Mailman 3 June 2017 - Python-Dev

[RELEASE] Python 3.6.2rc1 is now available for testing
by Ned Deily 18 Jun '17

18 Jun '17

On behalf of the Python development community and the Python 3.6 release team, I would like to announce the availability of Python 3.6.2rc1. 3.6.2rc1 is the first release candidate for Python 3.6.2, the next maintenance release of Python 3.6. While 3.6.2rc1 is a preview release and, thus, not intended for production environments, we encourage you to explore it and provide feedback via the Python bug tracker (https://bugs.python.org). Please see "What’s New In Python 3.6" for more information: https://docs.python.org/3.6/whatsnew/3.6.html You can find Python 3.6.2rc1 here: https://www.python.org/downloads/release/python-362rc1/ and its change log here: https://docs.python.org/3.6/whatsnew/changelog.html#python-3-6-2-release-ca… 3.6.2 is planned for final release on 2017-06-30 with the next maintenance release expected to follow in about 3 months. More information about the 3.6 release schedule can be found here: https://www.python.org/dev/peps/pep-0494/ -- Ned Deily nad(a)python.org -- []

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PEP 538 (review round 2): Coercing the legacy C locale to a UTF-8 based locale
by Nick Coghlan 17 Jun '17

17 Jun '17

Hi folks, Enough changes have accumulated in PEP 538 since the start of the previous thread that it seems sensible to me to start a new thread specifically covering the current design (which aims to address all the concerns raised in the previous thread). I haven't requoted the PEP in full since it's so long, but will instead refer readers to the web version: https://www.python.org/dev/peps/pep-0538/ I also generated a diff covered the full changes to the PEP text: * https://gist.github.com/ncoghlan/1067805fe673b3735ac854e195747493/revisions (this is the diff covering the last few days of changes Summarising the key technical changes: * to make the runtime behaviour independent of whether or not locale coercion took place, stdin and stderr now always have "surrogateescape" as their error handler in the potential coercion target locales. This means Python will behave the same way regardless of whether the locale gets set externally (e.g. by a parent Python process or a container image definition) or implicitly during CLI startup * for the full locales, the interpreter now sets LC_CTYPE and LANG, *not* LC_ALL. This means LC_ALL is once again a full locale override, and also means that CPython won't inadvertently interfere with other locale categories like LC_MONETARY, LC_NUMERIC, etc * the reference implementation has been refactored so the bulk of the new code lives in the shared library and is exposed to the linker via a couple of underscore prefixed API symbols (_Py_LegacyLocaleDetected() and _Py_CoerceLegacyLocale()). While the current PEP still keeps them private, it would be straightforward to make them public for use in embedding applications if we decided we wanted to do so. * locale coercion and warnings are now enabled by default on all platforms that use the autotools-based build chain - the assumption that some platforms didn't need them turned out to be incorrect In addition to being updated to cover the above changes, the Rationale section of the PEP has also been updated to explain why it doesn't propose setting PYTHONIOENCODING, and to walk through some examples of the problems with GNU readlines compatibility when the current locale isn't set correctly. The essential related changes to the reference implementation can be seen here: * Always set "surrogateescape" for coercion target locales, independently of whether or not coercion occurred: https://github.com/ncoghlan/cpython/commit/188e7807b6d9e49377aacbb287c074e5… * Stop setting LC_ALL: https://github.com/python/peps/commit/2f530ce0d1fd24835ac0c6f984f40db70482a… (There are also some smaller cleanup commits that can be seen by browsing that branch on GitHub) Cheers, Nick. -- Nick Coghlan | ncoghlan(a)gmail.com | Brisbane, Australia

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Language proposal: variable assignment in functional context
by Robert Vanden Eynde 17 Jun '17

