Mailman 3 January 2021 - Python-Dev

Re: 3.10 change (?) for __bool__
by Mark Shannon 13 Jan '21

13 Jan '21

Hi Rob, On 13/01/2021 12:18 pm, Rob Cliffe wrote: > > > On 12/01/2021 15:53, Mark Shannon wrote: >> >> In master we convert `if x: pass` to `pass` which is equivalent, >> unless bool(x) has side effects the first time it is called. This is a >> recent change. > Can you please confirm that this optimisation ONLY applies to bare > names, i.e. NOT > > if x(): pass > if x.y: pass > if x+y: pass The optimization doesn't apply to the expression, but the test. The optimizer (might) transform if x+y: pass to x+y But the expression is still evaluated. Sorry for the confusion, I should have been clearer in my example. It is the call to `bool()` that *might* be eliminated. Cheers, Mark. > > Thanks > Rob Cliffe

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Heap types (PyType_FromSpec) must fully implement the GC protocol
by Victor Stinner 12 Jan '21

12 Jan '21

Hi, In the Python stdlib, many heap types currently don't "properly" (fully?) implement the GC protocol which can prevent to destroy these types at Python exit. As a side effect, some other Python objects can also remain alive, and so are not destroyed neither. There is an on-going effect to destroy all Python objects at exit (bpo-1635741). This problem is getting worse when subinterpreters are involved: Refleaks buildbots failures which prevent to spot other regressions, and so these "leaks" / "GC bugs" must be fixed as soon as possible. In my experience, many leaks spotted by tests using subinterpreters were quite old, it's just that they were ignored previously. It's an hard problem and I don't see any simple/obvious solution right now, except of *workarounds* that I dislike. Maybe the only good solution is to fix all heap types, one by one. == Only the Python stdlib should be affected == PyType_FromSpec() was added to Python 3.2 by the PEP 384 to define "heap types" in C, but I'm not sure if it's popular in practice (ex: Cython doesn't use it, but defines static types). I expect that most types to still be defined the old style (static types) in a vas majority of third party extension modules. To be clear, static types are not affected by this email. Third party extension modules using the limited C API (to use the stable ABI) and PyType_FromSpec() can be affected (if they don't fully implement the GC protocol). == Heap type instances now stores a strong reference to their type == In March 2019, the PyObject_Init() function was modified in bpo-35810 to keep a strong reference (INCREF) to the type if the type is a heap type. The fixed problem was that heap types could be destroyed before the last instance is destroyed. == GC and heap types == The new problem is that most heap types don't collaborate well with the garbage collector. The garbage collector doesn't know anything about Python objects, types, reference counting or anything. It only uses the PyGC_Head header and the traverse functions. If an object holds a strong reference to an object but its type does not define a traverse function, the GC cannot guess/infer this reference. A heap type must respect the following 3 conditions to collaborate with the GC: * Have the Py_TPFLAGS_HAVE_GC flag; * Define a traverse function (tp_traverse) which visits the type: Py_VISIT(Py_TYPE(self)); * Instances must be tracked by the GC. If one of these conditions is not met, the GC can fail to destroy a type during a GC collection. If an instance is kept alive late while a Python interpreter is being deleted, it's possible that the type is never deleted, which can keep indirectly *many* objects alive and so don't delete them neither. In practice, when a type is not deleted, a test using subinterpreter starts to fail on Refleaks buildbot since it leaks references. Without subinterpreters, such leak is simply ignored, whereas this is an on-going effect to delete Python objects at exit (bpo-1635741). == Boring traverse functions == Currently, there is no default traverse implementation which visits the type. For example, I had the implement the following function for _thread.LockType: static int lock_traverse(lockobject *self, visitproc visit, void *arg) { Py_VISIT(Py_TYPE(self)); return 0; } It's a little bit annoying to have to implement the GC protocol whereas a lock cannot contain other Python objects, it's not a container. It's just a thin wrapper to a C lock. There is exactly one strong reference: to the type. == Workaround: loop on gc.collect() == A workaround is to run gc.collect() in a loop until it returns 0 (no object was collected). == Traverse automatically? Nope. == Pablo Galindo attempts to automatically visit the type in the traverse function: https://bugs.python.org/issue40217 https://github.com/python/cpython/commit/0169d3003be3d072751dd14a5c84748ab6… Moreover, What's New in Python 3.9 contains a long section suggesting to implement a traverse function for this problem, but it doesn't suggest to track instances: https://docs.python.org/dev/whatsnew/3.9.html#changes-in-the-c-api This solution causes too many troubles, and so instead, traverse functions were defined on heap types to visit the type. Currently in the master branch, 89 types are defined as heap types on a total of 206 types (117 types are defined statically). I don't think that these 89 heap types respect the 3 conditions to collaborate with the GC. == How should we address this issue? == I'm not sure what should be done. Working around the issue by triggering multiple GC collections? Emit a warning in development mode if a heap type doesn't collaborate well with the GC? If core developers miss these bugs and have troubles to debug them, I expect that extension module authors would suffer even more. == GC+heap type bugs became common == I'm fixing such GC issue for 1 year as part as the work on cleaning Python objects at exit, and also indirectly related to subinterpreters. The behavior is surprising, it's really hard to dig into GC internals and understand what's going on. I wrote an article on this kind of "GC bugs": https://vstinner.github.io/subinterpreter-leaks.html Today, I learnt the hard way that defining a traverse is *not* enough. The type constructor (tp_new) must also track instances! See my fix for _multibytecodec related to CJK codecs: https://github.com/python/cpython/commit/11ef53aefbecfac18b63cee518a7184f77… https://bugs.python.org/issue42866 == Reference cycles are common == The GC only serves to break reference cycles. But reference cycles are rare, right? Well... First of all, most types create reference cycles involing themselves. For example, a type __mro__ tuple contains the type which already creates a ref cycle. Type methods can also contain a reference to the type. => The GC must break the cycle, otherwise the type cannot be destroyed When a function is defined in a Python module, the function __globals__ is the module namespace (module.__dict__) which... contains the function. Defining a function in a Python module also creates a reference cycle which prevents to delete the module namespace. If a function is used as a callback somewhere, the whole module remains "alive" until the reference to the callback is cleared. Example. os.register_at_fork() and codecs.register() callbacks are cleared really late during Python finalization. Currently, it's basically the last objects which are cleared at Python exit. After that, there is exactly one final GC collection. => The GC == Debug GC issues == * gc.get_referents() and gc.get_referrers() can be used to check traverse functions. * gc.is_tracked() can be used to check if the GC tracks an object. * Using the gdb debugger on gc_collect_main() helps to see which objects are collected. See for example the finalize_garbage() functions which calls finalizers on unreachable objects. * The solution is usually a missing traverse functions or a missing Py_VISIT() in an existing traverse function. == __del__ hack for debugging == If you want to play with the issue or if you have to debug a GC issue, you can use an object which logs a message when it's being deleted: class VerboseDel: def __del__(self): print("DELETE OBJECT") obj = VerboseDel() Warning: creating such object in a module also prevents to destroy the module namespace when the last reference to the module is deleted! __del__.__globals__ contains a reference to the module namespace, and obj.__class__ contains a reference to the type... Yeah, ref cycle and GC issues are fun! == Long email == Yeah, I like to put titles in my long emails. Enjoy. Happy hacking! Victor -- Night gathers, and now my watch begins. It shall not end until my death.

