Mailman 3 September 2021 - Python-Dev

deprecated-removed
by Serhiy Storchaka 08 Sep '21

08 Sep '21

I always thought that the "deprecated" directive is used if the term of removing the deprecated feature is not set yet, and the "deprecated-removed" directive is used if it is set. After removing the feature both directives are replaced with the "versionchanged" directive which only specifies the version of removing, not version of deprecation. But after reading the devguide [1] I am no longer so confident. The devguide clearly describes it as specifying version at which the feature "is" removed, not "will be" removed. Maybe I always used this directive incorrectly? Or its meaning was changed with time? Or I incorrectly understand the devguide wording? Or devguide is incorrect? Before 3.8 I only seen "deprecated-removed" with future removing version. The first use "deprecated-removed" for feature which is already deleted happened in 3.8 (maybe the directive was just not updated), and there are now many uses for features removed in asyncio in 3.10. What was the initial meaning of "deprecated-removed", how it should be used now, and is the devguide correct? [1] https://devguide.python.org/documenting/?highlight=deprecated-removed#parag…

2 1

[RELEASE] Python 3.10.0rc2 is available
by Pablo Galindo Salgado 07 Sep '21

07 Sep '21

Python 3.10 is one month away, can you believe it? This snake is still trying to bite as it has been an interesting day of fighting fires, release blockers, and a bunch of late bugs but your friendly release team always delivers :) You can get this new release while is still fresh here: https://www.python.org/downloads/release/python-3100rc2/ This is the second release candidate of Python 3.10 This release, **3.10.0rc2** , is the last preview before the final release of Python 3.10.0 on 2021-10-04. Entering the release candidate phase, only reviewed code changes which are clear bug fixes are allowed between release candidates and the final release. There will be no ABI changes from this point forward in the 3.10 series and the goal is that there will be as few code changes as possible. *The next release will be the final release of Python 3.10.0, which is currently scheduled for Monday, 2021-10-04.* Call to action ⚠️⚠️⚠️⚠️⚠️⚠️⚠️ *The 3.10 branch is now accepting changes for 3.10.**1*. To maximize stability, the final release will be cut from the v3.10.0rc2 tag. If you need the release manager (me) to cherry-pick any critical fixes, mark issues as release blockers, and/or add me as a reviewer on a critical backport PR on GitHub. To see which changes are currently cherry-picked for inclusion in 3.10.0, look at the short-lived branch-v3.10.0 https://github.com/python/cpython/tree/branch-v3.10.0 on GitHub. ⚠️⚠️⚠️⚠️⚠️⚠️⚠️ *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 3.10 compatibilities during this phase. As always, report any issues to [the Python bug tracker ](https://bugs.python.org/). Please keep in mind that this is a preview release and its use is **not** recommended for production environments. And now for something completely different Maxwell's demon is a thought experiment that would hypothetically violate the second law of thermodynamics. It was proposed by the physicist James Clerk Maxwell in 1867. In the thought experiment, a demon controls a small massless door between two chambers of gas. As individual gas molecules (or atoms) approach the door, the demon quickly opens and closes the door to allow only fast-moving molecules to pass through in one direction, and only slow-moving molecules to pass through in the other. Because the kinetic temperature of a gas depends on the velocities of its constituent molecules, the demon's actions cause one chamber to warm up and the other to cool down. This would decrease the total entropy of the two gases, without applying any work, thereby violating the second law of thermodynamics. We hope you enjoy those new releases! Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organization contributions to the Python Software Foundation. Regards from a plane going to Malaga, Your friendly release team, Pablo Galindo @pablogsal Ned Deily @nad Steve Dower @steve.dower

