Mailman 3 January 2021 - Python-Dev

PEP 651 -- Robust Overflow Handling
by Mark Shannon Jan. 20, 2021

Jan. 20, 2021

Hi everyone, It's time for yet another PEP :) Fortunately, this one is a small one that doesn't change much. It's aim is to make the VM more robust. Abstract ======== This PEP proposes that machine stack overflow is treated differently from runaway recursion. This would allow programs to set the maximum recursion depth to fit their needs and provide additional safety guarantees. The following program will run safely to completion: sys.setrecursionlimit(1_000_000) def f(n): if n: f(n-1) f(500_000) The following program will raise a StackOverflow, without causing a VM crash: sys.setrecursionlimit(1_000_000) class X: def __add__(self, other): return self + other X() + 1 ----------- The full PEP can be found here: https://www.python.org/dev/peps/pep-0651 As always, comments are welcome. Cheers, Mark.

7 21

Advantages of pattern matching - a simple comparative analysis
by Brian Coleman Jan. 19, 2021

Jan. 19, 2021

Take as an example a function designed to process a tree of nodes similar to that which might be output by a JSON parser. There are 4 types of node: - A node representing JSON strings - A node representing JSON numbers - A node representing JSON arrays - A node representing JSON dictionaries The function transforms a tree of nodes, beginning at the root node, and proceeding recursively through each child node in turn. The result is a Python object, with the following transformation applied to each node type: - A JSON string `->` Python `str` - A JSON number `->` Python `float` - A JSON array `->` Python `list` - A JSON dictionary `->` Python `dict` I have implemented this function using 3 different approaches: - The visitor pattern - `isinstance` checks against the node type - Pattern matching Here is the implementation using the visitor pattern: ``` from typing import List, Tuple class NodeVisitor: def visit_string_node(self, node: StringNode): pass def visit_number_node(self, node: NumberNode): pass def visit_list_node(self, node: ListNode): pass def visit_dict_node(self, node: DictNode): pass class Node: def visit(visitor: NodeVisitor): raise NotImplementedError() class StringNode(Node): value: str def visit(self, visitor: NodeVisitor): visitor.visit_string_node(self) class NumberNode(Node): value: str def visit(self, visitor: NodeVisitor): visitor.visit_number_node(self) class ListNode(Node): children: List[Node] def visit(self, visitor: NodeVisitor): visitor.visit_list_node(self) class DictNode(Node): children: List[Tuple[str, Node]] def visit(self, visitor: NodeVisitor): visitor.visit_dict_node(self) class Processor(NodeVisitor): def process(root_node: Node): return root_node.visit(self) def visit_string_node(self, node: StringNode): return node.value def visit_number_node(self, node: NumberNode): return float(node.value) def visit_list_node(self, node: ListNode): return [child_node.visit(self) for child_node in node.children] def visit_dict_node(self, node: DictNode): return {key: child_node.visit(self) for key, child_node in node.children} def process(root_node: Node): processor = Processor() return processor.process(root_node) ``` Here is the implementation using `isinstance` checks against the node type: ``` from typing import List, Tuple class Node: pass class StringNode(Node): value: str class NumberNode(Node): value: str class ListNode(Node): children: List[Node] class DictNode(Node): children: List[Tuple[str, Node]] def process(root_node: Node): def process_node(node: Node): if isinstance(node, StringNode): return node.value elif isinstance(node, NumberNode): return float(node.value) elif isinstance(node, ListNode): return [process_node(child_node) for child_node in node.children] elif isinstance(node, DictNode): return {key: process_node(child_node) for key, child_node in node.children} else: raise Exception('Unexpected node') return process_node(root_node) ``` Finally here is the implementation using pattern matching: ``` from typing import List, Tuple class Node: pass class StringNode(Node): value: str class NumberNode(Node): value: str class ListNode(Node): children: List[Node] class DictNode(Node): children: List[Tuple[str, Node]] def process(root_node: Node): def process_node(node: Node): match node: case StringNode(value=str_value): return str_value case NumberNode(value=number_value): return float(number_value) case ListNode(children=child_nodes): return [process_node(child_node) for child_node in child_nodes] case DictNode(children=child_nodes): return {key: process_node(child_node) for key, child_node in child_nodes} case _: raise Exception('Unexpected node') return process_node(root_node) ``` Here are the lengths of the different implementations: - Pattern matching `->` 37 lines - `isinstance` checks `->` 36 lines - The visitor pattern `->` 69 lines The visitor pattern implementation is by far the most verbose solution, weighing in at almost twice the length of the alternative implementations due to the large amount of boilerplate that is necessary to achieve double dispatch. The pattern matching and `isinstance` check implementations are very similar in length for this trivial example. In each implementation, there are 2 operations performed on each node. - Determine the type of the node - Destructure the node to extract the desired data The visitor pattern and `isinstance` check implementations separate these 2 operations, whereas the pattern matching approach combines the operations together. I believe that it is the declarative nature of pattern matching, where the operations of determining the type of the node and destructuring the node are combined into a single clause, which allows pattern matching to express a concise solution to the problem. In this trivial example, the advantage of pattern matching over the alternative of using a sequence of `if`-`elif`-`else` statements is not as obvious as it would be when compared to a more complex example, where a sub-tree of nodes might be matched based on their type and be destructured in a single clause. I have seen elsewhere an argument that pattern matching should not be accepted into Python as it introduces a pseudo-DSL that is separate from the rest of the language. I agree that pattern matching might be viewed as a pseudo-DSL, but I believe that it is a good thing, if it allows the solution to certain classes of problems to be expressed in a concise manner. People often raise similar objections to operator overloading in other languages, whereas the presence of operator overloading in Python allows mathematical expressions involving custom numeric types such as vectors to be expressed in a natural way. Furthermore, Python has a regular expression module which implements it's own DSL for the purpose of matching string patterns. Regular expressions, in a similar way to pattern matching, allow string patterns to be expressed in a concise and declarative manner. I really hope that the Steering Council accepts pattern matching into Python. I think that it allows for processing of heterogeneous graphs of objects using recursion in a concise, declarative manner. I would like to thank the authors of the Structural Pattern Matching PEP for their hard work in designing this feature and developing an implementation of it. I believe that it will be a wonderful addition to the language that I am very much looking forward to using.

