Mailman 3 September 2020 - Python-Dev

Ask a Core Dev Anything! (You can even ask Guido!)
by Mariatta 24 Sep '20

24 Sep '20

Made you look! [image: :smile:] Hello Python community! Next month, from October 19-23, Python core developers will be participating in our annual weeklong core dev sprint. As part of the sprint, we will be hosting a Q&A session with participating Python core developers as a way for us to connect and engage with the wider Python community. We would like the wide Python community members (you) to participate and ask a core dev any questions about Python. https://app.sli.do/event/d4ifvw2o Please submit your question before using the link above before September 30. On Tuesday, October 20th, 3 PM US Central time, Python core developers will get together (online) and answer your questions. The session will be recorded and will be posted to The PSF’s YouTube channel. You can see the list of participating core developers here: https://python-core-sprint-2020.readthedocs.io/community_qa.html#core-devs-… If you have general question about the sprint itself, please either open an issue or a discussion item in the core-sprint repository: https://github.com/python/core-sprint Thanks for being part of this community.

1 0

[RELEASE] Python 3.8.6 is now available
by Łukasz Langa 24 Sep '20

24 Sep '20

Python 3.8.6 is the sixth maintenance release of Python 3.8. Go get it here: https://www.python.org/downloads/release/python-386/ <https://www.python.org/downloads/release/python-386/> Maintenance releases for the 3.8 series will continue at regular bi-monthly intervals, with 3.8.7 planned for mid-November 2020. What’s new? The Python 3.8 series is the newest feature release of the Python language, and it contains many new features and optimizations. See the “What’s New in Python 3.8 <https://docs.python.org/3.8/whatsnew/3.8.html>” document for more information about features included in the 3.8 series. Python 3.8 is becoming more stable. Our bugfix releases are becoming smaller as we progress. This one contains 122 changes, less than two thirds of the previous average for a new release. Detailed information about all changes made in version 3.8.6 specifically can be found in its change log <https://docs.python.org/release/3.8.6/whatsnew/changelog.html#python-3-8-6>. Note that compared to 3.8.5 this release also contains all changes present in 3.8.6rc1. We hope you enjoy Python 3.8! Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organization contributions to the Python Software Foundation. Your friendly release team, Ned Deily @nad <https://discuss.python.org/u/nad> Steve Dower @steve.dower <https://discuss.python.org/u/steve.dower> Łukasz Langa @ambv <https://discuss.python.org/u/ambv>

1 0

Understanding why object defines rich comparison methods
by Steven D'Aprano 23 Sep '20

23 Sep '20

Why does `object` define rich comparison dunders `__lt__` etc? As far as I can tell, `object.__lt__` etc always return NotImplemented. Merely inheriting from object isn't enough to have comparisons work. So why do they exist at all? Other "do nothing" dunders such as `__add__` aren't defined. I've tried searching for answers, and looked at the source code for rich comparisons here: https://github.com/python/cpython/blob/3.8/Objects/object.c read the information here and in the PEP: https://docs.python.org/3/c-api/object.html#c.PyObject_RichCompare https://www.python.org/dev/peps/pep-0207/ I'm not sure if I'm looking in the right places, or if I even understand exactly what I'm looking at, but I think the relevent code is in typeobject.c, which defines a type: PyTypeObject PyBaseObject_Type = { PyVarObject_HEAD_INIT(&PyType_Type, 0) "object", /* tp_name */ ... and then sets tp_richcompare to `object_richcompare`. I guess that is enough to define the dunder methods? Since (as far as I can tell) they don't do anything, why do they exist? Thanks in advance. -- Steve

6 7

Tagged pointer experiment: need help to optimize
by Victor Stinner 23 Sep '20

23 Sep '20

Hi, I need to help to attempt to optimize my experimental CPython fork which uses tagged pointers. When I proposed my PEP 620 "Hide implementation details from the C API", I was asked about a proof that the PEP unlocks real optimization possibilities. So I wrote an implementation of tagged pointers: https://github.com/vstinner/cpython/pull/6 The main benefit is the memory usage. For example, list(range(200)) uses 1656 bytes instead of 7262 (4x less memory). Sadly, my current simple implementation is 1.1x slower than the reference. I suspect that adding a condition to Py_INCREF() and Py_DECREF() explains a large part of this overhead. My implementation uses tagged pointers for: * integers in the range: [-5; 256] * None, True and False singletons It would be nice to use tagged pointers for a wide range of integer numbers, but I wrote a simple implementation: _Py_TAGPTR_UNBOX() has to return a borrowed reference. This function should return a strong reference to support a larger range. More information in the document: https://github.com/vstinner/cpython/blob/tagged_ptr/TAGGED_POINTERS.rst Victor -- Night gathers, and now my watch begins. It shall not end until my death.

