Mailman 3 March 2003 - Python-Dev

xmlrpclib
by Bill Bumgarner 06 Mar '03

06 Mar '03

Is there active work on the xmlrpclib module these days? The HTTPTransport patch/addition should likely go out with 2.3 as it adds easy authentication and proxy support to xmlrpclib. Also, the unicode support in xmlrpclib is broken in that it can't handle subclasses of <type 'unicode'>. b.bum

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httplib SSLFile broken in CVS
by Kevin Jacobs 06 Mar '03

06 Mar '03

Hi all, SourceForge isn't letting me in, so I'm dropping a note here to report that Raymond Hettinger's changes to httplib.py (Rev 1.72 on Wed Feb 26 22:45:18 2003 UTC) have broken the read() method on the SSLFile object. I suspect that he was trying to be clever by adding iterators to code that worked just fine (if not better) without them. Unfortunately, clever code has to be tested. The diff below repairs it, though I'd be just as happy if that part of Rev 1.72 was reverted. --- httplib.py.orig 2003-03-05 19:37:28.000000000 -0500 +++ httplib.py 2003-03-06 10:11:01.000000000 -0500 @@ -864,13 +864,15 @@ def read(self, size=None): L = [self._buf] + self._buf = '' if size is None: - self._buf = '' for s in iter(self._read, ""): L.append(s) - return "".join(L) else: - avail = len(self._buf) + avail = len(L[0]) + if avail >= size: + self._buf = L[0][size:] + return L[0][:size] for s in iter(self._read, ""): L.append(s) avail += len(s) @@ -878,14 +880,19 @@ all = "".join(L) self._buf = all[size:] return all[:size] + return "".join(L) def readline(self): L = [self._buf] self._buf = '' + i = L[0].find("\n") + 1 + if i > 0: + self._buf = L[0][i:] + return L[0][:i] for s in iter(self._read, ""): L.append(s) - if "\n" in s: - i = s.find("\n") + 1 + i = s.find("\n") + 1 + if i > 0: self._buf = s[i:] L[-1] = s[:i] break Regards, -Kevin -- -- Kevin Jacobs The OPAL Group - Enterprise Systems Architect Voice: (216) 986-0710 x 19 E-mail: jacobs(a)theopalgroup.com Fax: (216) 986-0714 WWW: http://www.theopalgroup.com

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More Zen
by Raymond Hettinger 06 Mar '03

06 Mar '03

Iterators unified access to containers -- lets find more of those. Substitutability simplifies development so shelves have a full dictionary interface but tuples won't sprout a count method because lists differ in intent. Deprecation comes at a price but cruft has a cost of its own. Holistic refactoring beats piecemeal optimization. Comment generously, the best modules are an education to read. Be kind on the Usenet some posters are only eleven. Raymond Hettinger

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Pferdemarkt.ws informiert! Newsletter 03/2003 http://www.pferdemarkt.ws
by webmaster＠pferdemarkt.ws 06 Mar '03

06 Mar '03

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Re: More Zen
by Chermside, Michael 06 Mar '03

06 Mar '03

Raymond: I particularly like your last zen point: > Be kind on the Usenet some posters are only eleven. I like it for two reasons... one, being that it's an important truth (as recently illustrated ;-)), but secondly that it reminds us that Python is more than a language... it also includes a very strong and helpful community without which all the design principles in the world would never lead to such a successful language. -- Michael Chermside

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Pre-PyCon sprint ideas
by Brett Cannon 06 Mar '03

06 Mar '03

In an effort to help Guido (did you get my email about the rough draft of the email to send out to the rest of the world?) I am trying to gather ideas for what the Python core sprint can focus on. I have set up a wiki page at http://www.python.org/cgi-bin/moinmoin/PyCoreSprint for people to add ideas to. If there is something you think deserves sprint attention then go add it. -Brett

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Fun with timeit.py
by Guido van Rossum 06 Mar '03

06 Mar '03

At Jim's request, I added a utility module to the standard library that implements state-of-the-art timing of code snippets. Using a slightly modified version of this code, here's the cost in microseconds of one for loop iteration (with 'pass' as the loop body) in various Python versions. All tests were run on my home machine: a 664 MHz Pentium III with 256 KB cache, running Red Hat Linux 7.3, compiled with gcc 2.96. Note the steady improvement over the years. :-) version plain -O ------- ----- ----- 1.3 0.625 n/a 1.4 0.602 n/a 1.5.2 0.606 0.466 2.0 0.561 0.445 2.1 0.591 0.436 2.2 0.416 0.277 2.3a2+ 0.246 0.248 (1) The invocation was "python timeit.py -r5" (with -O added for the last column). This times 5 runs of a million iterations each and prints the time (normalized to usec per iteration) for the fastest run. I ran this twice for each combination and picked the lowest of the two; there was never more than 0.002 usec difference. (1) A mystery: the Python 2.3 binary installed in /usr/local/bin measured 0.266 for the -O case, but 0.248 without -O; i.e. -O made it slower! The byte-for-byte identical binary in my build tree produced the more reasonable measurements given in the table. --Guido van Rossum (home page: http://www.python.org/~guido/)

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JUMP_IF_X opcodes
by Damien Morton 04 Mar '03