12 25

Should python installation modify /etc/paths.d on Mac OS X?
by Peng Yu Jan. 19, 2021

Jan. 19, 2021

Hi, The /etc/paths.d directory on Mac OS X contains the following directory. Some packages have their PATH variables set there. For Python, I have to set the PATH manually in my ~/.bashrc. Should the Python developers consider setting PATH in /etc/paths.d as well? ==> /etc/paths.d/100-rvictl <== /Library/Apple/usr/bin ==> /etc/paths.d/40-XQuartz <== /opt/X11/bin ==> /etc/paths.d/com.vmware.fusion.public <== /Applications/VMware Fusion.app/Contents/Public -- Regards, Peng

4 4

Unification of the Mac builds?
by Chris Barker Jan. 18, 2021

Jan. 18, 2021

Sorry if I'm out of the loop here, but with Apple's new chip coming out, we need new a build configuration (which I think has already been started, if not done). Perhaps we could take this opportunity to better modularize / unify the build setup? As it was last I checked, you really had only two options: 1) Ignore anything mac specific, and get a "unix" build. 2) Get a full "Framework" build, optionally with Universal support. It would be nice to keep the Framework structure independent of the Mac-specific features, if possible. In particular, I'd love to get be able to get the "pythonw" executable wrapper in an otherwise standard unix build [*]. It would also be nice if it were possible to get universal binaries in a "unix style" build. (option 3 would be to simply abandon the Framework Build altogether -- it's still not clear to me what this really buys mac users) Any chance of this happening? I'm afraid I know nothing of autoconf, so can't be much help, but I'd be willing to help out with testing, or documenting, or anything else that I have the skills to do. Thanks, -Chris [*] The pythonw issue has been a thorn in the side of conda for years. conda uses a standard unix build on the Mac, for consistency with other unix systems. But there is no configuration set up to build the pythonw wrapper outside of a "Framework" build. So instead, conda has creates its own "pythonw" wrapper -- but that is a bash script that re-directs to a different executable. This works fine on the command line (or #! line), but it does not work with setuptools' entry_points. And the setuptools community hasn't shown any interest in hacking around it. Anyway, few enough people develop Desktop apps (particularly with conda) so this has lingered, but it would be nice to fix. -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker(a)noaa.gov