6 13

unable to create PR on github
by Ethan Furman 23 Sep '20

23 Sep '20

The green "create pull request" button is greyed out. I've tried reselecting the repos and branches, logging out and in, navigating to that screen via my own repository -- nothing is working. Any ideas? Thanks. -- ~Ethan~

5 6

Re: PEP 622 version 2 (Structural Pattern Matching)
by Jens Gåsemyr Magnus 23 Sep '20

23 Sep '20

It would be fantastic if these were expressions rather than statements. Imagine being able to write things like: ```python @memoized def fibonacci(n): match n: case 0: (return/yield?) 0 case 1: 1 case _: fibonacci(n - 2) + fibonacci(n - 1) ``` Obviously this could be written easily with an if statement, and might not be the best example. But I’ve often encountered situations where I wish I had semantics like this. Jens ------------------------------------------------------------------- The information contained in this message may be CONFIDENTIAL and is intended for the addressee only. Any unauthorized use, dissemination of the information or copying of this message is prohibited. If you are not the addressee, please notify the sender immediately by return e-mail and delete this message. Thank you

1 0

Enum and the Standard Library
by Ethan Furman 22 Sep '20

22 Sep '20

As you may have noticed, Enums are starting to pop up all over the stdlib [1]. To facilitate transforming existing module constants to IntEnums there is `IntEnum._convert_`. In Issue36548 [2] Serhiy modified the __repr__ of RegexFlag: >>> import re >>> re.I re.IGNORECASE I think for converted constants that that looks nice. For anyone that wants the actual value, it is of course available as the `.value` attribute: >>> re.I.value 2 I'm looking for arguments relating to: - should _convert_ make the default __repr__ be module_name.member_name? - should _convert_ make the default __str__ be the same, or be the numeric value? Thank you for your time! -- ~Ethan~ [1] I'm working on making their creation faster. If anyone wanted to convert EnumMeta to C I would be grateful. [2] https://bugs.python.org/issue36548

7 15

Hygenic macros PEP.
by Mark Shannon 19 Sep '20

19 Sep '20

Hi all, I'd like to propose a new PEP for hygienic macros. I'm attempting to reduce the controversy and pain of adding new syntax to Python, ... by adding new syntax. That might sound silly, but I hope to persuade that it isn't. Adding a new feature to the language is always controversial. Before a new module or functionality is added to the standard library, it must usually prove itself as a package on PyPI. (Not always the same package, the value of dataclasses was demonstrated by "attrs".) However, this isn't currently possible with new language features. Any new language feature has pros and cons. It adds expressive power for some (usually experienced) users, but potentially confuses and inconveniences other users (especially beginners). However, it is very hard, if not impossible, to determine whether adding new syntax will be be beneficial or harmful before the syntax is added. Is there a way to add new syntax in a way that allows it be battle tested before adding to the released version of the language? Yes there is, Macros. I'm not talking about C-style macros which do textual substitution, but "hygienic" macros that rewrite the AST during compilation. Macros allow domain specific new syntactic features, without bloating the language or confusing newcomers. In general, I would except macros to be used within libraries, so that those libraries gain the power of their custom macros without making Python ever larger and more complex. However, there is no reason why they cannot be made more widely available. Should a macro become widely used and popular, then it can be considered for adoption into the language. The PEP: https://github.com/markshannon/peps/blob/hygenic-macros/pep-0700.rst Cheers, Mark.