1 0

Making code object APIs unstable
by Guido van Rossum 07 Sep '21

07 Sep '21

In 3.11 we're changing a lot of details about code objects. Part of this is the "Faster CPython" work, part of it is other things (e.g. PEP 657 -- Fine Grained Error Locations in Tracebacks). As a result, the set of fields of the code object is changing. This is fine, the structure is part of the internal API anyway. But there's a problem with two public API functions, PyCode_New() and PyCode_NewWithPosArgs(). As we have them in the main (3.11) branch, their signatures are incompatible with previous versions, and they have to be since the set of values needed to create a code object is different. (The types.CodeType constructor signature is also changed, and so is its replace() method, but these aren't part of any stable API). Unfortunately, PyCode_New() and PyCode_NewWithPosArgs() are part of the PEP 387 stable ABI. What should we do? A. We could deprecate them, keep (restore) their old signatures, and create crippled code objects (no exception table, no endline/column tables, qualname defaults to name). B. We could deprecate them, restore the old signatures, and always raise an error when they are called. C. We could just delete them. D. We could keep them, with modified signatures, and to heck with ABI compatibility for these two. E. We could get rid of PyCode_NewWithPosArgs(), update PyCode() to add the posonlyargcount (which is the only difference between the two), and d*mn the torpedoes. F. Like (E), but keep PyCode_NewWithPosArgs() as an alias for PyCode_New() (and deprecate it). If these weren't part of the stable ABI, I'd choose (E). But because they are, I think only (A) or (B) are our options. The problem with (C) is that if there's code that links to them but doesn't call them (except in some corner case that the user can avoid), the code won't link even though it would work fine. The problem with (D) is that if it *is* called by code expecting the old signature it will segfault. I'm not keen on (A) since it can cause broken code objects when used to copy a code object with some modified metadata (e.g. a different filename), since there's no way to pass the exception table (and several other fields, but the exception table is an integral part of the code now). Code wanting to make slight modifications to code objects such as changing co_name or co_filename should switch to the .replace() API, which is much better at this (though calling it from C is a pain, it's possible). Code wanting to synthesize code should be updated for each release; we should probably require such code to be built with the internal API and use _PyCode_New(), which takes a struct argument containing all the necessary fields. Thoughts? I'm especially interested in Petr's opinion given that this is a case where we'd like to deprecate something in the stable ABI. See also discussion in https://bugs.python.org/issue40222 (esp. near the end). -- --Guido van Rossum (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-…>

16 36

[RELEASE] Python 3.7.12 and 3.6.15 security updates now available
by nad＠python.org 06 Sep '21

06 Sep '21

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

2 1

Fixing sys.platlibdir usages in sysconfig on Python 3.10
by Tzu-ping Chung 05 Sep '21

05 Sep '21

Hi I’d like to raise awareness to the two b.p.o. entries I recently created and their corresponding PRs: sysconfig's posix_user scheme has different platlib value to distutils's unix_user https://bugs.python.org/issue44860 sysconfig's posix_home scheme has different platlib value to distutils's unix_home https://bugs.python.org/issue45035 Since Python 3.10 switches from distutils to sysconfig as the canonical location to discover/install packages, I’d very much want these two to be included in 3.10.0 (and backported to 3.9 for consistency). Otherwise Python distributions that sets sys.platlibdir to a non-default value (e.g. Red Hat distributions sets it to lib64) will not be able to correctly run pip 21.3 (due October) on Python 3.10. TP -- Tzu-ping Chung (@uranusjr) uranusjr(a)gmail.com https://uranusjr.com

1 0

API's to interface python with Eclipse to execute and debug C/C++ Source files.
by Chandrakant Shrimantrao 04 Sep '21

04 Sep '21

Hi, We would like to know if there is any option available to execute and debug( setting break point and delete break point) C/C++ Source files Python API's inside Eclipse IDE after interfacing Pydev with Eclipse. Please let us know. Thanks and regards. Chandrakant shrimantrao. L&T Technology Services Ltd www.LTTS.com L&T Technology Services Limited (LTTS) is committed to safeguard your data privacy. For more information to view our commitment towards data privacy under GDPR, please visit the privacy policy on our website www.Ltts.com. This Email may contain confidential or privileged information for the intended recipient (s). If you are not the intended recipient, please do not use or disseminate the information, notify the sender and delete it from your system.