17 Jun '17

Hello, I would like to propose an idea for the language but I don't know where I can talk about it. In a nutshell, I would like to be able to write: y = (b+2 for b = a + 1) Or in list comprehension: Y = [b+2 for a in L for b = a+1] Which can already be done like this: Y = [b+2 for a in L for b in [a+1]] Which is less obvious, has a small overhead (iterating over a list) and get messy with multiple assignment: Y = [b+c+2 for a in L for b,c in [(a+1,a+2)]] New syntax would allow to write: Y = [b+c+2 for a in L for b,c = (a+1,a+2)] The parenthesis are needed for syntax reason I think. One could have successive assignements My first example (b+2 for b = a+1) can already be done using ugly syntax using lambda y = (lambda b: b+2)(b=a+1) y = (lambda b: b+2)(a+1) y = (lambda b=a+1: b+2)() Choice of syntax: for is good because it uses current keyword, and the analogy for x = 5 vs for x in [5] is natural. But the "for" loses the meaning of iteration. The use of "with" would maybe sound more logical. Python already have the "functional if", lambdas, list comprehension, but not simple assignment functional style.

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Summary of Python tracker Issues
by Python tracker 16 Jun '17

16 Jun '17

ACTIVITY SUMMARY (2017-06-09 - 2017-06-16) Python tracker at http://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 6034 ( -1) closed 36405 (+70) total 42439 (+69) Open issues with patches: 2366 Issues opened (48) ================== #17870: Python does not provide PyLong_FromIntMax_t() or PyLong_FromUi http://bugs.python.org/issue17870 reopened by Devin Jeanpierre #30616: Cannot use functional API to create enum with zero values http://bugs.python.org/issue30616 opened by Gerrit.Holl #30617: IDLE: Add docstrings and unittests to outwin.py http://bugs.python.org/issue30617 opened by csabella #30618: readlink for pathlib paths http://bugs.python.org/issue30618 opened by smheidrich #30619: typing.Union doc incoherence in case a class and its subclass http://bugs.python.org/issue30619 opened by khyox #30622: Fix NPN guard for OpenSSL 1.1 http://bugs.python.org/issue30622 opened by msopacua #30623: python-nightly import numpy fails since recently http://bugs.python.org/issue30623 opened by Arek Bulski #30625: Documentation is unclear how "y*" and "y#" format units vary http://bugs.python.org/issue30625 opened by Gregory.Szorc #30629: lower() is called twice http://bugs.python.org/issue30629 opened by motoki #30630: Missing MSI files http://bugs.python.org/issue30630 opened by Mark Airey #30633: Python 3.6.1 installation issues on OpenSuse 42.1: ModuleNotFo http://bugs.python.org/issue30633 opened by zopyx #30637: Syntax error reported on compile(...), but not on compile(..., http://bugs.python.org/issue30637 opened by hniksic #30638: Additional dependencies and rule for `make regen-all` http://bugs.python.org/issue30638 opened by serhiy.storchaka #30639: inspect.getfile(obj) calls object repr on failure http://bugs.python.org/issue30639 opened by takluyver #30640: NULL + 1 in _PyFunction_FastCallDict() http://bugs.python.org/issue30640 opened by serhiy.storchaka #30645: imp.py: load_package() appends to its own loop variable http://bugs.python.org/issue30645 opened by Alexandru Ardelean #30647: CODESET error on AMD64 FreeBSD 10.x Shared 3.x caused by the P http://bugs.python.org/issue30647 opened by haypo #30648: test_logout() of test_imaplib.RemoteIMAP_STARTTLSTest failed r http://bugs.python.org/issue30648 opened by haypo #30649: test_utime_current_old() of test_os fails randomy on x86 Windo http://bugs.python.org/issue30649 opened by haypo #30651: test_poplib.test_stls_context() access violation on x86 Window http://bugs.python.org/issue30651 opened by haypo #30652: test_threading_not_handled() of test_socketserver hangs random http://bugs.python.org/issue30652 opened by haypo #30653: test_socket hangs in ThreadableTest.tearDown() on AMD64 FreeBS http://bugs.python.org/issue30653 opened by haypo #30654: signal module always overwrites SIGINT on interpreter shutdown http://bugs.python.org/issue30654 opened by pkerling #30657: Unsafe arithmetic in PyString_DecodeEscape http://bugs.python.org/issue30657 opened by jaybosamiya #30658: Buildbot: don't sent email notification for custom builders http://bugs.python.org/issue30658 opened by haypo #30660: Lossless Optimization of PNG files http://bugs.python.org/issue30660 opened by tfs #30661: Support tarfile.PAX_FORMAT in shutil.make_archive http://bugs.python.org/issue30661 opened by ncoghlan #30662: fix OrderedDict.__init__ docstring to reflect PEP 468 http://bugs.python.org/issue30662 opened by jonathaneunice #30663: IDLE: Add lineno sidebar to editor window http://bugs.python.org/issue30663 opened by louielu #30664: Change unittest's _SubTest to not sort its params when printin http://bugs.python.org/issue30664 opened by eric.smith #30665: pass big values for arg to fcntl.ioctl http://bugs.python.org/issue30665 opened by ukl #30666: IDLE: add tests for autocomplete window. http://bugs.python.org/issue30666 opened by terry.reedy #30667: IDLE: revise doc subsections 'Completions' http://bugs.python.org/issue30667 opened by terry.reedy #30668: DOC: missing word in license.rst http://bugs.python.org/issue30668 opened by csabella #30670: pprint for dict in sorted order or insert order? http://bugs.python.org/issue30670 opened by josephsmeng #30671: dict: improve lookup function http://bugs.python.org/issue30671 opened by Dmitry Rubanovich #30672: PEP 538: Unexpected locale behaviour on Mac OS X http://bugs.python.org/issue30672 opened by ncoghlan #30673: Add -t option (timeout) to Tools/buildbot/test.bat for "AMD64 http://bugs.python.org/issue30673 opened by haypo #30674: IDLE: add docstrings to grep.py http://bugs.python.org/issue30674 opened by csabella #30675: test_zipfile leaks references on Python 3.5 on the wo Refleaks http://bugs.python.org/issue30675 opened by haypo #30677: Enhance documentation of os.mkdir() http://bugs.python.org/issue30677 opened by ebianchi #30678: Widget variable binding does not work if mainloop is called fr http://bugs.python.org/issue30678 opened by Javier Dehesa #30679: __aexit__ not called when `run_until_complete` is interrupted http://bugs.python.org/issue30679 opened by rthr #30680: textwrap should treat Unicode em-dash like ASCII em-dash http://bugs.python.org/issue30680 opened by jonathaneunice #30681: email.utils.parsedate_to_datetime() should return None when da http://bugs.python.org/issue30681 opened by timb07 #30682: f-string assert is too restrictive http://bugs.python.org/issue30682 opened by eric.smith #30683: Enhance doctest support in regrtest --list-cases http://bugs.python.org/issue30683 opened by haypo #30684: datetime.fromtimestamp raises OSError on first day after epoch http://bugs.python.org/issue30684 opened by lazka Most recent 15 issues with no replies (15) ========================================== #30672: PEP 538: Unexpected locale behaviour on Mac OS X http://bugs.python.org/issue30672 #30668: DOC: missing word in license.rst http://bugs.python.org/issue30668 #30667: IDLE: revise doc subsections 'Completions' http://bugs.python.org/issue30667 #30665: pass big values for arg to fcntl.ioctl http://bugs.python.org/issue30665 #30663: IDLE: Add lineno sidebar to editor window http://bugs.python.org/issue30663 #30654: signal module always overwrites SIGINT on interpreter shutdown http://bugs.python.org/issue30654 #30653: test_socket hangs in