15 34

The Python documentation is now compatible with Sphinx 3.2 and newer
by Victor Stinner 19 Sep '20

19 Sep '20

Hi, The Python 3.8, 3.9 and 3.10 documentation can now be built with Sphinx 3.2+, and Sphinx 2 is still supported. Sphinx 3.0 and 3.1 are not supported. On our continuous integration (CI), the Python 3.10 documentation is now built with Sphinx 3 (version 3.2.1), whereas the Python 3.8 and Python 3.9 documentation is still built with Sphinx 2 (just updated to version 2.4.4). Also, the Sphinx version is now only pinned in a single file (Doc/requirements.txt), rather than 3 files (Doc/requirements.txt, .travis.yml and Doc/Makefile). Thanks to everyone who helped to fix all these documentation build issues! -- Sphinx 3.0 released in April 2020 is backward incompatible with Sphinx 2: the C domain is stricter, and it is no longer possible to build the Python documentation with Sphinx 3.0. I discussed with the Sphinx maintainers. They accepted to add two new options to Sphinx 3.2 to add an opt-in Sphinx 2 compatibility mode: # bpo-40204: Allow Sphinx 2 syntax in the C domain c_allow_pre_v3 = True # bpo-40204: Disable warnings on Sphinx 2 syntax of the C domain since the # Python documentation is built with -W (warnings treated as errors). c_warn_on_allowed_pre_v3 = False I modified Doc/conf.py to use these options. I also fixed other real documentation issues, discovered by stricter Sphinx 3: https://bugs.python.org/issue40204 -- By the way, all warnings produced during the documentation build have been fixed as well: https://bugs.python.org/issue35293 It took two years (I created the issue in November 2018) to fix all these warnings! Multiple projects got fixes: * Update our Doc/tools/extensions/pyspecific.py extension to fix Sphinx RemovedInSphinx40Warning, by Dong-hee Na * jinja2: https://github.com/pallets/jinja/commit/31bf9b7e71c3fee3b7866ffdc0f70f4525a… (import collections ABC) * python-babel: https://github.com/python-babel/babel/pull/609 (import collections ABC) * docutils: https://sourceforge.net/p/docutils/bugs/373/ (version 0.16 fixed SyntaxWarning on invalid escape sequence) * etc. -- The last remaining minor issue is my proposition to also update Sphinx in docsbuild-scripts (docs.python.org): https://github.com/python/docsbuild-scripts/issues/95 Victor -- Night gathers, and now my watch begins. It shall not end until my death.

