Python-Dev April 2014

python-dev@python.org

120 participants
85 discussions

More compact dictionaries with faster iteration

by Raymond Hettinger

The current memory layout for dictionaries is unnecessarily inefficient. It has a sparse table of 24-byte entries containing the hash value, key pointer, and value pointer. Instead, the 24-byte entries should be stored in a dense table referenced by a sparse table of indices. For example, the dictionary: d = {'timmy': 'red', 'barry': 'green', 'guido': 'blue'} is currently stored as: entries = [['--', '--', '--'], [-8522787127447073495, 'barry', 'green'], ['--', '--', '--'], ['--', '--', '--'], ['--', '--', '--'], [-9092791511155847987, 'timmy', 'red'], ['--', '--', '--'], [-6480567542315338377, 'guido', 'blue']] Instead, the data should be organized as follows: indices = [None, 1, None, None, None, 0, None, 2] entries = [[-9092791511155847987, 'timmy', 'red'], [-8522787127447073495, 'barry', 'green'], [-6480567542315338377, 'guido', 'blue']] Only the data layout needs to change. The hash table algorithms would stay the same. All of the current optimizations would be kept, including key-sharing dicts and custom lookup functions for string-only dicts. There is no change to the hash functions, the table search order, or collision statistics. The memory savings are significant (from 30% to 95% compression depending on the how full the table is). Small dicts (size 0, 1, or 2) get the most benefit. For a sparse table of size t with n entries, the sizes are: curr_size = 24 * t new_size = 24 * n + sizeof(index) * t In the above timmy/barry/guido example, the current size is 192 bytes (eight 24-byte entries) and the new size is 80 bytes (three 24-byte entries plus eight 1-byte indices). That gives 58% compression. Note, the sizeof(index) can be as small as a single byte for small dicts, two bytes for bigger dicts and up to sizeof(Py_ssize_t) for huge dict. In addition to space savings, the new memory layout makes iteration faster. Currently, keys(), values, and items() loop over the sparse table, skipping-over free slots in the hash table. Now, keys/values/items can loop directly over the dense table, using fewer memory accesses. Another benefit is that resizing is faster and touches fewer pieces of memory. Currently, every hash/key/value entry is moved or copied during a resize. In the new layout, only the indices are updated. For the most part, the hash/key/value entries never move (except for an occasional swap to fill a hole left by a deletion). With the reduced memory footprint, we can also expect better cache utilization. For those wanting to experiment with the design, there is a pure Python proof-of-concept here: http://code.activestate.com/recipes/578375 YMMV: Keep in mind that the above size statics assume a build with 64-bit Py_ssize_t and 64-bit pointers. The space savings percentages are a bit different on other builds. Also, note that in many applications, the size of the data dominates the size of the container (i.e. the weight of a bucket of water is mostly the water, not the bucket). Raymond

5 years, 7 months

Semi-official read-only Github mirror of the CPython Mercurial repository

by Eli Bendersky

Hi all, https://github.com/python/cpython is now live as a semi-official, *read only* Github mirror of the CPython Mercurial repository. Let me know if you have any problems/concerns. I still haven't decided how often to update it (considering either just N times a day, or maybe use a Hg hook for batching). Suggestions are welcome. The methodology I used to create it is via hg-fast-export. I also tried to pack and gc the git repo as much as possible before the initial Github push - it went down from almost ~2GB to ~200MB (so this is the size of a fresh clone right now). Eli P.S. thanks Jesse for the keys to https://github.com/python

5 years, 10 months

Reviving restricted mode?

by Guido van Rossum

I've received some enthusiastic emails from someone who wants to revive restricted mode. He started out with a bunch of patches to the CPython runtime using ctypes, which he attached to an App Engine bug: http://code.google.com/p/googleappengine/issues/detail?id=671 Based on his code (the file secure.py is all you need, included in secure.tar.gz) it seems he believes the only security leaks are __subclasses__, gi_frame and gi_code. (I have since convinced him that if we add "restricted" guards to these attributes, he doesn't need the functions added to sys.) I don't recall the exploits that Samuele once posted that caused the death of rexec.py -- does anyone recall, or have a pointer to the threads? -- --Guido van Rossum (home page: http://www.python.org/~guido/)

5 years, 12 months

Status of PEP 3145 - Asynchronous I/O for subprocess.popen

by Antoine Pitrou

Hi, On core-mentorship someone asked about PEP 3145 - Asynchronous I/O for subprocess.popen. I answered that asyncio now has subprocess support (including non-blocking I/O on the three standard stream pipes), so it's not obvious anything else is needed. Should we change the PEP's status to Rejected or Superseded? Regards Antoine.