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why include cpython/*.h, Need this macro ? # error "this header file must not be included directly"
by junyixie 11 Jan '21

11 Jan '21

#ifndef Py_LIMITED_API # define Py_CPYTHON_FILEOBJECT_H # include "cpython/fileobject.h" # undef Py_CPYTHON_FILEOBJECT_H #endif cpython/fileobject.h ``` #ifndef Py_CPYTHON_FILEOBJECT_H # error "this header file must not be included directly" #endif ``` why not use #ifndef #define cpython/fileobject.h #ifndef Py_CPYTHON_FILEOBJECT_H #define Py_CPYTHON_FILEOBJECT_H .... #endif /* Py_CPYTHON_FILEOBJECT_H */

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PEP 642 v3: Explicit patterns for structured pattern matching
by Nick Coghlan 11 Jan '21

11 Jan '21

I’ve made a final round of updates to PEP 642 and submitted it to the Steering Council for consideration alongside PEP 634. As usual, the rendered version can be found here: https://www.python.org/dev/peps/pep-0642/ There's a Discourse thread at https://discuss.python.org/t/pep-642-v3-explicit-pattern-syntax-for-structu…, and the rest of the email covers the same points as the opening post in that thread. There are some pretty significant changes relative to v2, although I did already discuss most of them in the v2 thread at https://discuss.python.org/t/pep-642-constraint-pattern-syntax-for-structur… The PEP itself contains a list of major changes relative to PEP 634, so I won’t repeat that here: https://www.python.org/dev/peps/pep-0642/#appendix-c-summary-of-changes-rel… Instead I’ll summarise the parts that I consider most important: * ensuring that all “binding to the right” operations use the as keyword. This drove changes to both mapping patterns and class patterns. * explicitly qualifying both name bindings and value constraints with `as`, `==`, or `is`. This change makes it possible to make pattern matching available to users without having to resolve the thorny questions of what bare names and attribute references should do by default. It also opens up the possibility of potentially adding more value constraint options later (like `in` , `is not`, and `!=`) if those operations seem sufficiently compelling to be worth adding. * explicitly decoupling sequence pattern matching from iterable unpacking. The change to require qualification of name binding operations already breaks the alignment between the two, and that created an opportunity to simplify the grammar by only allowing square bracket based sequence patterns and eliminating both open sequence patterns and parenthesis based sequence patterns * changing class patterns to draw more of their syntactic inspiration from mapping patterns rather than from class instantiation * explicitly representing patterns in the AST, rather than treating patterns as pseudo-expressions all the way through to the code generation layer. Skipping this step makes the code fragile and hard to follow, as there isn’t actually any point in the AST that accepts both expressions and patterns, but with pattern parsing reusing expression nodes, you can’t tell from just looking at the AST which nodes expect subexpressions and which expect subpatterns. I’ll also quote the example match statement from the PEP abstract, which extracts “host” and “port” details from a 2 item sequence, a mapping with “host” and “port” keys, any object with “host” and “port” attributes, or a “host:port” string, treating the “port” as optional in the latter three cases: port = DEFAULT_PORT match expr: case [as host, as port]: pass case {"host" as host, "port" as port}: pass case {"host" as host}: pass case object{.host as host, .port as port}: pass case object{.host as host}: pass case str{} as addr: host, __, optional_port = addr.partition(":") if optional_port: port = optional_port case __ as m: raise TypeError(f"Unknown address format: {m!r:.200}") port = int(port) Cheers, Nick. -- Nick Coghlan | ncoghlan(a)gmail.com | Brisbane, Australia

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Extending python's graphlib module
by Touqir Sajed 10 Jan '21

10 Jan '21

It was really good to see Python 3.9 adding the topological sort algorithm. What other algorithms might come next to the graphlib module? I think the basic ones like BFS, DFS, Bellman Ford's shortest path algorithm will be quite useful to have. Let me know if contributions are welcome. Thanks!

1 0

unittest of sequence equality
by Alan G. Isaac 10 Jan '21

10 Jan '21

The following test fails because because `seq1 == seq2` returns a (boolean) NumPy array whenever either seq is a NumPy array. import unittest import numpy as np unittest.TestCase().assertSequenceEqual([1.,2.,3.], np.array([1.,2.,3.])) I expected `unittest` to rely only on features of a `collections.abc.Sequence`, which based on https://docs.python.org/3/glossary.html#term-sequence, I believe are satisfied by a NumPy array. Specifically, I see no requirement that a sequence implement __eq__ at all much less in any particular way. In short: a test named `assertSequenceEqual` should, I would think, work for any sequence and therefore (based on the available documentation) should not depend on the class-specific implementation of __eq__. Is that wrong? Thank you, Alan Isaac