3 2

Summary of Python tracker Issues
by Python tracker 18 Sep '20

18 Sep '20

ACTIVITY SUMMARY (2020-09-11 - 2020-09-18) 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 7675 (-22) closed 45870 (+67) total 53545 (+45) Open issues with patches: 3122 Issues opened (29) ================== #41768: unittest.mock spec calls class properties https://bugs.python.org/issue41768 opened by melwitt #41769: Positional arguments which use store boolean actions do not be https://bugs.python.org/issue41769 opened by rjeffman #41770: Import module doesn't updated https://bugs.python.org/issue41770 opened by prasechen #41771: bdist_wininst doesn't execute postinstall script https://bugs.python.org/issue41771 opened by mhammond #41772: Zipfile.testzip considers wrong password as correct https://bugs.python.org/issue41772 opened by Amir #41774: While removing element from list using for and remove(), which https://bugs.python.org/issue41774 opened by sreedevi.ha #41775: IDLE: change Shell window title https://bugs.python.org/issue41775 opened by terry.reedy #41777: When using `python -bb`, `struct.calcsize` raises a warning wh https://bugs.python.org/issue41777 opened by tadeu #41779: add BLOB photo to sqlite3 python https://bugs.python.org/issue41779 opened by alizaerialora #41781: Typos in typing.py https://bugs.python.org/issue41781 opened by pxeger #41784: Promote PyUnicode_AsUTF8AndSize to be available with the limit https://bugs.python.org/issue41784 opened by alex #41787: adding PEP references to documentation https://bugs.python.org/issue41787 opened by cameron #41790: C-API documentation ignores heap types and says type objects m https://bugs.python.org/issue41790 opened by koubaa #41791: mimetypes module does not recognize jp2 type https://bugs.python.org/issue41791 opened by naro #41793: Inaccuracy about reflected operands in datamodel docs. https://bugs.python.org/issue41793 opened by wim.glenn #41794: Memory leak in asyncio server https://bugs.python.org/issue41794 opened by EmperorBale #41796: _ast module state should be made per interpreter https://bugs.python.org/issue41796 opened by vstinner #41797: PyModule_GetState doesn't work with LazyLoader https://bugs.python.org/issue41797 opened by petr.viktorin #41798: [C API] Revisit usage of the PyCapsule C API with multi-phase https://bugs.python.org/issue41798 opened by vstinner #41799: splunklib.client does not handle Unicode characters https://bugs.python.org/issue41799 opened by jpatel #41800: Python installation fails when run under system account if the https://bugs.python.org/issue41800 opened by Jurko.Gospodnetić #41801: 23 tests failed for 3.9.0b2-64 installed on Windows 10 https://bugs.python.org/issue41801 opened by terry.reedy #41802: Missing documentation for 'PyDict_DelItem' behavior https://bugs.python.org/issue41802 opened by ideasman42 #41803: Robots.txt https://bugs.python.org/issue41803 opened by admin2 #41804: test_epoll fails test_control_and_wait() randomly on aarch64 R https://bugs.python.org/issue41804 opened by vstinner #41805: types.GenericAlias and types.Union have no documentation https://bugs.python.org/issue41805 opened by pxeger #41806: socket methods with timeout take very slow path on Windows https://bugs.python.org/issue41806 opened by steve.dower #41807: Warnings when installing Linter on VS code on Linux and Window https://bugs.python.org/issue41807 opened by zamunda #41809: finding file attributes in Windows seems to fail https://bugs.python.org/issue41809 opened by musiquegraeme Most recent 15 issues with no replies (15) ========================================== #41807: Warnings when installing Linter on VS code on Linux and Window https://bugs.python.org/issue41807 #41806: socket methods with timeout take very slow path on Windows https://bugs.python.org/issue41806 #41801: 23 tests failed for 3.9.0b2-64 installed on Windows 10 https://bugs.python.org/issue41801 #41793: Inaccuracy about reflected operands in datamodel docs. https://bugs.python.org/issue41793 #41790: C-API documentation ignores heap types and says type objects m https://bugs.python.org/issue41790 #41781: Typos in typing.py https://bugs.python.org/issue41781 #41775: IDLE: change Shell window title https://bugs.python.org/issue41775 #41771: bdist_wininst doesn't execute postinstall script https://bugs.python.org/issue41771 #41769: Positional arguments which use store boolean actions do not be https://bugs.python.org/issue41769 #41768: unittest.mock spec calls class properties https://bugs.python.org/issue41768 #41761: multiprocessing.Queue prevents program exit when containing a https://bugs.python.org/issue41761 #41754: Webbrowser Module Cannot Find xdg-settings on OSX https://bugs.python.org/issue41754 #41752: Wave shouldn't try to close an open file at all costs https://bugs.python.org/issue41752 #41747: dataclasses: generated method's using the wrong qualname https://bugs.python.org/issue41747 #41738: MIME type for *.zip becomes