextIOWrapper.errors not writable https://bugs.python.org/issue41465 closed by doerwalter #41466: Windows installer: "Add to PATH" should be checked by default https://bugs.python.org/issue41466 closed by eryksun #41467: asyncio: recv_into() must not return b'' if the socket/pipe is https://bugs.python.org/issue41467 closed by vstinner #41469: Problem with serial communication https://bugs.python.org/issue41469 closed by xtreak #41476: test_zoneinfo fails if the _lzma module is missing https://bugs.python.org/issue41476 closed by vstinner #41479: pip install== will install 0.0.0 version in stead of showing a https://bugs.python.org/issue41479 closed by steven.daprano #41480: python won't save https://bugs.python.org/issue41480 closed by leoxie0733 #41481: pip install will install version 0.0.0 if existing in stead of https://bugs.python.org/issue41481 closed by steven.daprano #41484: Overriding dictionary value under wrong key. https://bugs.python.org/issue41484 closed by ronaldoussoren #41485: Repr of complex number with signed zero does not roundtrip https://bugs.python.org/issue41485 closed by mark.dickinson #41488: Unusable type hint should not be silently ignored https://bugs.python.org/issue41488 closed by gvanrossum #41493: Refactoring dictresize to accept only new keysize https://bugs.python.org/issue41493 closed by inada.naoki #41495: SPAM https://bugs.python.org/issue41495 closed by steven.daprano #41500: InterpolationSyntaxError reading the (windows) environment wit https://bugs.python.org/issue41500 closed by ronaldoussoren

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Premature Destruction of Shared Memory
by Vinay Sharma 06 Aug '20

06 Aug '20

As suggested by Guido I am posting a potential solution to the following problem for review. Problem <https://bugs.python.org/issue38119#msg351960> A quick fix for this problem is to prevent resource tracker from handling destruction/unlinking of shared memory. A PR <https://github.com/python/cpython/pull/15989> for the same was opened by Davin (@applio), and at this moment it is the only implemented solution to fix some of the critical issues in shared memory. But, as soon as resource tracker is removed from the picture cleanup of shared memory is dependent on the user itself and this also makes Linux’s shared memory behaviour inconsistent with windows. Windows uses a reference counting mechanism to count the number of processes using a shared memory segment. When all of them are done using it, Windows simply unlinks and frees the memory allocated to the shared memory segment. On the other hand, in Linux, even after all the processes are done using the shared memory segment, the segment will continue to exist unless it is cleaned by the respective processes. Having said that, the current implementation of Linux’s shared memory is also not consistent with windows. So, I think it makes sense to go ahead with the removal of resource tracker for now until we reach a better solution. On that note, I have mentioned some of the possible solutions here <https://bugs.python.org/msg351445>. Out of these solutions I think 5 is the best. This issue and solution 5 is currently being discussed here <https://bugs.python.org/issue38119>.

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PEP 622 (Structural Pattern Matching) questions
by Mark Shannon 06 Aug '20

06 Aug '20

Hi, I have two questions about PEP 622, as it stands. 1. Is the current version the final version? 2. Is the difference in semantics between the Django example and the proposed replacement deliberate or accidental? (The difference being the change in behaviour for sequences other than list or tuple). Cheers, Mark.

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Re: Pattern matching (alternative to PEP 622)
by Eric Nieuwland 05 Aug '20

05 Aug '20

> On 4 Aug 2020, at 14:38, Koos Zevenhoven wrote: > > Hi everyone, > > [ … analysis of design goals and possible solutions, including … ] > > Point3D(x=pi, y=SIX, z=value) It suddenly struck me that Point3D(x=pi, y=SIX, z into value) would quite accurately describe what is being established here. > [ … goes on … ] > > <expression> matches <pattern> > > and that would evaluate to a boolean-like value. Yes. I’d like that as it separates functionality (pattern matching) from the control structure (match statement). > [ … ] > > Similarly, also > point matches main_diagonal_point(pos?) > should only match if x == y == z — and then bind that value to pos. > However, one might expect to be able to write the same thing inline as > point matches Point3D(pos?, pos?, pos?) > , so based on that, multiple occurrences of the same binding target should > ensure equality. > > > What about wildcards? If ? were the wildcard, that would mean that > point matches main_diagonal_point(?) > should NOT mean the same as > point matches Point3D(?,?,?) > > [ … ] Clever observations! > —Koos —eric

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Pattern matching (alternative to PEP 622)
by Koos Zevenhoven 04 Aug '20