10 16

Story behind vars() vs .__dict__
by Paul Sokolovsky 08 Jan '21

08 Jan '21

Hello, I would easily bet 10 bucks that vars() is the least known, and least used, of the Python builtin functions. My mental model of it was: it was introduced (perhaps in Python3) to "harmonize" all the existing .__dict__ stuff, and provide more abstract interface for it, with .__dict__ patiently waiting its deprecation in CPython 10 or something. Was I wrong with thinking like that, and finding that vars() was already in the docs of CPython 1.4, the earliest doc version hosted at python.org: https://docs.python.org/release/1.4/lib/node26.html#SECTION0033000000000000… So it seems it was around "always", but then the question is why both vars() and .__dict__ are round for so long, and there was no (successful) attempt to stop breaking object encapsulation e.g. on transitioning to Python3000? Anybody has any references to the story of them? I can't find anything relevant so far. I in particular made sure to google for "vars site:python-history.blogspot.com" with 0 hits. Expected clarification on ".__dict__ breaking object encapsulation": Usually, object attributes are used to access "some small piece of data" "stored inside" an object. .__dict__ is not like that. Depending on how you look at it, its either-or: 1. A *metadata* about an object (object's representation as a dict), and then it makes sense to use a dedicated access means for that metadata, exactly what vars() provides. 2. Leak of an implementation detail, because a particular Python implementation uses a dict as internal storage for modules, classes, instances, and then .__dict__ just gives blatant access to this internal storage, bypassing normal object semantics. -- Best regards, Paul mailto:pmiscml@gmail.com

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Summary of Python tracker Issues
by Python tracker 08 Jan '21

