Mailman 3 November 2003 - Python-Dev

RE: [Python-Dev] Banishing apply(), buffer(), coerce(), and intern()
by Delaney, Timothy C (Timothy) 25 Nov '03

25 Nov '03

> From: python-dev-bounces+tdelaney=avaya.com(a)python.org > > After re-reading previous posts on the subject, I had an idea. Let's > isolate these functions in the documentation into a separate section > following the rest of the builtins. Sounds like a good idea to me. I was the person that had a use case for intern(), but would be quite happy for it to be in a less prominent position in the docs - though more prominent than apply ... Cheers. Tim Delaney

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string-valued fget/fset/fdel for properties
by Edward Loper 25 Nov '03

25 Nov '03

I was wondering if there would be any interest for adding a special case for properties with string-valued fget/fset/fdel: - if fget is a string, then the getter returns the value of the member variable with the given name. - if fset is a string, then the setter sets the value of the member variable with the given name. - if fdel is a string, then the deleter deletes the member variable with the given name. I.e., the following groups would be functionally equivalant: property(fget='_foo') property(fget=lambda self: self._foo) property(fget=lambda self: getattr(self, '_foo')) property(fset='_foo') property(fset=lambda self, value: setattr(self, '_foo', value)) property(fdel='_foo') property(fdel=lambda self: delattr(self, '_foo')) This change has 2 advantages: 1. It's easier to read. (In my opinion, anyway; what do other people think?) 2. It's faster: for properties whose fget/fset/fdel are strings, we can avoid a function call (since the changes are implemented in c). Preliminary tests indicate that this results in approximately a 3x speedup for a tight loop of attribute lookups. (It's unclear how much of a speed increase you'd get in actual code, though.) and one disadvantage (that I can think of): - It's one more special case to document/know. This change shouldn't break any existing code, because there's currently no reason to use string-valued fget/fset/fdel. Does this change seem useful to other people? Do the advantages outweigh the disadvantage? Or are there other disadvantage that I neglected to notice? If this seems like a useful addition, I'd be happy to work on making a patch that includes test cases & doc changes. -Edward

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PEP for removal of string module?
by Brett C. 24 Nov '03

24 Nov '03

As I was writing the Summary, I noticed that the discussion of how to handle the removal of the string module got a little complicated thanks to how to deal with stuff that is different between str and unicode. There was no explicit (i.e., patch) resolution to the whole thing. Does this warrant a PEP to work out the details? Now I am not explicitly volunteering to write one since I am no Unicode or locale expert and that seems to be the sticking point. But if one is needed and no one steps forward I guess I could (will have to wait until after generator expressions get implemented, though, since I am already committed to working on that). -Brett

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RE: [Python-Dev] Tail recursion
by Delaney, Timothy C (Timothy) 24 Nov '03

24 Nov '03

> From: Guido van Rossum > > But I have a problem with tail recursion. It's generally requested by > new converts from the Scheme/Lisp or functional programming world, and > it usually means they haven't figured out yet how to write code > without using recursion for everything yet. IOW I'm doubtful on how > much of a difference it would make for real Python programs (which, > simplifying a bit, tend to use loops instead of recursion). And also > note that even if an exception is not caught, you'd like to see all > stack frames listed when the traceback is printed or when the debugger > is invoked. However, that doesn't preclude it from being a thesis subject - in some ways it's actually a bonus as it encourages exploration as it's a direction that is *not* going to be explored by the language designer. It's possible that we could see some truly unexpected benefits come out of this - or there could be no benefits to Python whatsoever. However, from a purely academic point of view, I think it would be a quite reasonable thesis. It allows applying a well-explorered field of research to a new arena. Besides ... sometimes a recursive solution is truly beautiful. Although I think in many (most?) cases a loop on a generator is probably the most appropriate and elegant approach. Tim Delaney

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Re: [Python-checkins] python/dist/src/Lib/idlelib NEWS.txt, 1.25, 1.26 idlever.py, 1.15, 1.16
by Guido van Rossum 24 Nov '03