application/x-zip-compressed on Wi https://bugs.python.org/issue41738 Most recent 15 issues waiting for review (15) ============================================= #41793: Inaccuracy about reflected operands in datamodel docs. https://bugs.python.org/issue41793 #41787: adding PEP references to documentation https://bugs.python.org/issue41787 #41784: Promote PyUnicode_AsUTF8AndSize to be available with the limit https://bugs.python.org/issue41784 #41771: bdist_wininst doesn't execute postinstall script https://bugs.python.org/issue41771 #41768: unittest.mock spec calls class properties https://bugs.python.org/issue41768 #41756: Do not always use exceptions to return result from coroutine https://bugs.python.org/issue41756 #41747: dataclasses: generated method's using the wrong qualname https://bugs.python.org/issue41747 #41746: Add optional type information to asdl_seq objects https://bugs.python.org/issue41746 #41735: Thread locks in zlib module may go wrong in rare case https://bugs.python.org/issue41735 #41734: Refactor b32{encode,decode} tests https://bugs.python.org/issue41734 #41730: Show deprecation warnings for tkinter.tix https://bugs.python.org/issue41730 #41728: Debug logging when adding a TarFile object https://bugs.python.org/issue41728 #41726: Update refcounts info of PyType_FromModuleAndSpec in refcounts https://bugs.python.org/issue41726 #41718: test.regrtest has way too many imports https://bugs.python.org/issue41718 #41713: _signal module leak: test_interpreters leaked [1424, 1422, 142 https://bugs.python.org/issue41713 Top 10 most discussed issues (10) ================================= #41756: Do not always use exceptions to return result from coroutine https://bugs.python.org/issue41756 20 msgs #41602: Python doesn't exit with proper resultcode on SIGINT in runpy https://bugs.python.org/issue41602 12 msgs #41784: Promote PyUnicode_AsUTF8AndSize to be available with the limit https://bugs.python.org/issue41784 9 msgs #41561: test_ssl fails in Ubuntu 20.04: test_min_max_version_mismatch https://bugs.python.org/issue41561 8 msgs #41758: turtledemo.colormixer crashes with a stack overflow https://bugs.python.org/issue41758 8 msgs #41774: While removing element from list using for and remove(), which https://bugs.python.org/issue41774 7 msgs #41745: BoundArguments.arguments used in the recommended way to call a https://bugs.python.org/issue41745 5 msgs #40066: Enum._convert should change __repr__ and/or __str__ to use mod https://bugs.python.org/issue40066 4 msgs #41800: Python installation fails when run under system account if the https://bugs.python.org/issue41800 4 msgs #39452: Improve the __main__ module documentation https://bugs.python.org/issue39452 3 msgs Issues closed (62) ================== #19968: Python does not play well with 'stow'. https://bugs.python.org/issue19968 closed by vinay.sajip #22256: pyvenv should display a progress indicator while creating an e https://bugs.python.org/issue22256 closed by vstinner #23832: pdb's `longlist` shows only decorator if that one contains a l https://bugs.python.org/issue23832 closed by pablogsal #27032: Remove deprecated html.parser.HTMLParser.unescape() https://bugs.python.org/issue27032 closed by terry.reedy #32218: add __iter__ to enum.Flag members https://bugs.python.org/issue32218 closed by ethan.furman #33239: tempfile module: functions with the 'buffering' option are inc https://bugs.python.org/issue33239 closed by vinay.sajip #33561: Add .tostring() method to xml.etree.ElementTree.Element https://bugs.python.org/issue33561 closed by serhiy.storchaka #33813: Update overdue 'Deprecated ... removed in 3.x' messages https://bugs.python.org/issue33813 closed by terry.reedy #33953: The DEFAULT_ENTROPY variable used to store the current default https://bugs.python.org/issue33953 closed by lig #35293: make doctest (Sphinx) emits a lot of warnings https://bugs.python.org/issue35293 closed by vstinner #36586: multiprocessing.Queue.close doesn't behave as documented https://bugs.python.org/issue36586 closed by gvanrossum #37149: link to John Shipman's Tkinter 8.5 documentation fails: websit https://bugs.python.org/issue37149 closed by ned.deily #37296: pdb next vs __next__ https://bugs.python.org/issue37296 closed by ronaldoussoren #37350: print ResourceWarning object traceback when raised as error wi https://bugs.python.org/issue37350 closed by gvanrossum #37479: IntEnum __format__ behavior can't be overridden through __str_ https://bugs.python.org/issue37479 closed by ethan.furman #37604: warnings should use a ContextVar to manage filters/registry https://bugs.python.org/issue37604 closed by gvanrossum #38701: datetime.timedelta string representation is ambiguous https://bugs.python.org/issue38701 closed by lig #38967: Improve error message in enum for member name surrounded by un https://bugs.python.org/issue38967 closed by ethan.furman #39451: enum.Enum reference count leaks https://bugs.python.org/issue39451 closed by