ThreadableTest.tearDown() on AMD64 FreeBS http://bugs.python.org/issue30653 #30629: lower() is called twice http://bugs.python.org/issue30629 #30622: Fix NPN guard for OpenSSL 1.1 http://bugs.python.org/issue30622 #30619: typing.Union doc incoherence in case a class and its subclass http://bugs.python.org/issue30619 #30618: readlink for pathlib paths http://bugs.python.org/issue30618 #30616: Cannot use functional API to create enum with zero values http://bugs.python.org/issue30616 #30613: Distutils register command creates non-standard multipart data http://bugs.python.org/issue30613 #30607: Extract documentation theme into a separate package http://bugs.python.org/issue30607 #30587: Mock with spec object does not ensure method call signatures http://bugs.python.org/issue30587 Most recent 15 issues waiting for review (15) ============================================= #30680: textwrap should treat Unicode em-dash like ASCII em-dash http://bugs.python.org/issue30680 #30665: pass big values for arg to fcntl.ioctl http://bugs.python.org/issue30665 #30657: Unsafe arithmetic in PyString_DecodeEscape http://bugs.python.org/issue30657 #30604: co_extra_freefuncs is stored thread locally and can lead to cr http://bugs.python.org/issue30604 #30593: sqlite3 executescript does not respect isolation_level? http://bugs.python.org/issue30593 #30560: Py_SetFatalErrorAbortFunc: Allow embedding program to handle f http://bugs.python.org/issue30560 #30541: Add restricted mocks to the python unittest mocking framework http://bugs.python.org/issue30541 #30519: Add daemon argument to Timer http://bugs.python.org/issue30519 #30512: CAN Socket support for NetBSD http://bugs.python.org/issue30512 #30509: Optimize calling type slots http://bugs.python.org/issue30509 #30502: Fix buffer handling of OBJ_obj2txt http://bugs.python.org/issue30502 #30495: IDLE: modernize textview module http://bugs.python.org/issue30495 #30487: DOC: automatically create a venv and install Sphinx when runni http://bugs.python.org/issue30487 #30485: Element.findall(path, dict) doesn't insert null namespace http://bugs.python.org/issue30485 #30484: Garbage Collector can cause Segfault whilst iterating dictiona http://bugs.python.org/issue30484 Top 10 most discussed issues (10) ================================= #29406: asyncio SSL contexts leak sockets after calling close with cer http://bugs.python.org/issue29406 18 msgs #28180: Implementation of the PEP 538: coerce C locale to C.utf-8 http://bugs.python.org/issue28180 15 msgs #17870: Python does not provide PyLong_FromIntMax_t() or PyLong_FromUi http://bugs.python.org/issue17870 10 msgs #28994: Misc fixes and cleanups in error handling C code http://bugs.python.org/issue28994 10 msgs #30523: regrtest: add --list-cases option to only display test case id http://bugs.python.org/issue30523 10 msgs #30673: Add -t option (timeout) to Tools/buildbot/test.bat for "AMD64 http://bugs.python.org/issue30673 10 msgs #29591: Various security vulnerabilities in bundled expat (CVE-2016-07 http://bugs.python.org/issue29591 9 msgs #30623: python-nightly import numpy fails since recently http://bugs.python.org/issue30623 9 msgs #30671: dict: improve lookup function http://bugs.python.org/issue30671 8 msgs #30571: Add integer formatting code for fixed-width signed arithmetic http://bugs.python.org/issue30571 7 msgs Issues closed (69) ================== #6519: Reorder 'with' statement for files in Python Tutorial http://bugs.python.org/issue6519 closed by Mariatta #11822: Improve disassembly to show embedded code objects http://bugs.python.org/issue11822 closed by serhiy.storchaka #15786: IDLE code completion window can hang or misbehave with mouse http://bugs.python.org/issue15786 closed by terry.reedy #20485: Enable non-ASCII