Re: [Python-Dev] Python-versus-CPython question for __mul__ dispatch
On 15 May 2015 at 10:45, Nathaniel Smith wrote: > Hi all, > > While attempting to clean up some of the more squamous aspects of > numpy's operator dispatch code [1][2], I've encountered a situation > where the semantics we want and are using are possible according to > CPython-the-interpreter, but AFAICT ought not to be possible according > to Python-the-language, i.e., it's not clear to me whether it's > possible even in principle to implement an object that works the way > numpy.ndarray does in any other interpreter. Which makes me a bit > nervous, so I wanted to check if there was any ruling on this. It's a known CPython operand precedence bug due to the fact several of the builtin types only implement sq_concat & sq_repeat without implementing nb_add & nb_mul: http://bugs.python.org/issue11477 There's then a related problem where we *don't* process "NotImplemented" results from sq_concat and sq_repeat properly, so all the builtin sequence types throw TypeError directly, instead of returning NotImplemented when they don't recognise the other type. I wrote a preliminary patch attempting to fix it a few years back after the issue was discovered by Mike Bayer and Alex Gaynor when porting SQL Alchemy to PyPy, but never committed it because my own verdict on the approach I used was that it rendered the abstract object API implementation for __mul__ and __add__ utterly unmaintainable. The better fix would be to make defining sq_concat and sq_repeat more like defining __add__ and __mul__ at the Python level: PyType_Ready should implicitly fill in nb_add and nb_mul references to standard implementations that delegate to sq_concat and sq_repeat, and we should update the implementations of the latter for the standard library sequence types implemented in C to return NotImplemented rather than throwing TypeError directly. However, my intermittent attempts to get anyone else interested in fixing it haven't borne any fruit, and I've prioritised other projects over coming up with a different patch myself. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python-versus-CPython question for __mul__ dispatch
On 15 May 2015 at 16:53, Nathaniel Smith wrote: > On Thu, May 14, 2015 at 9:29 PM, Guido van Rossum wrote: >> I expect you can make something that behaves like list by defining __mul__ >> and __rmul__ and returning NotImplemented. > > Hmm, it's fairly tricky, and part of the trick is that you can never > return NotImplemented (because you have to pretty much take over and > entirely replace the normal dispatch rules inside __mul__ and > __rmul__), but see attached for something I think should work. > > So I guess this is just how Python's list, tuple, etc. work, and PyPy > and friends need to match... No, CPython is broken. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python-versus-CPython question for __mul__ dispatch
On 16 May 2015 at 07:35, Nathaniel Smith wrote: > On Thu, May 14, 2015 at 11:53 PM, Nathaniel Smith wrote: >> On Thu, May 14, 2015 at 9:29 PM, Guido van Rossum wrote: >>> I expect you can make something that behaves like list by defining __mul__ >>> and __rmul__ and returning NotImplemented. >> >> Hmm, it's fairly tricky, and part of the trick is that you can never >> return NotImplemented (because you have to pretty much take over and >> entirely replace the normal dispatch rules inside __mul__ and >> __rmul__), but see attached for something I think should work. >> >> So I guess this is just how Python's list, tuple, etc. work, and PyPy >> and friends need to match... > > For the record, it looks like PyPy does already have a hack to > implement this -- they do it by having a hidden flag on the built-in > sequence types which the implementations of '*' and '+' check for, and > if it's found it triggers a different rule for dispatching to the > __op__ methods: > > https://bitbucket.org/pypy/pypy/src/a1a494787f4112e42f50c6583e0fea18db3fb4fa/pypy/objspace/descroperation.py?at=default#cl-692 Oh, that's rather annoying that the PyPy team implemented bug-for-bug compatibility there, and didn't follow up on the operand precedence bug report to say that they had done so. We also hadn't previously been made aware that NumPy is relying on this operand precedence bug to implement publicly documented API behaviour, so fixing it *would* break end user code :( I guess that means someone in the numeric community will need to write a PEP to make this "try the other operand first" "feature" part of the language specification, so that other interpreters can implement it up front, rather than all having to come up with their own independent custom hacks just to make NumPy work. Regards, Nick. P.S. It would also be nice if someone could take on the PEP for a Python level buffer API for 3.6: http://bugs.python.org/issue13797 -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] No tags in semi-official github mirror of cpython repository.