24 Nov '03

> On Sun, Nov 23, 2003 at 07:23:18PM -0800, kbk(a)users.sourceforge.net wrote: > > + - IDLE now does not fail to save the file anymore if the Tk buffer is not a > > + Unicode string, yet eol_convention is. Python Bugs 774680, 788378 > > The above sentence is unfinished. Not if you assume that the omitted part is "a Unicode string", which I think was intended. --Guido van Rossum (home page: http://www.python.org/~guido/)

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quick patch for better debugging
by Hunter Peress 24 Nov '03

24 Nov '03

Both IndexError and KeyError dont report which object the retrieval failed on. Having this data would save lots of typing and annoyance. Eg: KeyError: 'jio' could look like KeyError: "Dictionary(some_name) has no key 'jio'" IndexError: list index out of range could look like: IndexError: list(some_name) index(some_value) out of range If this is ok, ill make a patch! ----- PS: And for those of you that think even more debugging info is needed, think no more, because I prodded enough a few months ago such that textmode cgitb is now in 2.3 tree. Try: import cgitb; cgitb.enable(format='text') make error here. -- Hunter Peress hunterp(a)fastmail.fm

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by Darrell Hurst 24 Nov '03

24 Nov '03

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Time for 2.3.3?
by Tim Peters 24 Nov '03

24 Nov '03

Over the last week, I checked in fixes for two distinct broad causes of segfaults in code using weakrefs with callbacks. The bugs have been there since weakrefs were introduced, but for whatever reason nobody bumped into them (knowingly) until Jim Fulton and Thomas Heller happened to provoke both, independently, within a day of each other. It was especially easy under Thomas's scenario *not* to get a segfault in a release build, but to suffer random memory corruption instead (if the double-deallocation provoked pymalloc into handing out the same chunk of memory to two distinct objects alive at the same time -- and that is, alas, a likely outcome). I suspect these bugs hid for so long because it's taken Pythoneers a long time to discover why weakrefs can be so cool, and start to build serious apps on top of them. Casual programmers aren't likely to use weakrefs at all, but once you've built a cache based on weakrefs in a large app, weakrefs become critical to your code and your design. So I think either of these fixes is enough to justify a bugfix release, and having two of them makes a compelling case. What say we get 2.3.3 in motion? I did the weakref checkins already on the trunk and on release23-maint; Thomas Heller confirmed that his problems went away on release23-maint, and Jim Fulton confirmed that his Zope3 segfaults went away on the released 2.3.2 + a patch identical in all functional respects to what got checked in (the new test_weakref test cases, and some code comments, were different). If we get 2.3.3c1 out in early December, we could release 2.3.3 final before the end of the year, and start 2004 with a 100% bug-free codebase <wink>.

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Extending struct.unpack to produce nested tuples
by Matthew F. Barnes 23 Nov '03

23 Nov '03

I posted this to c.l.py the other day but didn't get any replies, so I thought I might see how it fares on python-dev. It's just an idea I had earlier this week. I'll attempt a patch if the response is positive. --- I was wondering if there would be any interest in extending the struct.unpack format notation to be able to express groups of data with parenthesis. For example: >>> data = struct.pack('iiii', 1, 2, 3, 4) >>> struct.unpack('i(ii)i', data) # Note the parentheses (1, (2, 3), 4) Use Case: I have a program written in C that contains a bunch of aggregate data structures (arrays of structs, structs containing arrays, etc.) and I'm transmitting these structures over a socket connection to a Python program that then unpacks the data using the struct module. Problem is that I have to unpack the incoming data as a flat sequence of data elements, and then repartition the sequence into nested sequences to better reflect how the data is structured in the C program. It would be more convenient to express these groupings as I'm unpacking the raw data. I'm sure there are plenty of other use cases for such a feature. Matthew Barnes

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Weekly Python Bug/Patch Summary
by Skip Montanaro 23 Nov '03