3 5

seg fault in 3.10a4
by Robin Becker Jan. 17, 2021

Jan. 17, 2021

Not sure if this is where I should report, but I have a segfault in reportlab userguide creation with 3.10a4. I am getting this info from coredumpctl running archlinux with Linux hostname 5.10.6-arch1-1 #1 SMP PREEMPT Sat, 09 Jan 2021 18:22:35 +0000 x86_64 GNU/Linux the error is Message: Process 1530711 (python) of user 1000 dumped core. Stack trace of thread 1530711: #0 0x00007f7c9bf72615 raise (libc.so.6 + 0x3d615) #1 0x00007f7c9bf5b862 abort (libc.so.6 + 0x26862) #2 0x00007f7c9bfb45e8 __libc_message (libc.so.6 + 0x7f5e8) #3 0x00007f7c9bfbc27a malloc_printerr (libc.so.6 + 0x8727a) #4 0x00007f7c9bfbd64c _int_free (libc.so.6 + 0x8864c) #5 0x00005631260a01dd n/a (/home/robin/devel/reportlab/.py310/bin/python310 + 0x1401dd) 1) I compile this from source using the standard LTO method my script looks like ########################################### CFLAGS="-march=x86-64 -mtune=generic -O3 -pipe -fno-plt -fno-semantic-interposition" LDFLAGS="-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -rpath=$HOME/LOCAL/3.10.0a4/lib -fno-semantic-interposition" ./configure \ --prefix=$HOME/LOCAL/3.10.0a4 \ --with-computed-gotos \ --enable-optimizations \ --with-lto \ --enable-ipv6 \ --with-system-expat \ --with-dbmliborder=gdbm:ndbm \ --with-system-ffi \ --with-system-libmpdec \ --enable-loadable-sqlite-extensions && make EXTRA_CFLAGS="$CFLAGS" && make install ########################################### 1) can I get more information using a different compile setup 2) or can I get more information with the python run. I just used > $ python genuserguide.py > Built story contains 1843 flowables... > Saved "/home/robin/devel/reportlab/REPOS/reportlab/docs/reportlab-userguide.pdf" > free(): invalid pointer > Aborted (core dumped) 3) I am running in an old style virtual environment generated using a modified virtualenv 16.2.0 (to fix wrong usage of sys.version[:3] in path names) 4) All other tests seem fine including tests of image generation and the accelerated strinGWidths etc etc so I am a bit mystified. -- Robin Becker

4 5

__init_subclass__ and metaclasses
by Ethan Furman Jan. 16, 2021

Jan. 16, 2021

PEP 487 introduced __init_subclass__ and __set_name__, and both of those were wins for the common cases of metaclass usage. Unfortunately, the implementation of PEP 487 with regards to __init_subclass__ has made the writing of correct metaclasses significantly harder, if not impossible. The cause is that when a metaclass calls type.__new__ to actually create the class, type.__new__ calls the __init_subclass__ methods of the new class' parents, passing it the newly created, but incomplete, class. In code: ``` class Meta(type): # def __new__(mcls, name, bases, namespace, **kwds): # create new class, which will call __init_subclass__ and __set_name__ new_class = type.__new__(mcls, name, bases, namespace, **kwds) # finish setting up class new_class.some_attr = 9 ``` As you can deduce, when the parent __init_subclass__ is called with the new class, `some_attr` has not been added yet -- the new class is incomplete. For Enum, this means that __init_subclass__ doesn't have access to the new Enum's members (they haven't beet added yet). For ABC, this means that __init_subclass__ doesn't have access to __abstract_methods__ (it hasn't been created yet). Because Enum is pure Python code I was able to work around it: - remove new __init_subclass__ (if it exists) - insert dummy class with a no-op __init_subclass__ - call type.__new__ - save any actual __init_subclass__ - add back any new __init_subclass__ - rewrite the new class' __bases__, removing the no-op dummy class - finish creating the class - call the parent __init_subclass__ with the now complete Enum class I have not been able to work around the problem for ABC. Two possible solutions I can think of: - pass a keyword argument to type.__new__ that suppresses the call to __init_subclass__; and - provide a way to invoke new class' parent's __init_subclass__ before returning it or - instead of type.__new__ doing that work, have type.__init__ do it. Thoughts? -- ~Ethan~

