Mailman 3 January 2001 - Python-Dev

Is X a (sequence|mapping)?
by Ka-Ping Yee Jan. 23, 2001

Jan. 23, 2001

We can implement abstract interfaces (sequence, mapping, number) in Python with the appropriate __special__ methods, but i don't see an easy way to test if something supports one of these abstract interfaces in Python. At the moment, to see if something is a sequence i believe i have to say something like try: x[0] except: # not a sequence else: # okay, it's a sequence or if hasattr(x, '__getitem__') or type(x) in [type(()), type([])]: ... Is there, or should there be, a better way to do this? -- ?!ng

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re: I think my set module is ready for prime time
by Greg Wilson Jan. 23, 2001

Jan. 23, 2001

> > Guido van Rossum: > > There's already a PEP on a set object type, and everybody and their > > aunt has already implemented a set datatype. > Eric Raymond: > Greg's proposal has a couple of problems. > The biggest one is that the interface design isn't very Pythonic -- > ...doesn't exploit the extent to which sets > naturally have common semantics with existing Python sequence types. > This is bad; it means that a lot of code that could otherwise ignore > the difference between lists and sets would have to be specialized > one way or the other for no good reason. I agree with Eric's point; I put the interface design on hold while I went off to try to find an efficient implementation capable of handling mutable values (i.e. one that would allow things like sets of sets). I'm still looking :-(, but would appreciate comments from this list on Eric's interface. Thanks, Greg

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test_grammar failing
by Skip Montanaro Jan. 23, 2001

Jan. 23, 2001

At the end of this: make distclean ; ./configure ; make OPT='-g -pipe' ; make test I get this: rm -f ./Lib/test/*.py[co] PYTHONPATH=./build/lib.`cat platform` ./python -tt ./Lib/test/regrtest.py -l test_grammar name: None, in test_in_func, file './Lib/test/test_grammar.py', line 617 locals: {'x': 2, '[1]': 1, 'l': 0} globals: {} Fatal Python error: compiler did not label name as local or global make: *** [test] Aborted PYTHONPATH=./build/lib.`cat platform` ./python -tt ./Lib/test/regrtest.py -l test_grammar name: None, in test_in_func, file './Lib/test/test_grammar.py', line 617 locals: {'x': 2, '[1]': 1, 'l': 0} globals: {} Fatal Python error: compiler did not label name as local or global make: *** [test] Aborted Any ideas? I notice that Jeremy checked in some changes to test_grammar.py this evening. Skip

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2.1a1 release tonight -- but no nested scopes or weak refs
by Guido van Rossum Jan. 23, 2001

Jan. 23, 2001

We've decided to release 2.1a1 without further ado, but without two big hopeful patches: Jeremy's nested scopes aren't finished and will take considerably more time, and Fred's weak references need more review (I haven't had the time to look at the code). Rather than wait longer, I've decided to try and release 2.1a1 tonight -- there's nothing I'm waiting for now before I can cut a tarball. There will be an alpha2 release around February 1. Please don't make any check-ins until I announce the 2.1a1 release here. (PythonLabs: please mail or phone me if you need to check in a last-minute thing -- I'm tagging the tree now.) More news as it happens, --Guido van Rossum (home page: http://www.python.org/~guido/)

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Re: [Python-Dev] Keyword arg dictionary without keyword arguments
by Jack Jansen Jan. 23, 2001

Jan. 23, 2001

Recently, Guido van Rossum <guido(a)digicool.com> said: > > I get the impression that I'm currently seeing a non-NULL third > > argument in my (C) methods even though the method is called without > > keyword arguments. > > > Is this new semantics that I missed the discussion about, or is this a bug? > > [...] > Do you really need the NULL? The places that I know I was counting on the NULL now have "if ( kw && PyObject_IsTrue(kw))", so I'll just have to hope there aren't any more lingering in there. -- Jack Jansen | ++++ stop the execution of Mumia Abu-Jamal ++++ Jack.Jansen(a)oratrix.com | ++++ if you agree copy these lines to your sig ++++ www.oratrix.nl/~jack | see http://www.xs4all.nl/~tank/spg-l/sigaction.htm

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test___all__ fails if bsddb not available
by Fredrik Lundh Jan. 22, 2001

Jan. 22, 2001

test___all__ test test___all__ failed -- dbhash has no __all__ attribute maybe this test shouldn't depend on optional modules? </F>