04 Mar '03

I have been reviewing the compile.c module with respect to the use of JUMP_IF_XXX opcodes, and the frequency with which these opcodes are followed by a POP_TOP instruction. It seems to me that there are two kinds of uses cases for these opcodes, The first use case could be expressed as POP_THEN_JUMP_IF_XXXX The second use case could be expressed as JUMP_IF_XXX_ELSE_POP Listed below are the use cases for these instructions, and the functions in compile.c that they apear in. The form is JUMP_IF_XXX(top-of-stack-if-no-jump, top-of-stack-if-jump) com_assert_stmt - JUMP_IF_TRUE(-,-) com_if_stmt - JUMP_IF_FALSE(-,-) com_while_stmt - JUMP_IF_FALSE(-,-) com_try_except - JUMP_IF_FALSE(-,-) com_list_if - JUMP_IF_FALSE(-, -) com_comparison - JUMP_IF_FALSE(-, 0) com_and_test - JUMP_IF_FALSE(-, 0) com_test - JUMP_IF_TRUE(-, 1) Below is a minimally intrusive implementation of the expansion of JUMP_IF_FALSE into two opcodes for handling the two use cases. case JUMP_IF_FALSE_ELSE_POP: case POP_THEN_JUMP_IF_FALSE: NEXTARG(oparg); err = PyObject_IsTrue(TOP()); if (err > 0) { err = 0; POP(); } else if (err == 0) { if (opcode == POP_THEN_JUMP_IF_FALSE) POP(); JUMPBY(oparg); } else break; continue; Comments, suggestions, etc, appreciated.

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__slots__ for metatypes
by Christian Tismer 04 Mar '03

04 Mar '03

Hi Guido, all, last year, I wrote a patch that allows meta-types to have slots. You had no time to look into it, and I said "take your time and wait until it is stable". I have been using this for quite a while now, and today I updated it for Python 2.3 . The patch is very small and simple. Essentially, it doesn't use a fixed offset into the internal etype structure, but computed this based upon tp_basicsize. This small patch also gives lots of flexibility to people, who like to add extra stuff to their dynamic type objects. (Well, I do this frequently) It would be nice if we could add this small feature, soon. http://www.python.org/sf/696193 Due to some SF bug, I had to submit this patch twice. thanks a lot - chris -- Christian Tismer :^) <mailto:tismer@tismer.com> Mission Impossible 5oftware : Have a break! Take a ride on Python's Johannes-Niemeyer-Weg 9a : *Starship* http://starship.python.net/ 14109 Berlin : PGP key -> http://wwwkeys.pgp.net/ work +49 30 89 09 53 34 home +49 30 802 86 56 pager +49 173 24 18 776 PGP 0x57F3BF04 9064 F4E1 D754 C2FF 1619 305B C09C 5A3B 57F3 BF04 whom do you want to sponsor today? http://www.stackless.com/

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new bytecode results
by Damien Morton 03 Mar '03

03 Mar '03

I tried adding a variety of new instructions to the PVM, initially with a code compression goal for the bytecodes, and later with a performance goal. definitions: USING_LOAD_FAST_N accesses to locals with an index<16 using a one byte instruction (no oparg) USING_LOAD_CONST_N accesses to consts with an index<16 using a one byte instruction (no oparg) USING_STORE_FAST_N accesses to locals with an index<16 using a one byte instruction (no oparg) USING_SHORT_CMP compare ops using a one byte instruction (no oparg) PyStone score for best of 10 runs. umodified 2.3a2 22200 using enum, 22200 (compacting the opcode numeric space using an enum instead of #defines) USING_LOAD_FAST_N 22700 USING_LOAD_CONST_N 22400 USING_STORE_FAST_N 22400 USING_LOAD_FAST_N, USING_LOAD_CONST_N 22350 USING_LOAD_FAST_N, USING_STORE_FAST_N, 22000 USING_LOAD_FAST_N, USING_LOAD_CONST_N, USING_STORE_FAST_N 22200 USING_SHORT_CMP 21500 USING_LOAD_FAST_N, USING_LOAD_CONST_N, USING_STORE_FAST_N, USING_SHORT_CMP 22000 Conclusions: While reducing the size of compiled bytecodes by about 1%, the proposed modifications at best increase performance by 2%, and at worst reduce performance by 3%. Enabling all of the proposed opcodes results in a 1% performance loss. In general, it would seem that adding opcodes in bulk, even if many opcodes switch to the same labels, results in a minor performance loss. Running PyStone under windows results in a fairly large variation in results. A zip file containing the source files I modified can be found at http://www.bitfurnace.com/python/modified-source.zip. If someone would like to try this code on their systems, I would be grateful to know what kind of results they achieve. The various proposed opcodes are controlled by a set of #defines in the file opcode.h Next steps: The results of my static analysis indicate that the indices used on LOAD_FAST, LOAD_CONST, STORE_FAST are almost always small. There may be some benefit to optimising these instructions to use single byte opargs. The results of my static and dynamic analysis indicate that the (COMPARE_OP, JUMP_IF_FALSE, POP_TOP) pattern is highly used. Im looking at what changes would need to be made to the compiler to remove the need for this sequence of instructions.

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