3 2

Summary of Python tracker Issues
by Python tracker 03 Sep '21

03 Sep '21

ACTIVITY SUMMARY (2021-08-27 - 2021-09-03) 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 7409 ( -4) closed 49419 (+67) total 56828 (+63) Open issues with patches: 2945 Issues opened (38) ================== #20658: os.environ.clear() fails with empty keys (posix.unsetenv) https://bugs.python.org/issue20658 reopened by iritkatriel #37330: open(): remove 'U' mode, deprecated since Python 3.3 https://bugs.python.org/issue37330 reopened by vstinner #45033: Calls to PyErr_PrintEx in destructors cause calling async func https://bugs.python.org/issue45033 opened by zbentley #45034: Improve struct.pack out of range error messages https://bugs.python.org/issue45034 opened by steven.daprano #45035: sysconfig's posix_home scheme has different platlib value to d https://bugs.python.org/issue45035 opened by uranusjr #45036: turtle.onrelease() event doesn't get triggered sometimes https://bugs.python.org/issue45036 opened by techn010je11y #45040: [sqlite3] optimise transaction control functions https://bugs.python.org/issue45040 opened by erlendaasland #45041: [sqlite3] simplify executescript() https://bugs.python.org/issue45041 opened by erlendaasland #45042: Many multiprocessing tests are silently skipped since 3.9 https://bugs.python.org/issue45042 opened by serhiy.storchaka #45046: Add support of context managers in unittest https://bugs.python.org/issue45046 opened by serhiy.storchaka #45052: WithProcessesTestSharedMemory.test_shared_memory_basics fails https://bugs.python.org/issue45052 opened by sobolevn #45053: MD5SumTests.test_checksum_fodder fails on Windows https://bugs.python.org/issue45053 opened by sobolevn #45054: json module should issue warning about duplicate keys https://bugs.python.org/issue45054 opened by Zeturic #45055: Fresh build on Windows fails the first time for zlib.c https://bugs.python.org/issue45055 opened by gvanrossum #45056: compiler: Unnecessary None in co_consts https://bugs.python.org/issue45056 opened by methane #45058: Undefined behavior for syntax "except AError or BError:" accep https://bugs.python.org/issue45058 opened by kftse20031207 #45060: Do not use the equality operators with None https://bugs.python.org/issue45060 opened by serhiy.storchaka #45062: test_asyncio: test_huge_content_recvinto() failed on PPC64LE R https://bugs.python.org/issue45062 opened by vstinner #45063: PEP 657 Fine Grained Error Locations: omit indicators if they https://bugs.python.org/issue45063 opened by vstinner #45065: test_asyncio failed (env changed) on s390x RHEL8 Refleaks 3.10 https://bugs.python.org/issue45065 opened by vstinner #45066: email parser fails to decode quoted-printable rfc822 message a https://bugs.python.org/issue45066 opened by anarcat #45067: Failed to build _curses on CentOS 7 https://bugs.python.org/issue45067 opened by orsenthil #45069: python 3.9.2 contains libcrypto-1_1.dll and libssl-1_1.dll ass https://bugs.python.org/issue45069 opened by xcl123 #45073: windows installer quiet installation targetdir escapes "quote" https://bugs.python.org/issue45073 opened by DMI-1407 #45074: asyncio hang in subprocess wait_closed() on Windows, BrokenPip https://bugs.python.org/issue45074 opened by byllyfish #45075: confusion between frame and frame_summary in traceback module https://bugs.python.org/issue45075 opened by iritkatriel #45077: multiprocessing.Pool(64) crashes on Windows https://bugs.python.org/issue45077 opened by saschanaz #45078: test_importlib: test_read_bytes() fails on AMD64 Windows8.1 No https://bugs.python.org/issue45078 opened by vstinner #45083: Need to use the exception class qualname when rendering except https://bugs.python.org/issue45083 opened by iritkatriel #45084: urllib.parse: remove deprecated functions (splittype, to_bytes https://bugs.python.org/issue45084 opened by vstinner #45086: f-string unmatched ']' https://bugs.python.org/issue45086 opened by Greg Kuhn #45088: Coroutines & async generators disagree on the iteration protoc https://bugs.python.org/issue45088 opened by yselivanov #45089: [sqlite3] the trace callback does not raise exceptions on erro https://bugs.python.org/issue45089 opened by erlendaasland #45090: Add pairwise to What's New in Python 3.10; mark it as new in i https://bugs.python.org/issue45090 opened by ramalho #45091: inspect.Parameter.