04 Aug '20

Hi everyone, By what I'm about to write below, I've aimed at a design to meet needs resembling those that PEP 622 deals with, although with some differences, especially in emphasis. I'm not writing a full introduction here; the intended audience of this email is people somewhat familiar with PEP 622 and its discussions. This email doesn't have much structure or anything, but I hope it's sufficiently clear. Things that this design aims to address: * Check whether an object's structure matches a given pattern * Optionally extract desired values from within that structure * Learning: patterns are understandable in a logical and consistent manner * Matching can be easily tinkered with interactively * Names used in patterns behave in a clear and intuitive way for Python programmers * ... The most difficult thing is perhaps to understand what names mean: what is being bound to, and what is a value defined elsewhere and so on. For example, if a (somewhat unrealistic) pattern looks like Point3D(x=3.14, y=6, z=_) , there are four names that refer to something: `Point3D`, `x`, `y` and `z`. To understand this, it is useful to think of the pattern as corresponding to an expression, although it is not treated as quite the same in the end. (So, here x, y, z refer to internals/arguments of Point3D) The situation becomes more difficult when the values to compare with are in variables, and/or if one wishes to extract a value from the structure. Point3D(x=pi, y=SIX, z=value) Now there is no way to tell, from this, which names refer to existing objects and which should be bound to by the operation, except by guessing. Here, `value` is supposed to be a binding target. Python already has destructuring assignment (`a, b, *rest = values`), which is similar to what happens in function calls: `def func(a, b, *rest): ...`. However, compared to this, it is more useful to see patterns as working backwards compared to this. For example, the semantics of the names in lambda value: Point3D(x=pi, y=SIX, z=value) are exactly as desired. That is, when the pattern matching is interpreted as "does this object look like what this function would produce, and if so, what would be the arguments of the function in that case?". Matching the pattern would bind to `value`. So, with this, a previous understanding of function definitions already gives you a mental model for how names work in patterns *and* for what the pattern is supposed to do. In theory, the lambda expression could BE the syntax for a pattern. However, many have wished for a different syntax even for lambdas. A slightly nicer form would be to omit the keyword `lambda`, but then one would still have to repeat the names to be bound. To avoid that, we need a way to explicitly mark "not-yet-bound names": Point3D(x=pi, y=SIX, z=value?) Before going any further, how would one invoke the matching machinery? It could be <expression> matches <pattern> and that would evaluate to a boolean-like value. With this syntax, the `is_tuple` example from PEP 622 would look something like this: def is_tuple(node: Node) -> bool: if node matches Node(children=[LParen(), RParen()]): return True elif node matches Node(children=[Leaf(value="("), Node(), Leaf(value=")")]): return True return False Or something like: def is_tuple(node: Node) -> bool: if node matches tuple_pattern: return True return False Here, `tuple_pattern` would be a pattern pre-defined with a function-like syntax. Also, if there is a `tuple_pattern`, then `is_tuple` is probably not needed at all. Note that in PEP 622, is_tuple uses a match statement with three cases. So, in effect, the full tuple_pattern had been split into subpatterns. This was only possible because it was an OR pattern. In general, splitting a longer pattern into cases like that is not possible. Longer function-like patterns, on the other hand, can be expressed using more pattern functions – just like regular functions can use helper functions. Here, tuple_pattern isn't passed any arguments. It also doesn't have any parameters. However, if it did, those would be considered wildcards, as I believe we'd want both the programmer and the compiler/optimizers to explicitly see, from the match expression, which names will/would be bound. If something other than wildcard behavior is desired, that should be explicitly specified in a "pattern function call". Let's take another example pattern: pdef main_diagonal_point(pos): return Point3D(pos, pos, pos) Now, `main_diagonal_point(0)` would refer to the origin, and `point matches main_diagonal_point` would be true for every point with `x == y == z`. Similarly, also `point matches main_diagonal_point(pos?)` should only match if `x == y == z` — and then bind that value to `pos`. However, one might expect to be able to write the same thing inline as point matches Point3D(pos?, pos?, pos?) , so based on that, multiple occurrences of the same binding target should ensure equality. What about wildcards? If ? were the wildcard, that would mean that point matches main_diagonal_point(?) should NOT mean the same as point matches Point3D(?,?,?) So each occurrence of ? would have to be treated as a "new" wildcard, but when it might be passed as an argument to a sub-pattern, it will be equivalent to effectively something like `0?` (and `1?` and so on) so that the tree occurrences (in the former case) would have to be the same. This is not the only worry about using ? for wildcards. I don't find _ as wildcard really that problematic, although it is a bit more problematic here than in PEP 622. Another option would be to use `Any` as wildcard. However, that would sound like "any *type* of object is fine", although (hopefully) it is most often clear what the *type* should be, and that it is the *value* that can be anything. (And if the type is clear, no isinstance is necessary.) Then the pattern for `isinstance(obj, Class)`. Quite similarly to using a "pattern function" without arguments above, this could be `obj matches Class`. This means that matching with an instance of `type` (inside a pattern) would default to an instance check, while other `object` instances might perhaps default to `==` if nothing else is specified. Walrus patterns? While I think people probably understood PEP 622 walrus patterns quite well, I think walrus patterns harm the understanding patterns in general, because they break the mental model of going "backwards" in some sense. The walrus pattern in PEP 622 would be perfectly described by an AND pattern instead. This is because a binding target in PEP 622 is considered a "capture pattern". The django example in PEP 622 would then be match value: case [*v, label & (Promise() | str())] if v: value = tuple(v) case _: label = key.replace('_', ' ').title() However, I prefer not to think of a binding target as a "pattern", just like I don't think patterns are assignment targets. Instead, here, one might "annotate" a "not-yet-bound name" with a (sub-)pattern: *v?, label?(Promise | str) This would bind to `v` and `label` as well as check that the thing to be bound to `label` matches Promise | str. The django example could be written like this: *if* value *matches* ***v*?*, label*?*(Promise | str) *and* v: value = tuple(v) *else*: label = key.replace('_', ' ').title() However, it would be quite possible to not add this possibility now, and instead use: *if* value *matches* ***v*?*, label*?* *and* v *and* label *matches* Promise | str: value = tuple(v) *else*: label = key.replace('_', ' ').title() I think I'll stop here for now – the internal workings and dunder methods are a whole different story. I hope this was somewhat understandable. I know I didn't explicitly explain all the semantics – I tried to hit the main points and avoid distractions. If something was unclear etc., I'll be happy to answer to any questions or concerns :). —Koos

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