6 years, 2 months

Summary of Python tracker Issues

by Python tracker

ACTIVITY SUMMARY (2014-01-31 - 2014-02-07) 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 4501 (+17) closed 27813 (+65) total 32314 (+82) Open issues with patches: 2045 Issues opened (65) ================== #12915: Add inspect.locate and inspect.resolve http://bugs.python.org/issue12915 reopened by vinay.sajip #16779: Fix compiler warning when building extension modules on 64-bit http://bugs.python.org/issue16779 reopened by skrah #19363: Python 2.7's future_builtins.map is not compatible with Python http://bugs.python.org/issue19363 reopened by Gareth.Rees #20053: venv and ensurepip are affected by default pip config file http://bugs.python.org/issue20053 reopened by ncoghlan #20461: Argument Clinic included return converters hard code use of `` http://bugs.python.org/issue20461 opened by brett.cannon #20462: Python IDLE auto closed when creating a new file or open exist http://bugs.python.org/issue20462 opened by Bishop #20463: sqlite dumpiter dumps invalid script when virtual tables are u http://bugs.python.org/issue20463 opened by Ronny.Pfannschmidt #20464: Update distutils sample config file in Doc/install/index.rst http://bugs.python.org/issue20464 opened by zach.ware #20465: Upgrade SQLite to 3.8.3 with 3.4.0 Windows and OS X installers http://bugs.python.org/issue20465 opened by ned.deily #20466: Example in Doc/extending/embedding.rst fails to compile cleanl http://bugs.python.org/issue20466 opened by zach.ware #20467: Confusing wording about __init__ http://bugs.python.org/issue20467 opened by BreamoreBoy #20468: resource module documentation is incorrect http://bugs.python.org/issue20468 opened by Kurt.Rose #20469: ssl.getpeercert() should include extensions http://bugs.python.org/issue20469 opened by oninoshiko #20475: pystone.py in 3.4 still uses time.clock(), even though it's ma http://bugs.python.org/issue20475 opened by pfalcon #20476: If new email policies are used, default message factory should http://bugs.python.org/issue20476 opened by r.david.murray #20478: Avoid inadvertently special casing Counter in statistics modul http://bugs.python.org/issue20478 opened by ncoghlan #20479: Efficiently support weight/frequency mappings in the statistic http://bugs.python.org/issue20479 opened by ncoghlan #20480: Add ipaddress property to get name of reverse DNS PTR record http://bugs.python.org/issue20480 opened by leonn #20481: Clarify type coercion rules in statistics module http://bugs.python.org/issue20481 opened by ncoghlan #20482: smtplib.SMTP.sendmail: improve exception message http://bugs.python.org/issue20482 opened by yegle #20483: Missing network resource checks in test_urllib2 & test_smtplib http://bugs.python.org/issue20483 opened by ncoghlan #20484: test_pydoc can alter execution environment causing subsequent http://bugs.python.org/issue20484 opened by ned.deily #20485: Enable non-ASCII extension module names http://bugs.python.org/issue20485 opened by Suzumizaki #20486: msilib: can't close opened database http://bugs.python.org/issue20486 opened by gentoo90 #20487: Odd words in unittest.mock document. http://bugs.python.org/issue20487 opened by naoki #20490: Show clear error message on circular import http://bugs.python.org/issue20490 opened by cool-RR #20491: textwrap: Non-breaking space not honored http://bugs.python.org/issue20491 opened by kunkku #20493: asyncio: OverflowError('timeout is too large') http://bugs.python.org/issue20493 opened by haypo #20495: test_read_pty_output() hangs on FreeBSD 7.2 buildbot http://bugs.python.org/issue20495 opened by haypo #20496: function definition tutorial encourages bad practice http://bugs.python.org/issue20496 opened by aisaac #20497: Unclear word in socket document. http://bugs.python.org/issue20497 