08 Jan '21

ACTIVITY SUMMARY (2021-01-01 - 2021-01-08) 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 7549 ( -7) closed 47055 (+71) total 54604 (+64) Open issues with patches: 3026 Issues opened (39) ================== #42807: smtplib send_message should gives more clear exception if the https://bugs.python.org/issue42807 opened by oon #42808: Add PyType_Type.tp_vectorcall for type(obj) performance https://bugs.python.org/issue42808 opened by Dennis Sweeney #42809: Improve pickle tests for recursive data https://bugs.python.org/issue42809 opened by serhiy.storchaka #42812: @overload-ing method of parent class without actual implementa https://bugs.python.org/issue42812 opened by chaim422 #42813: Extra spaces cause unexpected EOF error in "compile" function https://bugs.python.org/issue42813 opened by xxm #42815: new thread doesn't copy context of the parent thread https://bugs.python.org/issue42815 opened by uriyyo #42819: readline 8.1 bracketed paste https://bugs.python.org/issue42819 opened by dtrodrigues #42820: Sphinx conf.py needs_version entry is outdated https://bugs.python.org/issue42820 opened by timhoffm #42823: Incorrect frame.f_lineno when frame.f_trace is set https://bugs.python.org/issue42823 opened by Mark.Shannon #42825: Build libraries with "/OPT:REF" linker optimization on Windows https://bugs.python.org/issue42825 opened by Austin-Lamb #42827: pegen parser: Multiline eval with assignment to function call: https://bugs.python.org/issue42827 opened by mdk #42830: tempfile mkstemp() leaks file descriptors if os.close() is not https://bugs.python.org/issue42830 opened by mieczyslaw.torchala #42831: IDLE fix colours for MacOS dark mode https://bugs.python.org/issue42831 opened by epaine #42832: classmethod change in 3.9 needs better documentation https://bugs.python.org/issue42832 opened by iritkatriel #42833: Lib/urllib/request.py: digest algorithm should be case insensi https://bugs.python.org/issue42833 opened by Pierre.Tardy #42834: [subinterpreters] Convert "global" static variable caches in _ https://bugs.python.org/issue42834 opened by kj #42836: docs: struct: clarify struct caching behaviour https://bugs.python.org/issue42836 opened by uniq10 #42837: Symbol table incorrectly identifies code as a generator, when https://bugs.python.org/issue42837 opened by Mark.Shannon #42838: Wait for cleanup coroutines before event loop is closed. https://bugs.python.org/issue42838 opened by xloem #42839: SourceFileLoader does not (fully) accept path-like objects https://bugs.python.org/issue42839 opened by favonia #42840: `type` takes **kwargs for __init_subclass__ https://bugs.python.org/issue42840 opened by esoma #42843: What min_sphinx for Python 3.10 https://bugs.python.org/issue42843 opened by mdk #42844: Turtle Module -- "onclick" arguments enchancement https://bugs.python.org/issue42844 opened by sc1341 #42848: asyncio produces an unexpected traceback with recursive __geta https://bugs.python.org/issue42848 opened by asleep-cult #42849: pool worker can't be terminated https://bugs.python.org/issue42849 opened by huangzhesi #42850: Process hangs when calling urllib.request in a multiprocessing https://bugs.python.org/issue42850 opened by fakufaku #42851: Subclassing Enum with ipaddress.IPv4Network/IPv6Network raises https://bugs.python.org/issue42851 opened by felixxm #42853: `OverflowError: signed integer is greater than maximum` in ssl https://bugs.python.org/issue42853 opened by amacd31 #42854: OpenSSL 1.1.1: use SSL_write_ex() and SSL_read_ex() https://bugs.python.org/issue42854 opened by christian.heimes #42855: pathlib.exists on Windows raises an exception on URL like/bad https://bugs.python.org/issue42855 opened by gaborjbernat #42856: ensurepip: add configure --with-wheel-pkg-dir=PATH to get whee https://bugs.python.org/issue42856 opened by vstinner #42859: smtplib: recipe for certifying message delivery https://bugs.python.org/issue42859 opened by dgoldenberg123 #42861: ipaddress - add ability to get next closet subnet of any prefi https://bugs.python.org/issue42861 opened by fasial.mahmood94 #42862: Use functools.lru_cache iso. _sqlite.Cache in sqlite3 module https://bugs.python.org/issue42862 opened by erlendaasland #42863: Python venv inconsistent folder structure on windows https://bugs.python.org/issue42863 opened by jmoguill2 #42864: Improve error messages regarding unclosed parentheses https://bugs.python.org/issue42864 opened by pablogsal #42865: sysconfig appends CFLAGS to LD https://bugs.python.org/issue42865 opened by Greentwip #42867: Entry Widget not editable on Windows 10, but is on Linux Ubunt https://bugs.python.org/issue42867 opened by jmccabe #42868: SpooledTemporaryFile.