__str__ does not include subscripted types i https://bugs.python.org/issue45091 opened by antonio-caceres #45093: Add method to compare dicts accounting for order https://bugs.python.org/issue45093 opened by mcarans #45094: Consider using __forceinline and __attribute__((always_inline) https://bugs.python.org/issue45094 opened by vstinner #45095: Easier loggers traversal tree with a logger.getChildren method https://bugs.python.org/issue45095 opened by sblondon Most recent 15 issues with no replies (15) ========================================== #45095: Easier loggers traversal tree with a logger.getChildren method https://bugs.python.org/issue45095 #45091: inspect.Parameter.__str__ does not include subscripted types i https://bugs.python.org/issue45091 #45090: Add pairwise to What's New in Python 3.10; mark it as new in i https://bugs.python.org/issue45090 #45089: [sqlite3] the trace callback does not raise exceptions on erro https://bugs.python.org/issue45089 #45088: Coroutines & async generators disagree on the iteration protoc https://bugs.python.org/issue45088 #45084: urllib.parse: remove deprecated functions (splittype, to_bytes https://bugs.python.org/issue45084 #45074: asyncio hang in subprocess wait_closed() on Windows, BrokenPip https://bugs.python.org/issue45074 #45062: test_asyncio: test_huge_content_recvinto() failed on PPC64LE R https://bugs.python.org/issue45062 #45046: Add support of context managers in unittest https://bugs.python.org/issue45046 #45040: [sqlite3] optimise transaction control functions https://bugs.python.org/issue45040 #45035: sysconfig's posix_home scheme has different platlib value to d https://bugs.python.org/issue45035 #45034: Improve struct.pack out of range error messages https://bugs.python.org/issue45034 #45033: Calls to PyErr_PrintEx in destructors cause calling async func https://bugs.python.org/issue45033 #45030: Integer overflow in __reduce__ of the range iterator https://bugs.python.org/issue45030 #45023: Python doesn't exit with proper resultcode on SIGINT in multip https://bugs.python.org/issue45023 Most recent 15 issues waiting for review (15) ============================================= #45094: Consider using __forceinline and __attribute__((always_inline) https://bugs.python.org/issue45094 #45089: [sqlite3] the trace callback does not raise exceptions on erro https://bugs.python.org/issue45089 #45084: urllib.parse: remove deprecated functions (splittype, to_bytes https://bugs.python.org/issue45084 #45083: Need to use the exception class qualname when rendering except https://bugs.python.org/issue45083 #45078: test_importlib: test_read_bytes() fails on AMD64 Windows8.1 No https://bugs.python.org/issue45078 #45075: confusion between frame and frame_summary in traceback module https://bugs.python.org/issue45075 #45060: Do not use the equality operators with None https://bugs.python.org/issue45060 #45056: compiler: Unnecessary None in co_consts https://bugs.python.org/issue45056 #45046: Add support of context managers in unittest https://bugs.python.org/issue45046 #45042: Many multiprocessing tests are silently skipped since 3.9 https://bugs.python.org/issue45042 #45041: [sqlite3] simplify executescript() https://bugs.python.org/issue45041 #45040: [sqlite3] optimise transaction control functions https://bugs.python.org/issue45040 #45035: sysconfig's posix_home scheme has different platlib value to d https://bugs.python.org/issue45035 #45030: Integer overflow in __reduce__ of the range iterator https://bugs.python.org/issue45030 #45027: Allow basicConfig to configure any logger, not just root https://bugs.python.org/issue45027 Top 10 most discussed issues (10) ================================= #45020: Freeze all modules