ethan.furman #39587: Mixin repr overrides Enum repr in some cases https://bugs.python.org/issue39587 closed by ethan.furman #39651: Exceptions raised by EventLoop.call_soon_threadsafe https://bugs.python.org/issue39651 closed by vstinner #39728: Instantiating enum with invalid value results in ValueError tw https://bugs.python.org/issue39728 closed by ethan.furman #39883: Use BSD0 license for code in docs https://bugs.python.org/issue39883 closed by gvanrossum #40025: enum: _generate_next_value_ is not called if its definition oc https://bugs.python.org/issue40025 closed by ethan.furman #40536: Addition of a "list of available time zones" function to zonei https://bugs.python.org/issue40536 closed by p-ganssle #40616: Add `asyncio.BufferQueue` https://bugs.python.org/issue40616 closed by lig #40721: PEP0435 (enums) -- there is no standard on enum item letters c https://bugs.python.org/issue40721 closed by ethan.furman #41025: C implementation of ZoneInfo cannot be subclassed https://bugs.python.org/issue41025 closed by lukasz.langa #41412: After installation on Windows7, 64bit Python 3.9.0b5 reports " https://bugs.python.org/issue41412 closed by steve.dower #41517: Able to subclass enum with members by using multiple inheritan https://bugs.python.org/issue41517 closed by ethan.furman #41631: _ast module: get_global_ast_state() doesn't work with Mercuria https://bugs.python.org/issue41631 closed by vstinner #41646: shutil.copy documentation should clarify support for path-like https://bugs.python.org/issue41646 closed by steve.dower #41662: Bugs in binding parameters in sqlite3 https://bugs.python.org/issue41662 closed by serhiy.storchaka #41672: imaplib: wrong return type documented https://bugs.python.org/issue41672 closed by corona10 #41715: REDoS in c_analyzer https://bugs.python.org/issue41715 closed by serhiy.storchaka #41719: Why does not range() support decimals? https://bugs.python.org/issue41719 closed by prasechen #41729: test_winconsoleio fails and hangs on Windows https://bugs.python.org/issue41729 closed by terry.reedy #41731: test_cmd_line_script fails with verbosity level more than 1 https://bugs.python.org/issue41731 closed by terry.reedy #41744: NuGet python.props only works in python nuget, not other varia https://bugs.python.org/issue41744 closed by steve.dower #41749: Allow omission of imghdr.what file arg if bytes are given https://bugs.python.org/issue41749 closed by eamanu #41753: subprocess.run on windows does not convert path to string https://bugs.python.org/issue41753 closed by terry.reedy #41757: weakmethod's ref is deleted before weakref's garbage-collect c https://bugs.python.org/issue41757 closed by kratsg #41760: 3.8.6 rc1 documentation fails to build with sphinx 3.2.1 https://bugs.python.org/issue41760 closed by vstinner #41762: Documentation job fails on CIs: duplicate token description of https://bugs.python.org/issue41762 closed by vstinner #41763: IDLE: scale font to Windows' "zoom" factor https://bugs.python.org/issue41763 closed by epaine #41764: sub function would not work without the flags but the search w https://bugs.python.org/issue41764 closed by mrabarnett #41765: tkinter: XFCE task switcher shows 'Tk' instead of Window title https://bugs.python.org/issue41765 closed by terry.reedy #41766: Python3.10 (x64) crashes after flake8/pyflakes on Windows https://bugs.python.org/issue41766 closed by neonene #41767: KeyError exception is more difficult to read due to quoting https://bugs.python.org/issue41767 closed by Anthony Sottile #41773: Clarify handling of infinity and nan in random.choices https://bugs.python.org/issue41773 closed by rhettinger #41776: Revise example of "continue" in the tutorial documentation https://bugs.python.org/issue41776 closed by eric.smith #41778: Change a punctuation on documentation https://bugs.python.org/issue41778 closed by eric.smith #41780: Generic Alias attributes nor in dir() https://bugs.python.org/issue41780 closed by gvanrossum #41782: No f-string in logging.basicConfig() https://bugs.python.org/issue41782 closed by vinay.sajip #41783: Standard Color class https://bugs.python.org/issue41783 closed by mertcandav #41785: Unittest do not support datatime for AlmostEqual method https://bugs.python.org/issue41785 closed by hildogjr #41786: re.RegexFlag.__str__ is incorrect https://bugs.python.org/issue41786 closed by ethan.furman #41788: enhancement: add assertDuration context manager to unittest mo https://bugs.python.org/issue41788 closed by pablogsal #41789: Enum: __str__ and friends sometimes erroneously replaced https://bugs.python.org/issue41789 closed by ethan.furman #41792: No (public) way to dynamically introspect if an annotation is https://bugs.python.org/issue41792 closed by gvanrossum #41795: Allow assignment in yield statement https://bugs.python.org/issue41795 closed by ronaldoussoren #41808: Synchronize What's New in 3.9 master and 3.9 copies https://bugs.python.org/issue41808 closed by terry.reedy

1 0