__iter__ is not transparent to rollover https://bugs.python.org/issue42868 opened by jinoh.kang.kr Most recent 15 issues with no replies (15) ========================================== #42868: SpooledTemporaryFile.__iter__ is not transparent to rollover https://bugs.python.org/issue42868 #42864: Improve error messages regarding unclosed parentheses https://bugs.python.org/issue42864 #42849: pool worker can't be terminated https://bugs.python.org/issue42849 #42844: Turtle Module -- "onclick" arguments enchancement https://bugs.python.org/issue42844 #42838: Wait for cleanup coroutines before event loop is closed. https://bugs.python.org/issue42838 #42836: docs: struct: clarify struct caching behaviour https://bugs.python.org/issue42836 #42834: [subinterpreters] Convert "global" static variable caches in _ https://bugs.python.org/issue42834 #42833: Lib/urllib/request.py: digest algorithm should be case insensi https://bugs.python.org/issue42833 #42832: classmethod change in 3.9 needs better documentation https://bugs.python.org/issue42832 #42830: tempfile mkstemp() leaks file descriptors if os.close() is not https://bugs.python.org/issue42830 #42825: Build libraries with "/OPT:REF" linker optimization on Windows https://bugs.python.org/issue42825 #42820: Sphinx conf.py needs_version entry is outdated https://bugs.python.org/issue42820 #42815: new thread doesn't copy context of the parent thread https://bugs.python.org/issue42815 #42813: Extra spaces cause unexpected EOF error in "compile" function https://bugs.python.org/issue42813 #42808: Add PyType_Type.tp_vectorcall for type(obj) performance https://bugs.python.org/issue42808 Most recent 15 issues waiting for review (15) ============================================= #42865: sysconfig appends CFLAGS to LD https://bugs.python.org/issue42865 #42864: Improve error messages regarding unclosed parentheses https://bugs.python.org/issue42864 #42856: ensurepip: add configure --with-wheel-pkg-dir=PATH to get whee https://bugs.python.org/issue42856 #42851: Subclassing Enum with ipaddress.IPv4Network/IPv6Network raises https://bugs.python.org/issue42851 #42848: asyncio produces an unexpected traceback with recursive __geta https://bugs.python.org/issue42848 #42844: Turtle Module -- "onclick" arguments enchancement https://bugs.python.org/issue42844 #42843: What min_sphinx for Python 3.10 https://bugs.python.org/issue42843 #42837: Symbol table incorrectly identifies code as a generator, when https://bugs.python.org/issue42837 #42836: docs: struct: clarify struct caching behaviour https://bugs.python.org/issue42836 #42834: [subinterpreters] Convert "global" static variable caches in _ https://bugs.python.org/issue42834 #42827: pegen parser: Multiline eval with assignment to function call: https://bugs.python.org/issue42827 #42825: Build libraries with "/OPT:REF" linker optimization on Windows https://bugs.python.org/issue42825 #42823: Incorrect frame.f_lineno when frame.f_trace is set https://bugs.python.org/issue42823 #42819: readline 8.1 bracketed paste https://bugs.python.org/issue42819 #42815: new thread doesn't copy context of the parent thread https://bugs.python.org/issue42815 Top 10 most discussed issues (10) ================================= #41798: [C API] Revisit usage of the PyCapsule C API with multi-phase https://bugs.python.org/issue41798 11 msgs #42812: @overload-ing method of parent class without actual implementa https://bugs.python.org/issue42812 10 msgs #39457: Add an autocommit property to sqlite3.Connection with a PEP 24 https://bugs.python.org/issue39457 9 msgs #42848: asyncio produces an unexpected traceback with recursive __geta https://bugs.python.org/issue42848 9 msgs #42867: Entry Widget not editable on Windows 10, but is on Linux