imported during startup. https://bugs.python.org/issue45020 27 msgs #36521: Consider removing docstrings from co_consts in code objects https://bugs.python.org/issue36521 15 msgs #44689: ctypes.util.find_library() does not find macOS 11+ system libr https://bugs.python.org/issue44689 13 msgs #27175: Unpickling Path objects https://bugs.python.org/issue27175 11 msgs #44895: refleak test failure in test_exceptions https://bugs.python.org/issue44895 10 msgs #25130: Make tests more PyPy compatible https://bugs.python.org/issue25130 9 msgs #45025: Reliance on C bit fields in C API is undefined behavior https://bugs.python.org/issue45025 8 msgs #45042: Many multiprocessing tests are silently skipped since 3.9 https://bugs.python.org/issue45042 8 msgs #34561: Replace list sorting merge_collapse()? https://bugs.python.org/issue34561 7 msgs #37596: Reproducible pyc: frozenset is not serialized in a determinist https://bugs.python.org/issue37596 7 msgs Issues closed (62) ================== #16379: SQLite error code not exposed to python https://bugs.python.org/issue16379 closed by erlendaasland #19027: undefined symbol: _PyParser_Grammar https://bugs.python.org/issue19027 closed by iritkatriel #27334: [sqlite3] context manager leaves db locked if commit fails in https://bugs.python.org/issue27334 closed by erlendaasland #31962: test_importlib double free or corruption https://bugs.python.org/issue31962 closed by vstinner #32766: 4.7.7. Function Annotations https://bugs.python.org/issue32766 closed by iritkatriel #33511: Update config.sub https://bugs.python.org/issue33511 closed by iritkatriel #35391: threading.RLock exception handling while waiting https://bugs.python.org/issue35391 closed by pitrou #37694: Crash when calling zipimport.zipimporter.__new__().<method>() https://bugs.python.org/issue37694 closed by iritkatriel #37719: addSubtest not calling addFailure and addError https://bugs.python.org/issue37719 closed by serhiy.storchaka #39218: Assertion failure when calling statistics.variance() on a floa https://bugs.python.org/issue39218 closed by rhettinger #39241: Popen of python3.6 hangs on os.read(errpipe_read, 50000) https://bugs.python.org/issue39241 closed by iritkatriel #39320: Handle unpacking of */** arguments and rvalues in the compiler https://bugs.python.org/issue39320 closed by Mark.Shannon #39817: CRITICAL: TypeError: cannot pickle 'generator' https://bugs.python.org/issue39817 closed by iritkatriel #40360: Deprecate lib2to3 (and 2to3) for future removal https://bugs.python.org/issue40360 closed by vstinner #40935: Links to Python3 docs for some libs return 404 https://bugs.python.org/issue40935 closed by ned.deily #41620: Python Unittest does not return results object when the test i https://bugs.python.org/issue41620 closed by lukasz.langa #42255: webbrowser.MacOSX is unused, untested and undocumented https://bugs.python.org/issue42255 closed by lukasz.langa #43124: [security] smtplib multiple CRLF injection https://bugs.python.org/issue43124 closed by lukasz.langa #43612: zlib.compress should have a wbits argument https://bugs.python.org/issue43612 closed by lukasz.langa #43613: gzip.compress and gzip.decompress are sub-optimally implemente https://bugs.python.org/issue43613 closed by rhpvorderman #43913: unittest module cleanup functions not run unless tearDownModul https://bugs.python.org/issue43913 closed by lukasz.langa #44135: issubclass documentation doesn't explain tuple semantic https://bugs.python.org/issue44135 closed by lukasz.langa #44394: [security] CVE-2013-0340 "Billion Laughs" fixed in Expat >=2.4 https://bugs.python.org/issue44394 closed by ned.deily #44449: Segfault in _PyTrash_begin when faulthandler tries to dump thr https://bugs.python.org/issue44449 closed by vstinner #44489: _handle_existing_loggers should respect loggers that were manu https://bugs.python.org/issue44489 closed by vinay.sajip #44925: [docs] Confusing deprecation notice for typing.IO https://bugs.python.org/issue44925 closed by lukasz.langa #44962: asyncio.create_task weakrefset