opened by naoki #20499: Rounding errors with statistics.variance http://bugs.python.org/issue20499 opened by oscarbenjamin #20500: assertion failed when passing an exception object to sys.exit http://bugs.python.org/issue20500 opened by xdegaye #20501: fileinput module will read whole file into memory when using f http://bugs.python.org/issue20501 opened by gromgull #20503: super behavioru and abstract base classes (either implementati http://bugs.python.org/issue20503 opened by Gerrit.Holl #20504: cgi.FieldStorage, multipart, missing Content-Length http://bugs.python.org/issue20504 opened by srittau #20505: Remove resolution from selectors and granularity from asyncio http://bugs.python.org/issue20505 opened by haypo #20506: Command to display all available Import Library http://bugs.python.org/issue20506 opened by arupchakrav #20507: TypeError from str.join has no message http://bugs.python.org/issue20507 opened by Gareth.Rees #20508: IndexError from ipaddress._BaseNetwork.__getitem__ has no mess http://bugs.python.org/issue20508 opened by Gareth.Rees #20510: Test cases in test_sys don't match the comments http://bugs.python.org/issue20510 opened by Gareth.Rees #20511: asyncio: StreamReader should use bytearray for its internal bu http://bugs.python.org/issue20511 opened by yselivanov #20513: Python 2.7. Script interruption on logoff from 0 session under http://bugs.python.org/issue20513 opened by vScherba #20515: Null pointer dereference in tkinter module http://bugs.python.org/issue20515 opened by christian.heimes #20516: Concurrent.futures base concurrency improvement (with patch) http://bugs.python.org/issue20516 opened by glangford #20517: Support errors with two filenames for errno exceptions http://bugs.python.org/issue20517 opened by larry #20518: multiple inheritance + C extension = possibly unexpected __bas http://bugs.python.org/issue20518 opened by Martin.Teichmann #20519: Replace uuid ctypes usage with an extension module. http://bugs.python.org/issue20519 opened by gustavo #20520: Readline test in test_codecs is broken http://bugs.python.org/issue20520 opened by serhiy.storchaka #20521: [PATCH] Cleanup for "dis" module documentation http://bugs.python.org/issue20521 opened by svenberkvens #20523: global .pdbrc on windows 7 not reachable out of the box http://bugs.python.org/issue20523 opened by mbyt #20524: format error messages should provide context information http://bugs.python.org/issue20524 opened by r.david.murray #20525: Got compiler warning when compiling readline module http://bugs.python.org/issue20525 opened by vajrasky #20526: python: Modules/gcmodule.c:379: visit_decref: Assertion `((gc) http://bugs.python.org/issue20526 opened by haypo #20529: Unittest displays ResourceWarning warnings when running tests, http://bugs.python.org/issue20529 opened by Bernt.Røskar.Brenna #20530: Change the text signature format (again) to be more robust http://bugs.python.org/issue20530 opened by larry #20531: TypeError in e-mail.parser when non-ASCII is present http://bugs.python.org/issue20531 opened by jason.coombs #20532: Mark all tests which use _testcapi as CPython only http://bugs.python.org/issue20532 opened by serhiy.storchaka #20534: Enum tests fail with pickle protocol 4 http://bugs.python.org/issue20534 opened by ethan.furman #20535: run_tests.py: Work around issues 20355 and 20361 http://bugs.python.org/issue20535 opened by Arfrever #20536: statistics._decimal_to_ratio() produces non-integer ratio http://bugs.python.org/issue20536 opened by skrah #20537: logging exc_info parameter should accept exception instances http://bugs.python.org/issue20537 opened by yselivanov #20538: Segfault in UTF-7 incremental decoder http://bugs.python.org/issue20538 opened by serhiy.storchaka #20539: math.factorial may throw OverflowError