Ubunt https://bugs.python.org/issue42867 9 msgs #42804: Unable to compile the cpython code x86 windows https://bugs.python.org/issue42804 8 msgs #42855: pathlib.exists on Windows raises an exception on URL like/bad https://bugs.python.org/issue42855 8 msgs #42115: Caching infrastructure for the evaluation loop: specialised op https://bugs.python.org/issue42115 7 msgs #42725: PEP 563: Should the behavior change for yield/yield from's https://bugs.python.org/issue42725 7 msgs #42837: Symbol table incorrectly identifies code as a generator, when https://bugs.python.org/issue42837 7 msgs Issues closed (68) ================== #4643: cgitb.html fails if getattr call raises exception https://bugs.python.org/issue4643 closed by iritkatriel #7946: Convoy effect with I/O bound threads and New GIL https://bugs.python.org/issue7946 closed by dabeaz #14014: codecs.StreamWriter.reset contract not fulfilled https://bugs.python.org/issue14014 closed by berker.peksag #14655: traceback module docs should show how to print/fomat an except https://bugs.python.org/issue14655 closed by iritkatriel #15106: Potential Bug in errors.c https://bugs.python.org/issue15106 closed by pablogsal #16132: ctypes incorrectly encodes .format attribute of memory views https://bugs.python.org/issue16132 closed by dabeaz #16894: Function attribute access doesn't invoke methods in dict subcl https://bugs.python.org/issue16894 closed by dabeaz #24464: "sqlite3_enable_shared_cache" deprecation warning when compili https://bugs.python.org/issue24464 closed by berker.peksag #24844: Python 3.5rc1 compilation error with Apple clang 4.2 included https://bugs.python.org/issue24844 closed by dabeaz #26407: csv.writer.writerows masks exceptions from __iter__ https://bugs.python.org/issue26407 closed by serhiy.storchaka #27436: Strange code in selectors.KqueueSelector https://bugs.python.org/issue27436 closed by dabeaz #31951: import curses is broken on windows https://bugs.python.org/issue31951 closed by serhiy.storchaka #32631: IDLE: revise zzdummy.py https://bugs.python.org/issue32631 closed by terry.reedy #32810: Expose ags_gen and agt_gen in asynchronous generators https://bugs.python.org/issue32810 closed by dabeaz #38413: Remove or change "Multithreading" section https://bugs.python.org/issue38413 closed by Vladimir Ryabtsev #39068: Base 85 encoding initialization race condition https://bugs.python.org/issue39068 closed by serhiy.storchaka #39508: no module curses error although i downloaded the module - wind https://bugs.python.org/issue39508 closed by serhiy.storchaka #40810: sqlite3 test CheckTraceCallbackContent fails for sqlite v3.7.3 https://bugs.python.org/issue40810 closed by berker.peksag #40822: Drop support for SQLite pre 3.7.15 https://bugs.python.org/issue40822 closed by erlendaasland #40823: Don't use obsolete unittest.makeSuite() in sqlite3 tests https://bugs.python.org/issue40823 closed by berker.peksag #40959: Remove unused and unneeded function declaration from sqlite3 h https://bugs.python.org/issue40959 closed by berker.peksag #41463: Avoid duplicating jump information from opcode.py in compile.c https://bugs.python.org/issue41463 closed by iritkatriel #41837: Upgrade installers to OpenSSL 1.1.1i https://bugs.python.org/issue41837 closed by steve.dower #42164: Python fails to compile in the Fedora Stable LTO buildbots https://bugs.python.org/issue42164 closed by vstinner #42179: Clarify chaining exceptions in tutorial/errors.rst https://bugs.python.org/issue42179 closed by Vladimir Ryabtsev #42257: platform.libc_ver() doesn't consider in case of executable is https://bugs.python.org/issue42257 closed by lemburg #42425: Possible leak in initialization of errmap for OSError https://bugs.python.org/issue42425 closed by serhiy.storchaka #42455: Add decorator_factory function to functools module https://bugs.python.org/issue42455 closed by ncoghlan #42508: macOS IDLE with Tk 8.6.10 in 3.9.1rc1 universal2 installer fai https://bugs.python.org/issue42508 closed by terry.reedy #42513: Socket.recv hangs https://bugs.python.org/issue42513 closed by Barney Stratford #42541: Tkinter colours wrong on MacOS universal2 https://bugs.python.org/issue42541 closed by epaine #42584: Upgrade macOS