race condition https://bugs.python.org/issue44962 closed by lukasz.langa #44980: Clean up tests that return a value that isn't None https://bugs.python.org/issue44980 closed by andrei.avk #45001: Date parsing helpers in email module incorrectly raise IndexEr https://bugs.python.org/issue45001 closed by ned.deily #45007: OpenSSL 1.1.1l is released https://bugs.python.org/issue45007 closed by lukasz.langa #45018: Pickling a range iterator with an index of over sizeof(int) st https://bugs.python.org/issue45018 closed by lukasz.langa #45019: Freezing modules has manual steps but could be automated. https://bugs.python.org/issue45019 closed by eric.snow #45029: tkinter doc, hello world example - quit button clobbers method https://bugs.python.org/issue45029 closed by terry.reedy #45031: [Windows] datetime.fromtimestamp(t) when t = 253402210800 fail https://bugs.python.org/issue45031 closed by eryksun #45032: struct.unpack() returns NaN https://bugs.python.org/issue45032 closed by steven.daprano #45037: theme-change.py for tkinter lib https://bugs.python.org/issue45037 closed by zach.ware #45038: Bugs https://bugs.python.org/issue45038 closed by zach.ware #45039: use ADDOP_LOAD_CONST consistently https://bugs.python.org/issue45039 closed by iritkatriel #45043: Typo (change 'two' to 'three') https://bugs.python.org/issue45043 closed by nofliesonyou #45044: Agreeing on error raised by large repeat value for sequences https://bugs.python.org/issue45044 closed by rhettinger #45045: Optimize mapping patterns of structural pattern matching https://bugs.python.org/issue45045 closed by corona10 #45047: Update demo files https://bugs.python.org/issue45047 closed by serhiy.storchaka #45048: subprocess.run(capture_output=Bool) does the opposite of expec https://bugs.python.org/issue45048 closed by DragonEggBedrockBreaking #45049: added cbrt() in MATH_RADIANS_METHODDEF which is missing befor https://bugs.python.org/issue45049 closed by serhiy.storchaka #45050: created unittest file analyze_text.py https://bugs.python.org/issue45050 closed by serhiy.storchaka #45051: wrote optimised async_test.py for async lib https://bugs.python.org/issue45051 closed by zach.ware #45057: Simplify RegressionTestResult https://bugs.python.org/issue45057 closed by serhiy.storchaka #45059: Typo: using "==" instead of "=" https://bugs.python.org/issue45059 closed by terry.reedy #45061: [C API] Detect refcount bugs on True/False in C extensions https://bugs.python.org/issue45061 closed by vstinner #45064: Raising AttributeError in descriptor decorator causing searchi https://bugs.python.org/issue45064 closed by uriyyo #45068: python 3.9.2 contains libcrypto-1_1.dll and libssl-1_1.dll ass https://bugs.python.org/issue45068 closed by zach.ware #45070: python 3.9.2 contains wininst-10.0-amd64.exe. wininst-10.0.exe https://bugs.python.org/issue45070 closed by zach.ware #45071: python 3.9.2 contains _bz2.pyd associates CVE-2019-12900 and C https://bugs.python.org/issue45071 closed by zach.ware #45072: python 3.9.2 contains ensurepip and pip associates CVE-2021-35 https://bugs.python.org/issue45072 closed by zach.ware #45076: open "r+" problem https://bugs.python.org/issue45076 closed by zach.ware #45079: 3.8.11 and 3.8.12 missing Windows artifacts, only tarballs - b https://bugs.python.org/issue45079 closed by zach.ware #45080: functools._HashedSeq implements __hash__ but not __eq__ https://bugs.python.org/issue45080 closed by leopold.talirz #45081: dataclasses that inherit from Protocol subclasses have wrong _ https://bugs.python.org/issue45081 closed by julianfortune #45082: ctypes: Deprecate c_buffer() alias to create_string_buffer() https://bugs.python.org/issue45082 closed by lukasz.langa #45085: Remove the binhex module, binhex4 and hexbin4 standards https://bugs.python.org/issue45085 closed by lukasz.langa #45087: Confusing error message when trying split bytes. https://bugs.python.org/issue45087 closed by eric.smith #45092: Make set ordered like dict https://bugs.python.org/issue45092 closed by serhiy.storchaka