extension module names http://bugs.python.org/issue20485 closed by ncoghlan #23890: assertRaises increases reference counter http://bugs.python.org/issue23890 closed by haypo #24484: multiprocessing cleanup occasionally throws exception http://bugs.python.org/issue24484 closed by pitrou #24744: Lack of type checks in pkgutil.walk_packages and friends http://bugs.python.org/issue24744 closed by r.david.murray #25409: fnmatch.fnmatch normalizes slashes/backslashes on Windows http://bugs.python.org/issue25409 closed by Mariatta #27425: Tests fail because of git's newline preferences on Windows http://bugs.python.org/issue27425 closed by zach.ware #27585: asyncio.Lock deadlock after cancellation http://bugs.python.org/issue27585 closed by yselivanov #28837: 2to3 does not wrap zip correctly http://bugs.python.org/issue28837 closed by Mariatta #29324: test_aead_aes_gcm fails on Kernel 4.9 http://bugs.python.org/issue29324 closed by nascheme #29478: email.policy.Compat32(max_line_length=None) not as documented http://bugs.python.org/issue29478 closed by Mariatta #29514: Add a test case that prevents magic number changes in minor re http://bugs.python.org/issue29514 closed by ncoghlan #29550: Mac build-installer touch step fails after github conversion http://bugs.python.org/issue29550 closed by ned.deily #29581: __init_subclass__ causes TypeError when used with standard lib http://bugs.python.org/issue29581 closed by serhiy.storchaka #29679: Add @contextlib.asynccontextmanager http://bugs.python.org/issue29679 closed by yselivanov #29721: "abort: repository . not found!" during the build of Python 2. http://bugs.python.org/issue29721 closed by serhiy.storchaka #29743: Closing transport during handshake process leaks open socket http://bugs.python.org/issue29743 closed by yselivanov #29783: Modify codecs.open() to use the io module instead of codecs.St http://bugs.python.org/issue29783 closed by haypo #29905: TypeErrors not formatting values correctly http://bugs.python.org/issue29905 closed by haypo #29931: ipaddress.ip_interface __lt__ check seems to be broken http://bugs.python.org/issue29931 closed by serhiy.storchaka #30039: Resuming a 'yield from' stack is broken if a signal arrives in http://bugs.python.org/issue30039 closed by yselivanov #30149: inspect.signature() doesn't support partialmethod without expl http://bugs.python.org/issue30149 closed by serhiy.storchaka #30192: hashlib module breaks with 64-bit kernel and 32-bit user space http://bugs.python.org/issue30192 closed by Mariatta #30217: Missing entry for the tilde (~) operator in the Index http://bugs.python.org/issue30217 closed by Mariatta #30231: test_imaplib needs a TLS server accepting self-signed certific http://bugs.python.org/issue30231 closed by haypo #30266: AbstractContextManager should support __method__ = None http://bugs.python.org/issue30266 closed by Mariatta #30284: Build CPython out of tree with a read-only source tree http://bugs.python.org/issue30284 closed by haypo #30312: Small correction in set code sample http://bugs.python.org/issue30312 closed by Mariatta #30335: Document deprecated alias of assertNotRegex http://bugs.python.org/issue30335 closed by Mariatta #30395: deadlocked child process after forking on pystate.c's head_mut http://bugs.python.org/issue30395 closed by lukasz.langa #30417: [buildbot] Disable the cpu resources on slow buildbots http://bugs.python.org/issue30417 closed by haypo #30501: Produce optimized code for boolean conditions http://bugs.python.org/issue30501 closed by serhiy.storchaka #30508: "Task exception was never retrieved" reported for a canceled t http://bugs.python.org/issue30508 closed by yselivanov #30524: iter(classmethod, sentinel) broken for Argument Clinic class m