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test_sax and site-python
by Jack Jansen Jan. 22, 2001

Jan. 22, 2001

I'm not sure whether this is really a bug, but I had the problem that there was something wrong with the xml package I had installed into my Lib/site-python, and this caused test_sax to complain. If the test stuff is expected to test only the core functionality maybe sys.path should be edited so that it only contains directories that are part of the core distribution? -- Jack Jansen | ++++ stop the execution of Mumia Abu-Jamal ++++ Jack.Jansen(a)oratrix.com | ++++ if you agree copy these lines to your sig ++++ www.oratrix.nl/~jack | ++++ see http://www.xs4all.nl/~tank/ ++++

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Re: [Python-checkins] CVS: python/dist/src/Objects object.c,2.107,2.108
by Jeremy Hylton Jan. 22, 2001

Jan. 22, 2001

>>>>> "GvR" == Guido van Rossum <gvanrossum(a)users.sourceforge.net> writes: GvR> Log Message: Changes to recursive-object comparisons, having to GvR> do with a test case I found where rich comparison of unequal GvR> recursive objects gave unintuituve results. In a discussion GvR> with Tim, where we discovered that our intuition on when a<=b GvR> should be true was failing, we decided to outlaw ordering GvR> comparisons on recursive objects. (Once we have fixed our GvR> intuition and designed a matching algorithm that's practical GvR> and reasonable to implement, we can allow such orderings GvR> again.) Sounds sensible to me! I was quite puzzled about what <= should return for recursive objects. GvR> - Changed the nesting limit to a more reasonable small 20; this GvR> only slows down comparisons of very deeply nested objects GvR> (unlikely to occur in practice), while speeding up GvR> comparisons of recursive objects (previously, this would GvR> first waste time and space on 500 nested comparisons before GvR> it would start detecting recursion). After we talked through this code yesterday, I was also thinking that the limit was too high :-). Jeremy

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I still can't build HTML in a current CVS tree.
by Eric S. Raymond Jan. 22, 2001

Jan. 22, 2001

Fred, I still can't build HTML documentation in a current CVS tree -- same complaint about lib/modindex.html being absent. Can we get this fixed before 2.1 ships? -- <a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a> ...Virtually never are murderers the ordinary, law-abiding people against whom gun bans are aimed. Almost without exception, murderers are extreme aberrants with lifelong histories of crime, substance abuse, psychopathology, mental retardation and/or irrational violence against those around them, as well as other hazardous behavior, e.g., automobile and gun accidents." -- Don B. Kates, writing on statistical patterns in gun crime

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getcode() function in pyexpat.c
by Martin v. Loewis Jan. 22, 2001

Jan. 22, 2001

> A few comments to explain this highly stylized and macro-laden code > would be appreciated. I probably can't do that before 2.1a1, but I promise to suggest something right afterwards. In general, the macro magic is designed to make the many expat callbacks available to Python. RC_HANDLER (for return code) is the most general template; VOID_HANDLER and INT_HANDLER are common specializations. In the core of RC_HANDLER, there a tuple is built and a Python function is called. The code used to do PyEval_CallObject right inside the macro; the call_with_frame feature is new compared to 2.0. It solves the specific problem of incomprehensible tracebacks. In a typical SAX application, the user code calls expatreader.ExpatParser.parse, which in turn calls self._parser.Parse(data, isFinal) Now, in 2.0, a common problem was a traceback self._parser.Parse(data, isFinal) TypeError: not enough arguments; expected 4, got 2 Everybody assumes a problem in the call to Parse; the real problem is in the call to the callback inside RC_HANDLER, which tried to call a user's function with two arguments that expected four. 2.1 would improve this slightly on its own, writing self._parser.Parse(data, isFinal) TypeError: characters() takes exactly 4 arguments (2 given) With that code, you get File "/usr/local/lib/python2.1/xml/sax/expatreader.py", line 81, in feed self._parser.Parse(data, isFinal) File "pyexpat.c", line 379, in CharacterData TypeError: characters() takes exactly 4 arguments (2 given) So that tells you that it is the CharacterData handler that invokes characters(). You are right that the frame object is not used otherwise; it is just there to make a nice traceback. > I simply don't understand what's going on -- and I'm deeply > suspicious that it is the source of whatever problems Tim is seeing > with test_sax. I thought so, too, at first; it turned out that the problem was elsewhere. Regards, Martin

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