1 0

Is anyone relying on new-bugs-announce/python-bugs-list/bugs.python.org summaries
by Ammar Askar 03 Sep '21

03 Sep '21

Hey everyone, As part of PEP 588, migrating bugs.python.org issues to Github, there are two current mailing list related items that need a replacement or need to be turned down. 1. Weekly summary emails with bug counts and issues from the week, example: https://mail.python.org/archives/list/python-dev@python.org/thread/JRFJ4QH7… 2. Emails sent to the new-bugs-announce and python-bugs-list for new issues and comments to existing issues. I wanted to quickly gauge if anyone is relying on these mailing lists/emails or if it's a convenient part of your workflow. Feel free to chime in here or on the migration issues directly with your use-case: 1. https://github.com/psf/gh-migration/issues/6 2. https://github.com/psf/gh-migration/issues/7 Thanks, Ammar

7 6

PEP-535 (Rich comparison chaining) Discussion?
by Angus Hollands 02 Sep '21

02 Sep '21

Hi all, PEP 535 was deferred until Python 3.8. I would like to discuss the PEP given that some time has passed, and I _personally_ would benefit from its acceptance. ## A little about me: As a reasonably long-time Python user (well, 16 years), I have gradually moved from using only the core language to working within the DSLs (NumPy et al.) of the Scientific Python ecosystem. Most recently, I've been using Awkward Arrray (https://github.com/scikit-hep/awkward-1.0), which generalises the regular NumPy array programming paradigm into "jagged" data structures, and was initially aimed at the High Energy Physics (HEP) domain. ## TL;DR of the PEP's Motivations: Various aspects of NumPy's API have become a "lingua-franca" in the Scientific Python domain, such as strongly-overloaded index operations. One such overload allows "mask arrays" — arrays with boolean entries corresponding to a per-element mask — to select a subset of the array. These mask arrays are conveniently built from the rich comparison operators that Python supports, e.g. ```python x = np.array(...) y = x[(2 < x) & (x < 8)] ``` As discussed in PEP 535, the limitation on comparison chaining (namely that it is not possible for rich comparisons) makes the above syntax more clunky than it might otherwise be. The main repercussion of this limitation is lower readability: - operator precedence of bitwise and/or requires a reasonable number of parentheses (https://docs.python.org/3/reference/expressions.html#operator-precedence) - repetition of the rich-object (array) With PEP 535 (and the necessary library changes), this would look more like ```python x = np.array(...) y = x[2 < x < 8] ``` This is already well described in the PEP, so I'll leave the example there! ## Community Survey The Oct 2020 Python Developers Survey (https://www.jetbrains.com/lp/python-developers-survey-2020/) suggests that 62% of respondents use NumPy. Additionally, 37% of respondents list "Simple syntax, syntactic sugar, easy to learn" and 30% list "Easy to write & read code, high-level language" amongst their three most liked features in the Python language (to clarify, these answers may overlap by respondent!) From these results, I would make a tentative case that this PEP would have a reasonable impact on the Python community, given that libraries benefitting from this proposal (e.g. NumPy) are used by a "majority" of those surveyed. ## Conclusion This is a bit of a long opener to this list (apologies!). Is there any interest in pushing this PEP along? Thanks, Angus Hollands

4 4