http://bugs.python.org/issue20539 opened by ncoghlan #20540: Python 3.3/3.4 regression in multiprocessing manager ? http://bugs.python.org/issue20540 opened by Irvin.Probst Most recent 15 issues with no replies (15) ========================================== #20536: statistics._decimal_to_ratio() produces non-integer ratio http://bugs.python.org/issue20536 #20535: run_tests.py: Work around issues 20355 and 20361 http://bugs.python.org/issue20535 #20526: python: Modules/gcmodule.c:379: visit_decref: Assertion `((gc) http://bugs.python.org/issue20526 #20523: global .pdbrc on windows 7 not reachable out of the box http://bugs.python.org/issue20523 #20521: [PATCH] Cleanup for "dis" module documentation http://bugs.python.org/issue20521 #20516: Concurrent.futures base concurrency improvement (with patch) http://bugs.python.org/issue20516 #20513: Python 2.7. Script interruption on logoff from 0 session under http://bugs.python.org/issue20513 #20511: asyncio: StreamReader should use bytearray for its internal bu http://bugs.python.org/issue20511 #20508: IndexError from ipaddress._BaseNetwork.__getitem__ has no mess http://bugs.python.org/issue20508 #20504: cgi.FieldStorage, multipart, missing Content-Length http://bugs.python.org/issue20504 #20503: super behavioru and abstract base classes (either implementati http://bugs.python.org/issue20503 #20500: assertion failed when passing an exception object to sys.exit http://bugs.python.org/issue20500 #20497: Unclear word in socket document. http://bugs.python.org/issue20497 #20496: function definition tutorial encourages bad practice http://bugs.python.org/issue20496 #20486: msilib: can't close opened database http://bugs.python.org/issue20486 Most recent 15 issues waiting for review (15) ============================================= #20540: Python 3.3/3.4 regression in multiprocessing manager ? http://bugs.python.org/issue20540 #20537: logging exc_info parameter should accept exception instances http://bugs.python.org/issue20537 #20535: run_tests.py: Work around issues 20355 and 20361 http://bugs.python.org/issue20535 #20534: Enum tests fail with pickle protocol 4 http://bugs.python.org/issue20534 #20532: Mark all tests which use _testcapi as CPython only http://bugs.python.org/issue20532 #20530: Change the text signature format (again) to be more robust http://bugs.python.org/issue20530 #20525: Got compiler warning when compiling readline module http://bugs.python.org/issue20525 #20523: global .pdbrc on windows 7 not reachable out of the box http://bugs.python.org/issue20523 #20521: [PATCH] Cleanup for "dis" module documentation http://bugs.python.org/issue20521 #20520: Readline test in test_codecs is broken http://bugs.python.org/issue20520 #20519: Replace uuid ctypes usage with an extension module. http://bugs.python.org/issue20519 #20516: Concurrent.futures base concurrency improvement (with patch) http://bugs.python.org/issue20516 #20515: Null pointer dereference in tkinter module http://bugs.python.org/issue20515 #20513: Python 2.7. Script interruption on logoff from 0 session under http://bugs.python.org/issue20513 #20511: asyncio: StreamReader should use bytearray for its internal bu http://bugs.python.org/issue20511 Top 10 most discussed issues (10) ================================= #20480: Add ipaddress property to get name of reverse DNS PTR record http://bugs.python.org/issue20480 21 msgs #20485: Enable non-ASCII extension module names http://bugs.python.org/issue20485 17 msgs #20481: Clarify type coercion rules in statistics module http://bugs.python.org/issue20481 14 msgs #20053: venv and ensurepip are affected by default pip config file http://bugs.python.org/issue20053 13 msgs #20185: Derby #17: Convert 49 sites to Argument Clinic across 13 files http://bugs.python.org/issue20185 12 msgs #20475: pystone.py in 3.4 still uses time.clock(), even though it's ma http://bugs.python.org/issue20475 10 msgs #15216: Support setting the encoding on a text stream after creation http://bugs.python.org/issue15216 9 msgs #20505: Remove resolution from selectors and granularity from asyncio http://bugs.python.org/issue20505 9 msgs #20520: Readline test in test_codecs is broken http://bugs.python.org/issue20520 9 msgs #16296: Patch to fix building on Win32/64 under VS 2010 http://bugs.python.org/issue16296 8 msgs Issues closed (62) ================== #2226: Small _abcoll Bugs / Oddities http://bugs.python.org/issue2226 closed by ncoghlan #7538: HP-UX 11.11 GCC build fails to build modules http://bugs.python.org/issue7538 closed by Arfrever #7717: Compilation fixes for IRIX http://bugs.python.org/issue7717 closed by berker.peksag #11117: Implementing Async IO http://bugs.python.org/issue11117 closed by yselivanov #12187: subprocess.wait() with a timeout uses polling on POSIX http://bugs.python.org/issue12187 closed by haypo #14515: tempfile.TemporaryDirectory documented as returning object but http://bugs.python.org/issue14515 closed by r.david.murray #14665: faulthandler prints tracebacks in reverse order http://bugs.python.org/issue14665 closed by ncoghlan #14854: faulthandler: fatal error with "SystemError: null argument to http://bugs.python.org/issue14854 closed by haypo #17159: Remove explicit type check from inspect.Signature.from_functio http://bugs.python.org/issue17159 closed by yselivanov #17162: Py_LIMITED_API needs a PyType_GenericDealloc http://bugs.python.org/issue17162 closed by loewis #18801: inspect.classify_class_attrs() misclassifies object.__new__() http://bugs.python.org/issue18801 closed by yselivanov #18891: Master patch for content manager addition to email package http://bugs.python.org/issue18891 closed by r.david.murray #19186: expat symbols should be namespaced in pyexpat again http://bugs.python.org/issue19186 closed by python-dev #19320: Tkinter tests ran with wantobjects is false http://bugs.python.org/issue19320 closed by serhiy.storchaka #19334: test_asyncio hanging for 1 hour (non-AIX version) http://bugs.python.org/issue19334 closed by haypo #19652: test_asyncio: test_subprocess_send_signal() hangs on buildbot http://bugs.python.org/issue19652 closed by haypo #19761: test_tk fails on OS X with multiple test case failures with bo http://bugs.python.org/issue19761 closed by serhiy.storchaka #19863: Missing function attributes in 2.7 docs. http://bugs.python.org/issue19863 closed by mark.dickinson #19920: TarFile.list() fails on some files http://bugs.python.org/issue19920 closed by serhiy.storchaka #20029: asyncio.SubprocessProtocol is missing http://bugs.python.org/issue20029 closed by haypo #20102: shutil._make_zipfile possible resource leak http://bugs.python.org/issue20102 closed by python-dev #20136: Logging: StreamHandler does not use OS line separator. http://bugs.python.org/issue20136 closed by vinay.sajip #20137: Logging: RotatingFileHandler computes string length instead of http://bugs.python.org/issue20137 closed by vinay.sajip #20162: Test test_hash_distribution fails on RHEL 6.5 / ppc64 http://bugs.python.org/issue20162 closed by haypo #20311: epoll.poll(timeout) and PollSelector.select(timeout) must roun http://bugs.python.org/issue20311 closed by haypo #20319: concurrent.futures.wait() can block forever even if Futures ha http://bugs.python.org/issue20319 closed by bquinlan #20354: tracemalloc causes segfault in "make profile-opt" http://bugs.python.org/issue20354 closed by haypo #20363: BytesWarnings triggerred by test suite http://bugs.python.org/issue20363 closed by serhiy.storchaka #20368: Tkinter: handle the null character http://bugs.python.org/issue20368 closed by serhiy.storchaka #20400: Add