6 17

Summary of Python tracker Issues
by Python tracker Jan. 15, 2021

Jan. 15, 2021

ACTIVITY SUMMARY (2021-01-08 - 2021-01-15) 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 7546 ( -3) closed 47126 (+71) total 54672 (+68) Open issues with patches: 3027 Issues opened (41) ================== #41837: Upgrade installers to OpenSSL 1.1.1i https://bugs.python.org/issue41837 reopened by christian.heimes #42869: pydoc does not append .html to documentation https://bugs.python.org/issue42869 opened by mdk #42871: Regex compilation crashed if I change order of alternatives un https://bugs.python.org/issue42871 opened by Renji #42872: Inconsistent exceptions thrown by pathlib.Path.mkdir on differ https://bugs.python.org/issue42872 opened by Hong Xu #42874: running configure on Solaris 10 gives grep "illegal option" er https://bugs.python.org/issue42874 opened by martin.wheatley.home #42875: argparse incorrectly shows help string on a new line in case o https://bugs.python.org/issue42875 opened by DiPaolo #42878: urllib.request.HTTPPasswordMgr.is_suburi does not care about o https://bugs.python.org/issue42878 opened by Fongeme #42880: ctypes: variadic function call still doesn't work on Apple Sil https://bugs.python.org/issue42880 opened by lazymio #42881: Should typing.get_type_hints change None annotations? https://bugs.python.org/issue42881 opened by larry #42884: array.index() missing start and end https://bugs.python.org/issue42884 opened by daniel.nicorici #42885: Regex performance problem with ^ aka AT_BEGINNING https://bugs.python.org/issue42885 opened by 2d4d #42887: Multiple assignments of attribute "__sizeof__" will cause a se https://bugs.python.org/issue42887 opened by xxm #42888: Not installed “libgcc_s.so.1” causes parser crash. https://bugs.python.org/issue42888 opened by xxm #42889: Incorrect behavior of Python parser after ast node of test pro https://bugs.python.org/issue42889 opened by xxm #42892: AttributeError in email.message.get_body() https://bugs.python.org/issue42892 opened by xavier2 #42893: Strange XPath search behavior of xml.etree.ElementTree.Element https://bugs.python.org/issue42893 opened by robpats #42894: Debugging native Python modules on Windows with Visual Studio https://bugs.python.org/issue42894 opened by jmoguill2 #42896: Solaris 11.4 crle output not handled correctly https://bugs.python.org/issue42896 opened by dmurphy18 #42897: Expose a way to determine if a process has been closed or not https://bugs.python.org/issue42897 opened by petervansickel #42899: Is it legal to eliminate tests of a value, when that test has https://bugs.python.org/issue42899 opened by stestagg #42901: [Enum] move member creation to __set_name__ in order to suppor https://bugs.python.org/issue42901 opened by ethan.furman #42902: a python embedded program may load "C:\Lib\os.py" on windows https://bugs.python.org/issue42902 opened by houjingyi233 #42904: get_type_hints does not provide localns for classes https://bugs.python.org/issue42904 opened by pbryan #42909: Email header with ;;;; stuffing takes very long to parse https://bugs.python.org/issue42909 opened by eriker #42911: Addition chains for pow saves 5-20% time for pow(int,int) https://bugs.python.org/issue42911 opened by jneb #42913: asyncio.ProactorEventLoop mishandles signal wakeup file descri https://bugs.python.org/issue42913 opened by hidmic #42914: pprint numbers with underscore https://bugs.python.org/issue42914 opened by fov #42915: enum.Flag ~ bitwise negation is very slow and can't be defined https://bugs.python.org/issue42915 opened by aspin2 #42916: Support for DICOM image file format in imghdr module https://bugs.python.org/issue42916 opened by claw #42917: Block stack size for frame objects should be dynamically sizab https://bugs.python.org/issue42917 opened by tomkpz #42918: Nested multi-line expression will lead to "compile()" fails https://bugs.python.org/issue42918 opened by xxm #42919: Blank in multiline “if expressions” will lead to EOF error https://bugs.python.org/issue42919 opened by xxm #42921: Inferred Optional type of wrapper