and Windows installers to use SQLite 3.34.0 https://bugs.python.org/issue42584 closed by erlendaasland #42587: memoryview rely on _Bool undefined behavior (test_buffer fails https://bugs.python.org/issue42587 closed by vstinner #42637: Python macos11.0 release note tkinter problems in news https://bugs.python.org/issue42637 closed by epaine #42681: Incorrect range checks/documentation in curses https://bugs.python.org/issue42681 closed by serhiy.storchaka #42692: Build fails on macOS when compiler doesn't define __has_builti https://bugs.python.org/issue42692 closed by ned.deily #42756: smtplib.LMTP.connect() raises TypeError if `timeout` is not sp https://bugs.python.org/issue42756 closed by corona10 #42759: Take into acount a Tcl interpreter when compare variables and https://bugs.python.org/issue42759 closed by serhiy.storchaka #42772: randrange() mishandles step when stop is None https://bugs.python.org/issue42772 closed by rhettinger #42789: Do not skip test_curses on non-tty https://bugs.python.org/issue42789 closed by serhiy.storchaka #42794: test_nntplib fails on CI https://bugs.python.org/issue42794 closed by vstinner #42798: pip search fails https://bugs.python.org/issue42798 closed by benjamin.peterson #42803: Traced line number is wrong for "if not __debug__" https://bugs.python.org/issue42803 closed by Mark.Shannon #42805: broken pygame integration into wxpython https://bugs.python.org/issue42805 closed by serhiy.storchaka #42806: Incorrect offsets in new parser for f-string substitutions https://bugs.python.org/issue42806 closed by pablogsal #42810: Nested if/else gets phantom else trace (3.10) https://bugs.python.org/issue42810 closed by Mark.Shannon #42811: Update docs for importlib.util.resolve_name() to use __spec__. https://bugs.python.org/issue42811 closed by brett.cannon #42814: Undefined behavior in Objects/genericaliasobject.c https://bugs.python.org/issue42814 closed by vstinner #42816: Add str.split_iter function https://bugs.python.org/issue42816 closed by serhiy.storchaka #42817: timedelta zeropadding hh https://bugs.python.org/issue42817 closed by krasmussen #42818: AttributeError: 'zipimporter' object has no attribute 'find_sp https://bugs.python.org/issue42818 closed by mowgli #42821: HTMLParser: subsequent duplicate attributes should be ignored https://bugs.python.org/issue42821 closed by ezio.melotti #42822: Missing backslashes in documentation for 3.8 and 3.9 https://bugs.python.org/issue42822 closed by mdk #42824: get_type_hints throws for local class reference https://bugs.python.org/issue42824 closed by gvanrossum #42826: typing.Iterable does not need __getitem__() method https://bugs.python.org/issue42826 closed by josh.r #42828: Python readline module https://bugs.python.org/issue42828 closed by gvanrossum #42829: get_type_hints throws for nested class with __future__ annotat https://bugs.python.org/issue42829 closed by gvanrossum #42835: Can't Built libxml2 When Using Python 3.9.x https://bugs.python.org/issue42835 closed by gvanrossum #42841: Add bitwise or operator to collections.abc Mapping and Mutable https://bugs.python.org/issue42841 closed by gvanrossum #42842: module 'logging' has not attribute 'handlers' https://bugs.python.org/issue42842 closed by vinay.sajip #42845: Third Party Module Installation using pip fails in Python 3.10 https://bugs.python.org/issue42845 closed by gvanrossum #42846: Using _multibytecodec module on Windows, test_threading/embed https://bugs.python.org/issue42846 closed by vstinner #42847: Normalise file encodings in Lib/sqlite3/test/ https://bugs.python.org/issue42847 closed by erlendaasland #42852: pprint fails in transformming non-breaking space https://bugs.python.org/issue42852 closed by serhiy.storchaka #42857: Fails to construct paths lead to "python is likely shutting do https://bugs.python.org/issue42857 closed by gvanrossum #42858: Incorrect return value for os.system() in recognizing import e https://bugs.python.org/issue42858 closed by gvanrossum #42860: Incompatible types in Python grammar https://bugs.python.org/issue42860 closed by lys.nikolaou #42866: test test_multibytecodec: Test_IncrementalEncoder.test_subinte https://bugs.python.org/issue42866 closed by vstinner