http://bugs.python.org/issue30524 closed by haypo #30589: With forkserver, Process.exitcode does not get signal number http://bugs.python.org/issue30589 closed by pitrou #30594: Refcounting mistake in _ssl.c http://bugs.python.org/issue30594 closed by serhiy.storchaka #30600: Error message incorrect when index is called with keyword argu http://bugs.python.org/issue30600 closed by serhiy.storchaka #30603: textwrap: declining indent level has no test case http://bugs.python.org/issue30603 closed by Mariatta #30605: re.compile fails when compiling bytes under `-bb` mode http://bugs.python.org/issue30605 closed by serhiy.storchaka #30608: argparse calculates string widths incorrectly http://bugs.python.org/issue30608 closed by terry.reedy #30609: Python 3.6.1 fails to generate 256 colors on Cygwin based 64-b http://bugs.python.org/issue30609 closed by terry.reedy #30610: Python's libexpat vulnerable to CVE-2016-0718 http://bugs.python.org/issue30610 closed by ned.deily #30611: Windows HTML Help always opens maximized http://bugs.python.org/issue30611 closed by Christian.Ullrich #30614: [EASY][2.7] testInitNonExistentFile() of test_bz2 leaks refere http://bugs.python.org/issue30614 closed by haypo #30615: [EASY][2.7] test_recursive_repr() of test_xml_etree_c leaks re http://bugs.python.org/issue30615 closed by matrixise #30620: textwrap: dedent contains logic that can never execute http://bugs.python.org/issue30620 closed by Mariatta #30621: import json before using json module in tutorial Input and Out http://bugs.python.org/issue30621 closed by Mariatta #30624: selectors should use bare except clauses http://bugs.python.org/issue30624 closed by giampaolo.rodola #30626: "SystemError: <class '_io.TextIOWrapper'> returned NULL withou http://bugs.python.org/issue30626 closed by serhiy.storchaka #30627: Incorrect error message for a few functions called with keywod http://bugs.python.org/issue30627 closed by serhiy.storchaka #30628: why venv install old pip? http://bugs.python.org/issue30628 closed by ncoghlan #30631: Warnings in VS2015 Update 3 32-Bit http://bugs.python.org/issue30631 closed by zach.ware #30632: IDLE: add unittests to test_autocomplete http://bugs.python.org/issue30632 closed by louielu #30634: ctypes.cast(obj,ctypes.c_void_p) invalid return in linux_x64 http://bugs.python.org/issue30634 closed by eryksun #30635: Leak in test_c_locale_coercion http://bugs.python.org/issue30635 closed by ncoghlan #30636: Add PYTHONCOERCECLOCALE to the help of the command line http://bugs.python.org/issue30636 closed by ncoghlan #30641: No way to specify "File name too long" error in except stateme http://bugs.python.org/issue30641 closed by r.david.murray #30642: Fix leaks in idlelib http://bugs.python.org/issue30642 closed by terry.reedy #30643: test_basic_script_no_suffix() of test_multiprocessing_main_han http://bugs.python.org/issue30643 closed by pitrou #30644: [EASY][doc] Document that signal.set_wakeup_fd(-1), unregister http://bugs.python.org/issue30644 closed by pitrou #30646: SQLite: sqlite3_enable_shared_cache() is deprecated http://bugs.python.org/issue30646 closed by ned.deily #30650: lack of right parentheses http://bugs.python.org/issue30650 closed by serhiy.storchaka #30655: speech module http://bugs.python.org/issue30655 closed by serhiy.storchaka #30656: typo in PyModule_New documentation http://bugs.python.org/issue30656 closed by Mariatta #30659: Use ** correctly for "kwargs" in signature of namedtuple._repl http://bugs.python.org/issue30659 closed by Mariatta #30669: json.tool does not accept an --indent flag http://bugs.python.org/issue30669 closed by serhiy.storchaka #30676: [Windows] Potential for GIL deadlock on Windows in threadmodul http://bugs.python.org/issue30676 closed by sdeibel