Hi! On Sat, May 16, 2015 at 11:45:38AM +0900, INADA Naoki wrote: > I foud "semi official github mirror" of cpython. > https://github.com/python/cpython > > I want to use it as upstream of our project (Translating docs in Japanese). > But it doesn't have tags. > > Is the repository stable enough for forking project like us? Or should we > use mercurial? > Could you mirror tags too? If you prefer to use git for development instead of mercurial, like I do, you can try some hg-to-git gateways. I tried hg-fast-export and git-remote-hg and found the latter to be much better. See https://github.com/felipec/git-remote-hg and https://github.com/felipec/git/wiki/Comparison-of-git-remote-hg-alternatives > Thanks > -- > INADA Naoki Oleg. -- Oleg Broytmanhttp://phdru.name/p...@phdru.name Programmers don't die, they just GOSUB without RETURN. ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] cpython (merge 3.4 -> default): Added tests for more builtin types.
In article <20150516183940.21146.77...@psf.io>, serhiy.storchaka wrote: > https://hg.python.org/cpython/rev/7b350f712c0e > changeset: 96099:7b350f712c0e > parent: 96096:f0c94892ac31 > parent: 96098:955dffec3d94 > user:Serhiy Storchaka > date:Sat May 16 21:35:56 2015 +0300 > summary: > Added tests for more builtin types. > Made test_pprint discoverable. > > files: > Lib/test/test_pprint.py | 17 - > 1 files changed, 8 insertions(+), 9 deletions(-) == ERROR: test_coverage (test.test_trace.TestCoverage) -- Traceback (most recent call last): File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 312, in test_coverage self._coverage(tracer) File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 305, in _coverage tracer.run(cmd) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 500, in run self.runctx(cmd, dict, dict) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 508, in runctx exec(cmd, globals, locals) File "", line 1, in AttributeError: module 'test.test_pprint' has no attribute 'test_main' == ERROR: test_coverage_ignore (test.test_trace.TestCoverage) -- Traceback (most recent call last): File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 327, in test_coverage_ignore self._coverage(tracer) File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 305, in _coverage tracer.run(cmd) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 500, in run self.runctx(cmd, dict, dict) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 508, in runctx exec(cmd, globals, locals) File "", line 1, in AttributeError: module 'test.test_pprint' has no attribute 'test_main' Also breaks 3.4. -- Ned Deily, n...@acm.org ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] cpython (merge 3.4 -> default): Added tests for more builtin types.
On 17.05.15 02:44, Ned Deily wrote: In article <20150516183940.21146.77...@psf.io>, serhiy.storchaka wrote: https://hg.python.org/cpython/rev/7b350f712c0e changeset: 96099:7b350f712c0e parent: 96096:f0c94892ac31 parent: 96098:955dffec3d94 user:Serhiy Storchaka date:Sat May 16 21:35:56 2015 +0300 summary: Added tests for more builtin types. Made test_pprint discoverable. files: Lib/test/test_pprint.py | 17 - 1 files changed, 8 insertions(+), 9 deletions(-) == ERROR: test_coverage (test.test_trace.TestCoverage) -- Traceback (most recent call last): File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 312, in test_coverage self._coverage(tracer) File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 305, in _coverage tracer.run(cmd) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 500, in run self.runctx(cmd, dict, dict) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 508, in runctx exec(cmd, globals, locals) File "", line 1, in AttributeError: module 'test.test_pprint' has no attribute 'test_main' == ERROR: test_coverage_ignore (test.test_trace.TestCoverage) -- Traceback (most recent call last): File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 327, in test_coverage_ignore self._coverage(tracer) File "/py/dev/3x/root/uxd/lib/python3.5/test/test_trace.py", line 305, in _coverage tracer.run(cmd) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 500, in run self.runctx(cmd, dict, dict) File "/py/dev/3x/root/uxd/lib/python3.5/trace.py", line 508, in runctx exec(cmd, globals, locals) File "", line 1, in AttributeError: module 'test.test_pprint' has no attribute 'test_main' Also breaks 3.4. Thank you Ned. Opened issue24215 for this because just restoring test_main perhaps not the best way. ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