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Where is the SQLite module maintainer
by Erlend Aasland 07 Jan '21

07 Jan '21

Hi, everyone. I'm trying to find a reviewer for this trivial PR: https://github.com/python/cpython/pull/20530 (The PR fixes CheckTraceCallbackContent (in the sqlite3 test suite) for SQLite pre 3.7.15.) I've given up hunting for alternative reviewers (a process I find very uncomfortable, since I feel I'm just bugging people who have too much to do with things they're not interested in), so as a last resort, I'm trying the mailing list: Who can help me review code that touches the sqlite3 module code base? I've received a lot of constructive reviews from Victor Stinner, Dong-he Na and Pablo Galindo on my past sqlite3 PR's; thank you so much! I still feel uncomfortable requesting their review, as none of them are sqlite3 module maintainers. Erlend

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Descriptors in dataclasses fields
by Josue Balandrano Coronel 04 Jan '21

04 Jan '21

I've been exploring dataclasses for a few months now and they've proven to be very useful. The only downside is that there's not a simple way to use descriptors. Descriptors only work on class attributes (as per the docs: https://docs.python.org/3/howto/descriptor.html#closing-thoughts). This means that to use a descriptor in a data class we have to use typing.ClassVar like this @dataclass class Item: name: str price: typing.ClassVar[Decimal] = PriceValidator() Which is totally fine because of how descriptors work the previous syntax is a feature in dataclasses, IMHO. But, there's not a straight forward way to pass a value to the descriptor on init. Because ClassVars are not used by @dataclass to do its thing (as per the docs: https://docs.python.org/3/library/dataclasses.html#class-variables) This means that in the example above `price` is not going to be a parameter of the class Item's __init__ method. So the only way to do this is to either create an InitVar field or a regular field and then pass the value to the descriptor in __post_init__ @dataclass class Item: name: str price_val: InitVar[Decimal] price: typing.ClassVar[Decimal] = PriceValidator() def __post_init__(self, price_val: Decimal) -> None: self.price = price_val When using a regular field we can double the field's purpose by making it the field the descriptor is going to use: @dataclass class Item: name: str _price: Decimal price: typing.ClassVar[Decimal] = PriceValidator() def __post_init__(self) -> None: self.price = self._price And then in the descriptor implement __set_name__ like so: def __set_name(self, owner, name): self.name = f"_{name}" Personally, I don't like either option because it adds noice to the data class definition. Using an InitVar is the better option because that variable is clearly defined as init only and it's not present in an instance. Using a regular field adds unnecessary noice to the data class. Also, I think it clashes with the intent of descriptors since they're supposed to manage their data in any way they want. My questions are: - Are my assumptions correct? - Is this the intended behavior? Or what's the preferred way of using a descriptor in a dataclass field? - If this is not intended, could it be possible to add a `descriptor` parameter to the `field` method and treat the field accordingly? I couldn't find any information on the docs or the PEP. I could"ve missed something, sorry if this is the case :) Thanks! -- Josue https://www.rmcomplexity.com

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Python-Dev January 2021