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Issue #21071: change struct.Struct.format type from bytes to str
by Victor Stinner 16 Jun '17

16 Jun '17

Hi I would like to change struct.Struct.format type from bytes to str. I don't expect that anyone uses this attribute, and struct.Struct() constructor accepts both bytes and str. http://bugs.python.org/issue21071 It's just to be convenient: more functions accept str than bytes in Python 3. Example: print() (python3 -bb raises an exceptions if you pass bytes to print). Is anything opposed to breaking the backward compatibility? Victor

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IMPORTANT: Python 3.6.2 Maintenance Release Release Candidate in 3+ days (Monday 2017-06-12 12:00 UTC)
by Ned Deily 15 Jun '17

15 Jun '17

We are approaching the end of the second calendar quarter of 2017 and, according to PEP 494, it's time to start producing the second maintenance release for the 3.6 series. The schedule calls for the release candidate to be produced on Monday 2017-06-12 UTC. As was the case with previous 3.6.x releases, the plan is for the release candidate to be the same as the final release, that is, no additional changes go in after the release candidate except for any showstopper critical problems that might be discovered with rc1. So please plan to get any security fixes, bug fixes, and documentation changes you think should be in 3.6.2 merged in ASAP. The 3.6.2 final is planned for two weeks following rc1, that is, on 2017-06-26. The next 3.6 maintenance release (3.6.3) is planned to follow about 3 months later, so most likely in 2017-09. A reminder that the 3.6 branch will remain open for checkins throughout the 3.6.2rc and final cycle. Once 3.6.2rc1 is tagged, new commits to the 3.6 branch will release with 3.6.3. As always, if you find any problem in 3.6.2rc1 that you may believe should be corrected in 3.6.2, please ensure the problem is documented in a new or existing open issue on bugs.python.org, ensure that the Priority field of the issue is set to "release blocker", and that "Python 3.6" is included in the selected Versions. Comments or tags on github Pull Requests are NOT sufficient! Thanks again for all of your efforts in bringing 3.6 into the world and for helping now to make it even better! https://www.python.org/dev/peps/pep-0494/ http://cpython-devguide.readthedocs.io -- Ned Deily nad(a)python.org -- []

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IDLE internal layout
by Louie Lu 14 Jun '17

14 Jun '17

(Due to idle-dev mailing list low traffic, this mail was sent to python-dev and idle-dev) Hi all, I'm now trying to figure out IDLE internal relation. I got some module dependency graph and count. The work is at HackMD: https://hackmd.io/IwNg7AphDGBmsFoAsBOCAmZAGMBDBKsArEgruuiEkQCa5YBGsNQA Is there any previous material on this topic? thanks Louie.

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Handle errors in cleanup code
by Serhiy Storchaka 13 Jun '17

13 Jun '17

There is an idiomatic Python code: do_something() try: do_something_other() except: undo_something() raise If an error is raised when execute do_something_other(), then we should first restore the state that was before calling do_something(), and then reraise the exception. It is important that the bare "except" (or "except BaseException") is used, because undo_something() should be executed on any exception. And this is one of few cases where using the bare "except" is correct. But if an error is raised when execute undo_something(), it replaces the original exception which become chaining as the __context__ attribute. The problem is that this can change the type of the exception. If do_something_other() raises SystemExit and undo_something() raises KeyError, the final exception has type KeyError. Yury in the comment for PR 2108 [1] suggested more complicated code: do_something() try: do_something_other() except BaseException as ex: try: undo_something() finally: raise ex Does it mean that we should rewrite every chunk of code similar to the above? And if such cumbersome code is necessary and become common, maybe it needs syntax support in the language? Or changing the semantic of exceptions raised in error handlers and finally blocks? [1] https://github.com/python/cpython/pull/2108

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On "PEP 546 — Backport ssl.MemoryBIO and ssl.SSLObject to Python 2.7"
by Benjamin Peterson 12 Jun '17

12 Jun '17

The reason we're having this conversation at all is probably a matter of timing. If MemoryBIO was in Python 3 when PEP 466 was accepted, it surely would have come along for the ride to 2.7. I believe PEP 466 is generally considered to have produced positive results. PEP 546, carrying no breaking changes, is less risky than PEP 466. The reluctance to bend 2.7 rules is healthy. This PEP is part of the price we pay, though, for making a backwards-incompatible release. The security landscape has and will change over the 10+ python-dev-supported life span of 2.7. During that time, we have an obligation to keep Python 2 secure. Part of that is supporting modern security interfaces, which are features. This change is needed to make another stdlib feature, ensurepip (which is itself yet another 2.7.x backport) work well. Therefore, as 2.7 release manager, I'm accepting the PEP.

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Remove embedded expat library?
by Victor Stinner 11 Jun '17

11 Jun '17

Hi, Python embeds a copy of the expat library which already got two major security vulnerabilities: "CVE-2016-0718: expat bug #537" http://python-security.readthedocs.io/vuln/cve-2016-0718_expat_bug_537.html "Issue #26556: Expat 2.1.1" http://python-security.readthedocs.io/vuln/issue_26556_expat_2.1.1.html Would it be possible to maintain this dependency on an external repository which would be easier to maintain? Like http://svn.python.org/projects/external/ used to build Python on Windows. I expect that all Linux distributions build Python using --with-system-expat. It may become the default? What about macOS and other operating systems? By the way, Zachary Ware is working on converting this repository to Git. I don't know his progress: - https://github.com/python/cpython-bin-deps - https://github.com/python/cpython-source-deps Victor

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