23 Nov '03

Bug/Patch Summary ----------------- 574 open / 4359 total bugs (+43) 193 open / 2459 total patches (+11) New Bugs -------- inconsistent popen[2-4]() docs (2003-11-16) http://python.org/sf/843293 help(obj) should use __doc__ when available (2003-11-16) http://python.org/sf/843385 tkFileDialog.Open is broken (2003-11-17) http://python.org/sf/843999 "up" instead of "down" in turtle module documentation (2003-11-17) http://python.org/sf/844123 urllib2 fails its builtin test (2003-11-18) http://python.org/sf/844336 codecs.open().readlines(sizehint) bug (2003-11-18) http://python.org/sf/844561 PackageManager: deselect show hidden: indexerror (2003-11-18) http://python.org/sf/844676 os.exec* and first 'arg' (2003-11-19) http://python.org/sf/845342 imaplib: traceback from _checkquote with empty string (2003-11-19) http://python.org/sf/845560 Python crashes when __init__.py is a directory. (2003-11-20) http://python.org/sf/845802 os.chmod does not work with a unicode filename (2003-11-20) http://python.org/sf/846133 error in python's grammar (2003-11-21) http://python.org/sf/846521 "and" operator tests the first argument twice (2003-11-21) http://python.org/sf/846564 control-c is being sent to child thread rather than main (2003-11-21) http://python.org/sf/846817 email.Parser.Parser doesn't check for valid Content-Type (2003-11-21) http://python.org/sf/846938 datetime.datetime initialization needs more strict checking (2003-11-21) http://python.org/sf/847019 NotImplemented return value misinterpreted in new classes (2003-11-21) http://python.org/sf/847024 textwrap ignoring fix_sentence_endings for single lines (2003-11-22) http://python.org/sf/847346 New Patches ----------- socketmodule.c: fix for platforms w/o IPV6 (i.e.Solaris 5.7) (2003-11-19) http://python.org/sf/845306 Check for signals during regular expression matches (2003-11-20) http://python.org/sf/846388 fix for bug #812325 (tarfile violates bufsize) (2003-11-21) http://python.org/sf/846659 Closed Bugs ----------- IDE Preferences (2002-09-11) http://python.org/sf/607816 Support RFC 2111 in email package (2002-10-21) http://python.org/sf/626452 RFC 2112 in email package (2002-11-06) http://python.org/sf/634412 elisp: IM-python menu and newline in function defs (2003-03-21) http://python.org/sf/707707 Problem With email.MIMEText Package (2003-05-12) http://python.org/sf/736407 test zipimport fails (2003-07-03) http://python.org/sf/765456 IDE defaults to Mac linefeeds (2003-08-04) http://python.org/sf/782686 email bug with message/rfc822 (2003-08-24) http://python.org/sf/794458 email.Message param parsing problem II (2003-08-25) http://python.org/sf/795081 plat-mac/applesingle.py needs cosmetic changes (2003-09-09) http://python.org/sf/803498 _tkinter compilation fails (2003-09-12) http://python.org/sf/805200 RedHat 9 blows up at dlclose of pyexpat.so (2003-09-29) http://python.org/sf/814726 bug with ill-formed rfc822 attachments (2003-09-30) http://python.org/sf/815563 Missing import in email example (2003-10-01) http://python.org/sf/816344 exception with Message.get_filename() (2003-10-15) http://python.org/sf/824417 bad value of INSTSONAME in Makefile (2003-10-15) http://python.org/sf/824565 email/Generator.py: Incorrect header output (2003-10-20) http://python.org/sf/826756 httplib hardcodes Accept-Encoding (2003-10-28) http://python.org/sf/831747 email generator can give bad output (2003-11-04) http://python.org/sf/836293 Bug in type's GC handling causes segfaults (2003-11-10) http://python.org/sf/839548 weakref callbacks and gc corrupt memory (2003-11-12) http://python.org/sf/840829 Windows mis-installs to network drive (2003-11-14) http://python.org/sf/842629 Closed Patches -------------- 755617: better docs for os.chmod (2003-06-16) http://python.org/sf/755677 startup file compiler flags (2003-08-24) http://python.org/sf/794400 Build changes for AIX (2003-11-05) http://python.org/sf/836434 One more patch for --enable-shared (2003-11-13) http://python.org/sf/841807 NameError in the example of sets module (2003-11-15) http://python.org/sf/842994 doc fixes builtin super and string.replace (2003-11-16) http://python.org/sf/843088

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