function arguments https://bugs.python.org/issue42921 opened by joperez #42923: Py_FatalError(): dump the list of extension modules https://bugs.python.org/issue42923 opened by vstinner #42924: bytearray_repeat copies from ob_bytes instead of ob_start https://bugs.python.org/issue42924 opened by tholl #42925: Error trace of else inside class https://bugs.python.org/issue42925 opened by ChenXuan #42926: Split compiler into code-gen, optimizer and assembler. https://bugs.python.org/issue42926 opened by Mark.Shannon #42927: Inline cache for slots https://bugs.python.org/issue42927 opened by gvanrossum #42929: On Windows, shutil.move doesn't raise FileExistsError if dst e https://bugs.python.org/issue42929 opened by fireattack #42931: Include randbytes in random.__all__ https://bugs.python.org/issue42931 opened by sbalian #42935: Pickle can't import builtins at exit https://bugs.python.org/issue42935 opened by Wicken Most recent 15 issues with no replies (15) ========================================== #42935: Pickle can't import builtins at exit https://bugs.python.org/issue42935 #42931: Include randbytes in random.__all__ https://bugs.python.org/issue42931 #42921: Inferred Optional type of wrapper function arguments https://bugs.python.org/issue42921 #42919: Blank in multiline “if expressions” will lead to EOF error https://bugs.python.org/issue42919 #42916: Support for DICOM image file format in imghdr module https://bugs.python.org/issue42916 #42897: Expose a way to determine if a process has been closed or not https://bugs.python.org/issue42897 #42875: argparse incorrectly shows help string on a new line in case o https://bugs.python.org/issue42875 #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 #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 Most recent 15 issues waiting for review (15) ============================================= #42931: Include randbytes in random.__all__ https://bugs.python.org/issue42931 #42927: Inline cache for slots https://bugs.python.org/issue42927 #42925: Error trace of else inside class https://bugs.python.org/issue42925 #42924: bytearray_repeat copies from ob_bytes instead of ob_start https://bugs.python.org/issue42924 #42923: Py_FatalError(): dump the list of extension modules https://bugs.python.org/issue42923 #42917: Block stack size for frame objects should be dynamically sizab https://bugs.python.org/issue42917 #42911: Addition chains for pow saves 5-20% time for pow(int,int) https://bugs.python.org/issue42911 #42904: get_type_hints does not provide localns for classes https://bugs.python.org/issue42904 #42901: [Enum] move member creation to __set_name__ in order to suppor https://bugs.python.org/issue42901 #42896: Solaris 11.4 crle output not handled correctly https://bugs.python.org/issue42896 #42892: AttributeError in email.message.get_body() https://bugs.python.org/issue42892 #42875: argparse incorrectly shows help string on a new line in case o https://bugs.python.org/issue42875 #42874: running configure on Solaris 10 gives grep "illegal option" er https://bugs.python.org/issue42874 #42869: pydoc does not append .html to documentation https://bugs.python.org/issue42869 #42865: sysconfig appends CFLAGS to LD https://bugs.python.org/issue42865 Top 10 most discussed issues (10) ================================= #42899: Is it legal to eliminate tests of a value, when that test has https://bugs.python.org/issue42899 24 msgs #42880: ctypes: variadic function call still doesn't work on Apple Sil https://bugs.python.org/issue42880 12 msgs #42927: Inline cache for slots https://bugs.python.org/issue42927 11 msgs #42800: Traceback objects allow accessing frame objects without trigge https://bugs.python.org/issue42800 9 msgs #42862: Use functools.lru_cache iso. _sqlite.Cache in sqlite3 module https://bugs.python.org/issue42862 9 msgs #33809: Expose `capture_locals` parameter in `traceback` convenience f https://bugs.python.org/issue33809 8 msgs #40956: Use Argument Clinic in sqlite3 https://bugs.python.org/issue40956 6 msgs #42888: Not installed “libgcc_s.so.1” causes parser