create_read_pipe_protocol/create_write_pipe_protocol to as http://bugs.python.org/issue20400 closed by haypo #20404: Delayed exception using non-text encodings with TextIOWrapper http://bugs.python.org/issue20404 closed by python-dev #20412: Enum and IntEnum classes are not defined in the documentation http://bugs.python.org/issue20412 closed by python-dev #20423: io.StringIO newline param has wrong default http://bugs.python.org/issue20423 closed by pitrou #20426: Compiling a regex with re.DEBUG should force a recompile http://bugs.python.org/issue20426 closed by pitrou #20435: Discrepancy between io.StringIO and _pyio.StringIO with univer http://bugs.python.org/issue20435 closed by pitrou #20445: HAVE_BROKEN_NICE detected incorrectly due to configure.ac typo http://bugs.python.org/issue20445 closed by George.Kouryachy #20452: test_timeout_rounding() of test_asyncio fails on "x86 Ubuntu S http://bugs.python.org/issue20452 closed by haypo #20455: test_asyncio hangs on Windows http://bugs.python.org/issue20455 closed by haypo #20456: Argument Clinic rollup patch, 2014/01/31 http://bugs.python.org/issue20456 closed by larry #20460: Wrong markup in c-api/arg.rst http://bugs.python.org/issue20460 closed by zach.ware #20470: "Fatal Python error: Bus error" on the SPARC Solaris 10 buildb http://bugs.python.org/issue20470 closed by haypo #20471: test_signature_on_class() of test_inspect fails on "AMD64 Free http://bugs.python.org/issue20471 closed by yselivanov #20472: test_write_pty() of test_asyncio fails on "x86 Tiger 3.x" buil http://bugs.python.org/issue20472 closed by haypo #20473: inspect.Signature no longer handles builtin classes correctly http://bugs.python.org/issue20473 closed by yselivanov #20474: test_socket failures on OS X due to fixed "expected failures" http://bugs.python.org/issue20474 closed by ned.deily #20477: Add examples of using the new contentmanager api to the email http://bugs.python.org/issue20477 closed by r.david.murray #20488: importlib title and introduction are out of date http://bugs.python.org/issue20488 closed by brett.cannon #20489: help() fails for zlib Compress and Decompress objects http://bugs.python.org/issue20489 closed by serhiy.storchaka #20492: test_tcl is failing on windows 2.7 http://bugs.python.org/issue20492 closed by serhiy.storchaka #20494: Backport of http://bugs.python.org/issue11849 to Python 2.7 (M http://bugs.python.org/issue20494 closed by python-dev #20498: Update StringIO newline tests http://bugs.python.org/issue20498 closed by serhiy.storchaka #20502: Context.create_decimal_from_float() inconsistent precision for http://bugs.python.org/issue20502 closed by mark.dickinson #20509: logging.config.fileConfig() docs could link to the config file http://bugs.python.org/issue20509 closed by python-dev #20512: Python3.3 segfaults when using big5hkscs encoding http://bugs.python.org/issue20512 closed by ned.deily #20514: Errno 10013 - ipython notebook http://bugs.python.org/issue20514 closed by ned.deily #20522: pandas version 0.13.0 does not give warning when summing float http://bugs.python.org/issue20522 closed by mark.dickinson #20527: multiprocessing.Queue deadlocks after “reader” process dea http://bugs.python.org/issue20527 closed by sbt #20528: fileinput module will read whole file into memory when using f http://bugs.python.org/issue20528 closed by r.david.murray #20533: bug in float arithmetic? http://bugs.python.org/issue20533 closed by zach.ware #20541: os.path.exists() gives wrong answer for Windows special files http://bugs.python.org/issue20541 closed by ncoghlan #20542: Assertion failure in test_readline http://bugs.python.org/issue20542 closed by ncoghlan #1028088: Cookies without values are silently ignored (by design?) http://bugs.python.org/issue1028088 closed by berker.peksag