crash. https://bugs.python.org/issue42888 6 msgs #42902: a python embedded program may load "C:\Lib\os.py" on windows https://bugs.python.org/issue42902 6 msgs #42843: What min_sphinx for Python 3.10 https://bugs.python.org/issue42843 5 msgs Issues closed (67) ================== #4480: bdist_msi and bdist_wininst are missing an uninstaller icon https://bugs.python.org/issue4480 closed by vstinner #4636: bdist_wininst installer with install script raises exception https://bugs.python.org/issue4636 closed by vstinner #4878: post installer script's message is not shown to user with bdis https://bugs.python.org/issue4878 closed by vstinner #7833: bdist_wininst installers fail to load extensions built with Is https://bugs.python.org/issue7833 closed by vstinner #8171: bdist_wininst builds wrongly for --plat-name=win-amd64 https://bugs.python.org/issue8171 closed by vstinner #9456: Apparent memory leak in PC/bdist_wininst/install.c https://bugs.python.org/issue9456 closed by vstinner #10945: bdist_wininst depends on MBCS codec, unavailable on non-Window https://bugs.python.org/issue10945 closed by vstinner #11598: missing afxres.h error when building bdist_wininst in Visual S https://bugs.python.org/issue11598 closed by vstinner #12200: bdist_wininst install_script not run on uninstall https://bugs.python.org/issue12200 closed by vstinner #13038: bdist_wininst installers should warn if target dir is read-onl https://bugs.python.org/issue13038 closed by vstinner #13123: bdist_wininst uninstaller does not remove pycache directories https://bugs.python.org/issue13123 closed by vstinner #13276: bdist_wininst-created installer does not run the postinstallat https://bugs.python.org/issue13276 closed by vstinner #14877: No option to run bdist_wininst against newer msvc versions on https://bugs.python.org/issue14877 closed by vstinner #15321: bdist_wininst installers may terminate with "close failed in f https://bugs.python.org/issue15321 closed by vstinner #16081: Fix compile warnings in thread_pthread.h https://bugs.python.org/issue16081 closed by iritkatriel #16615: gcc 4.7 unused-but-set warnings https://bugs.python.org/issue16615 closed by iritkatriel #17419: bdist_wininst installer should allow install in user directory https://bugs.python.org/issue17419 closed by vstinner #21865: Improve invalid category exception for warnings.filterwarnings https://bugs.python.org/issue21865 closed by iritkatriel #25077: Compiler warnings: initialization from incompatible pointer ty https://bugs.python.org/issue25077 closed by iritkatriel #26554: PC\bdist_wininst\install.c: Missing call to fclose() https://bugs.python.org/issue26554 closed by vstinner #33065: IDLE debugger: failure stepping through module loading https://bugs.python.org/issue33065 closed by terry.reedy #33066: raise an exception from multiple positions break the traceback https://bugs.python.org/issue33066 closed by iritkatriel #34705: Python 3.8 changes how returns through finally clauses are tra https://bugs.python.org/issue34705 closed by Mark.Shannon #39273: ncurses does not include BUTTON5_* constants https://bugs.python.org/issue39273 closed by serhiy.storchaka #39690: Compiler warnings in unicodeobject.c https://bugs.python.org/issue39690 closed by iritkatriel #40052: Incorrect pointer alignment in _PyVectorcall_Function() of cpy https://bugs.python.org/issue40052 closed by petr.viktorin #41433: Logging libraries BufferingHandler flushed twice at shutdown https://bugs.python.org/issue41433 closed by iritkatriel #41771: bdist_wininst doesn't execute postinstall script https://bugs.python.org/issue41771 closed by vstinner #41994: Refcount issues in import https://bugs.python.org/issue41994 closed by serhiy.storchaka #42693: "if 0:" lines are traced; they didn't use to be https://bugs.python.org/issue42693 closed by Mark.Shannon #42775: __init_subclass__ should be called in __init__ https://bugs.python.org/issue42775 closed by ethan.furman #42802: distutils: Remove bdist_wininst command https://bugs.python.org/issue42802 closed by vstinner #42827: pegen parser: Multiline eval with assignment to function call: https://bugs.python.org/issue42827 closed by lys.nikolaou #42848: asyncio produces an unexpected traceback with recursive __geta https://bugs.python.org/issue42848 closed by gvanrossum #42850: Process hangs when calling urllib.request in a multiprocessing https://bugs.python.org/issue42850 closed by gvanrossum #42851: Subclassing Enum with ipaddress.IPv4Network/IPv6Network raises https://bugs.python.org/issue42851 closed by ethan.furman #42867: Entry Widget not editable on Windows 10, but is on Linux Ubunt https://bugs.python.org/issue42867 closed by terry.reedy #42870: Document changed argparse output wrt optional arguments in Wha https://bugs.python.org/issue42870 closed by gvanrossum #42873: Exponential time and space requirements for compilation of nes https://bugs.python.org/issue42873 closed by mark.dickinson #42876: '''"""''' != '""""' https://bugs.python.org/issue42876 closed by eryksun #42877: TracebackException saves more data than it needs for format https://bugs.python.org/issue42877 closed by gvanrossum #42879: SystemError from class 'int' https://bugs.python.org/issue42879 closed by mark.dickinson #42882: Restarting the interpreter causes UB on 3.10.0a4 https://bugs.python.org/issue42882 closed by vstinner #42883: __init__ function may incur an incorrect behavior if passing https://bugs.python.org/issue42883 closed by serhiy.storchaka #42886: math.log and math.log10 domain error on very large Fractions https://bugs.python.org/issue42886 closed by gvanrossum #42890: bug float to int https://bugs.python.org/issue42890 closed by christian.heimes #42891: segfault with gunicorn and a library made with cython bindings https://bugs.python.org/issue42891 closed by vstinner #42895: Return multi-line list concatenation without parentheses retur https://bugs.python.org/issue42895 closed by gvanrossum #42898: pickle.loads() crashes interpreter on invalid input https://bugs.python.org/issue42898 closed by christian.heimes #42900: Ternary operator precedence relative to bitwise or https://bugs.python.org/issue42900 closed by gvanrossum #42903: optimize lru_cache for functions with no arguments https://bugs.python.org/issue42903 closed by rhettinger #42905: Issue while installing numba inside fastparquet https://bugs.python.org/issue42905 closed by serhiy.storchaka #42906: python3 -m doctest test.py tests the stdlib "time" module inst https://bugs.python.org/issue42906 closed by gvanrossum #42907: Division betwen float and 100 not giving corect result https://bugs.python.org/issue42907 closed by christian.heimes #42908: Incorrect line numbers at end of try-except and with statement https://bugs.python.org/issue42908 closed by Mark.Shannon #42910: Wrong code appears in the type alias introduction https://bugs.python.org/issue42910 closed by Smile-zjk #42912: enum.Flag ~ bitwise negation is very slow https://bugs.python.org/issue42912 closed by aspin2 #42920: How to add end_lineno in pyclbr? https://bugs.python.org/issue42920 closed by gvanrossum #42922: Enlace a descripción de función 'dir' faltante https://bugs.python.org/issue42922 closed by Mariatta #42928: adafruit_ads1x15.ads1115 not comaptible with globals()[pkg_tru https://bugs.python.org/issue42928 closed by gvanrossum #42930: xml.parsers.expat results differ buffer_text and / or buffer_s https://bugs.python.org/issue42930 closed by mfxuus #42932: How to handle import tripartite pacakge issue in unittest scr https://bugs.python.org/issue42932 closed by gvanrossum #42933: OUTPUT WRONG https://bugs.python.org/issue42933 closed by christian.heimes #42934: use TracebackException's new compact param in unittest.TestRes https://bugs.python.org/issue42934 closed by gvanrossum #42936: Decimal module performs wrong floor division with negative num https://bugs.python.org/issue42936 closed by mark.dickinson #1109963: bdist_wininst ignores build_lib from build command https://bugs.python.org/issue1109963 closed by vstinner #809846: bdist_wininst doesn't clean up read-only files in build dir https://bugs.python.org/issue809846 closed by vstinner