6 years, 2 months

ConfigParser mangles keys with special chars

by Florian Bruhin

Hi, I noticed configparser does behave in a surprising way when a key has a special meaning in ini-format. Consider this example: >>> cp = configparser.ConfigParser() >>> cp.read_dict({'DEFAULT': {';foo': 'bar'}}) >>> cp.write(sys.stdout) [DEFAULT] ;foo = bar Now when reading this again, ";foo = bar" will be a comment and ignored. There's probably similiar behaviour in other corner cases (like if you'd use "[foo]" as key for example). While it seems ConfigParser doesn't do any escaping as all, I'm thinking it should at least raise some exception when such a value is trying to be set. I'd expect writing something and then reading it back via the same configparser to *always* result in the same data, as long as writing worked without error. Thoughts? Should I submit a bug report? Florian -- () ascii ribbon campaign - stop html mail www.asciiribbon.org /\ www.the-compiler.org | I love long mails http://email.is-not-s.ms/ To give happiness is to deserve happiness.

6 years, 3 months

[issue6839] zipfile can't extract file

by Adam Polkosnik

Gentlemen, I'd like to politely ask for a second pair of eyes on [issue6839]. It's been dragging for a very long time, and the fix is really a change from a raise() to a debugging print. Thanks in advance, Adam Polkosnik

6 years, 3 months

Multiple inheritance from builtin (C) types [still] supported in Python3?

by Paul Sokolovsky

Hello, It's more or less known fact (ref: google) that you can't inherit from multiple generic builtin (as in "coded in C") types: class C(dict, list): pass TypeError: multiple bases have instance lay-out conflict However, more detailed googling led me to this page of a book: http://books.google.com.ua/books?id=JnR9hQA3SncC&pg=PA104&lpg=PA104 , which suggest that there might be adhoc support for some native types to serve as multiple bases together, but it doesn't provide an example. The book is apparently focused on Python2. I tried to look at typeobject.c:best_base(), which throws the quoted error above, and the only special rules I could quickly decipher from it is that it's possible to multi-inherit from a class and its subclass. Intuitively, it can be understood - it makes no sense to do that on the same inheritance level, but can happen with recursive inheritance, and then there's no need for conflict - both classes can be "merged" into subclass. Indeed, following works: import _collections class Foo(_collections.defaultdict, dict): pass (opposite order gives MRO conflict) So, is that it, or disjoint native types are supported as bases somehow? Also, would someone know if a class-subclass case happens for example in stdlib? As the previous question, https://mail.python.org/pipermail/python-dev/2014-April/134342.html this one is to help set adequate requirements for implementing multiple inheritance in MicroPython. Thanks, Paul mailto:pmiscml@gmail.com

6 years, 3 months

API and process questions (sparked by Claudiu Popa on 16104

by Jim J. Jewett

(1) Should fixes to a docstring go in with a patch, even if they aren't related to the changing functionality? Bytestring compilation has several orthogonal parameters. Most -- but not all -- are documented in the docstring. (Specifically, there is no explanation of the rx parameter which acts as a filter, and no mention that symbolic links to directories are ignored.) It is best if a commit changes one small thing at a time. On the other hand, Nick recently posted that the minimal overhead of a patch commit is about half an hour. Is that overhead enough to override the one-issue-per-patch guideline? (2) The patch adds new functionality to use multiple processes in parallel. The normal parameter values are integers indicating how many processes to use. The parameter also needs two special values -- one to indicate "use os.cpu_count", and the other to indicate "don't use multiprocessing at all". (A) Is there a Best Practices for this situation, with two odd cases? (B) Claudiu originally copied the API from a similar APU for regrtest. What is the barrier for "do it sensibly" vs "stick with precedent elsewhere"? (Apparently regrtest treats any negative number as a request for the cpu_count calculation; I suspect that "-5" is more likely to be an escaping error for "5" than it is to be a real request for auto-calculation that just happened to choose -5 instead of -1.) (C) How important is it to keep the API consistent between a top-level CLI command and the internal implementation? At the the moment, the request for cpu_count is handled in the CLI wrapper, and not available to interactive callers. On the other hand, interactive callers could just call cpu_count themselves... (D) How important is it to maintain consistency with other uses of the same tool -- multiprocessing has its own was of requesting auto-calculation. (So someone used to multiprocessing might assume that "None" meant to auto-calculate, as opposed to "don't use multiprocessing at all.") -jJ

6 years, 3 months

Python 2.7.7. on Windows

by Mike Miller

Greetings, I've just woken up and noticed Python 2.7.7 is on track to be released, and in a rather unique event contains a few security enhancements in addition to the usual fixes: http://legacy.python.org/dev/peps/pep-0466/ I thought this might be a good time to make a final plea to fix a long-standing security issue in the installer on Windows. By default it installs Python to the root folder, thereby bypassing filesystem permissions: http://bugs.python.org/issue1284316 The main rationale given (for not using the standard %ProgramFiles%) has been that the full path to python is too long to type, and ease of use is more important than the security benefits given by following Windows conventions. However, adding python to the PATH variable is an alternative solution that would result in even fewer keystrokes needing to be typed at a console, while maintaining system security. As this is an installer setting and not a code change, I gather that the opportunities for code breakage should be fewer. Please consider updating this setting to a more secure and friendly default, for 2.7.7 and 3.5+ as well. -Mike

6 years, 3 months

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Python-Dev April 2014