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Bumping minimum Sphinx version to 3.2 for cpython 3.10?
by Julien Palard Jan. 15, 2021

Jan. 15, 2021

During the development of cpython 3.10, Sphinx was bumped to 3.2.1. Problem is Sphinx 3 have some incompatibilities with Sphinx 2, some that we could work around, some are bit harder, so we may need to bump `needs_sphinx = '3.2'` (currently it is 1.8). I found two incompatibilities: - We're using :no-trim-doctest-flags:, introduced in Sphinx 3.2.0, if we build with Sphinx < 3.2.0 the blocks using it are dropped by Sphinx (we use it in library/doctest). - double backslashes in domain directives are no longer replaced by single backslashes. But a configuration value (strip_signature_backslash) can be used to have the same behavior on Sphinx 2 and 3. So yes, it's still possible to build the docs with Sphinx 1.8 using `make html SPHINXERRORHANDLING=`, it "works" but: - Doctests code blocks using no-trim-doctest-flags dissapear. - Some functions declarations are lacking a backslash, like print(*objects, sep=' ', end='n', ... Which is bad. For the first one we could still workaround with an ugly `sed -i /no-trim-doctest-flags/d`, or simply stop using it (and reopen bpo-36675). For the 2nd one we could use `strip_signature_backslash` in cpython 3.10 to have the same behavior. So the question is: Should we bump minimum version of Sphinx from 1.8 to 3.2.1 along with Python 3.10? For the moment this is where we go, but if you're having to maintain a release of Python along with Sphinx < 3, please make speak. Conversation has already started here [1] and here [2]. [1]: https://bugs.python.org/issue42843 [2]: https://github.com/python/cpython/pull/24142 -- [Julien Palard](https://mdk.fr)

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PyGC and PyObject_Malloc introspection
by Julien Danjou Jan. 15, 2021

Jan. 15, 2021

Hi there, I've spent quite some time on memory profiling for Python now. I'm struggling to get more information from the allocated memory right now for what looks like a sad reason. :( Supposedly PyObject_Malloc() returns some memory space to store a PyObject. If that was true all the time, that would allow anyone to introspect the allocated memory and understand why it's being used. Unfortunately, this is not the case. Objects whose types are tracked by the GC go through _PyObject_GC_Alloc() which changes the underlying memory structure to be (PyGC_HEAD + PyObject). This is a bummer as there then no safe way that I can think of to know if an allocated memory space is gc-tracked or gc-untracked. It makes it therefore impossible to introspect the memory allocated by PyObject_Malloc(). There are multiple ways to solve this, but I don't see any way right now of doing this without slightly changing CPython. Has anyone any idea on how to workaround this or the kind of change that could be acceptable to mitigate the issue? Thanks! Cheers, -- Julien Danjou # Free Software hacker # https://julien.danjou.info

4 10

3.10 change (?) for __bool__
by Mats Wichmann Jan. 15, 2021

Jan. 15, 2021

Someone reported a testsuite break on stuff I work on (scons) with 3.10a4, and it looks similar to this which appears in the changelog at https://docs.python.org/3.10/whatsnew/changelog.html#changelog bpo-23898: Fix inspect.classify_class_attrs() to support attributes with overloaded __eq__ and __bool__. Patch by Mike Bayer. Except when I go look at that BPO issue, it's old - closed 2015. Is this appearing in the 3.10 changelog in error? Sorry - confused !!! The test in question does indeed touch a class which overrides __bool_ in order to raise an exception (to say "don't do that"), and in the test run the (expected) exception is not raised.

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