Re: [Python-Dev] test_ctypes failure on Mac OS X/PowerPC 10.3.9 (Panther)
Ronald Oussoren schrieb: > > On 20-jun-2006, at 20:50, Ronald Oussoren wrote: > >> >> On 20-jun-2006, at 20:06, Thomas Heller wrote: >> >>> Trent Mick schrieb: Thomas and others, Has anyone else seen failures in test_ctypes on older Mac OS X/ PowerPC? Results are below. This is running a build of the trunk from last night: ./configure && make && ./python.exe Lib/test/test_ctypes.py Note that the test does NOT fail on the Mac OS X/x86 10.4.6 box that I have. >>> >>> It also works on 10.4.?? Power PC. I guess the fix has to wait until >>> I'm able to install 10.3 on my mac, I have the DVDs already but >>> have not >>> yet had the time. If anyone is willing to give me ssh access to a >>> 10.3 >>> box I can try to fix this earlier. >> >> I had some problems with my 10.3-capable box, but happily enough it >> decided to come alive again. I'm currently booted into 10.3.9 and >> will have a look. > > It is a platform bug, RTLD_LOCAL doesn't work on 10.3. The following C > snippet fails with the same error as ctypes: FAIL: dlcompat: unable to > open this file with RTLD_LOCAL. This seems to be confirmed by this > sourcet test file from darwin: > http://darwinsource.opendarwin.org/10.4.1/dyld-43/unit-tests/test-cases/dlopen-RTLD_LOCAL/main.c. > > What does this mean? Would it work with RTLD_GLOBAL, is there any other way to repair it, or does loading dylibs not work at all on Panther? Thomas ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] test_ctypes failure on Mac OS X/PowerPC 10.3.9(Panther)
On Wednesday, June 21, 2006, at 09:43AM, Thomas Heller <[EMAIL PROTECTED]> wrote: >Ronald Oussoren schrieb: >>> will have a look. >> >> It is a platform bug, RTLD_LOCAL doesn't work on 10.3. The following C >> snippet fails with the same error as ctypes: FAIL: dlcompat: unable to >> open this file with RTLD_LOCAL. This seems to be confirmed by this >> sourcet test file from darwin: >> http://darwinsource.opendarwin.org/10.4.1/dyld-43/unit-tests/test-cases/dlopen-RTLD_LOCAL/main.c. >> >> > >What does this mean? Would it work with RTLD_GLOBAL, is there any other >way to repair it, or does loading dylibs not work at all on Panther? Using RTLD_GLOBAL does work. This should also be fairly save as RTLD_GLOBAL seems to be the same as RTLD_LOCAL when using two-level namespaces (which is the default on OSX and used by Python). Ronald ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On Wed, 21 Jun 2006, Phillip J. Eby wrote: > Well, EIBTI and all that: > > switch x: > case == 1: foo(x) > case in S: bar(x) > > It even lines up nicely. :) Hmm, this is rather nice. I can imagine possible use cases for switch x: case > 3: foo(x) case is y: spam(x) case == z: eggs(x) An interesting use case for which this offers no corresponding syntax is case instanceof ClassA: ham(x) which doesn't work because Python spells a type test as isinstance(a, b) rather than with an operator. (I suppose whether we want it to be an operator might be another question to think about for Python 3000.) -- ?!ng ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Ka-Ping Yee wrote: > On Wed, 21 Jun 2006, Phillip J. Eby wrote: >> Well, EIBTI and all that: >> >> switch x: >> case == 1: foo(x) >> case in S: bar(x) >> >> It even lines up nicely. :) > > Hmm, this is rather nice. I can imagine possible use cases for > > switch x: > case > 3: foo(x) > case is y: spam(x) Ha, a slight reminiscence of BASIC... > case == z: eggs(x) > > An interesting use case for which this offers no corresponding > syntax is > > case instanceof ClassA: ham(x) > > which doesn't work because Python spells a type test as > isinstance(a, b) rather than with an operator. (I suppose > whether we want it to be an operator might be another > question to think about for Python 3000.) FWIW, I like "is a" most, but there's no way to spell this as one word without confusing readers. Georg ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Greg Ewing wrote: > Phillip J. Eby wrote: > >> Actually, one could consider "case" expressions to be computed at function >> definition time, the way function defaults are. That would solve the >> problem of symbolic constants, or indeed any sort of expressions. > > That's an excellent idea! > >> It's just a question of which one is easier to explain. > > I think the function-definition-time one is easiest to > both explain and also to reason about when writing code, > since definition time is well-defined, whereas "the first > time it's executed" is somewhat fuzzy. There's some benefit to "first time it's executed" though: a. it allows access to the local namespace b. it uses the same semantics at module level as it does in a function If we go with 'at function definition time', then neither of those is true. I'm actually curious how a module level switch statement would work at all in that case, without either falling back on the "first time it's executed" definition, or else not permitting switch statements in module level code. Cheers, Nick. -- Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia --- http://www.boredomandlaziness.org ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
Facundo Batista wrote: > 2006/6/20, Nick Coghlan <[EMAIL PROTECTED]>: >> The intent was always to replace the internal use of tuples and longs >> with a >> more efficient C implementation - that particular step simply wasn't >> needed >> for the original use case that lead Facundo to write and implement PEP >> 327. > > Right. We never addressed speed. I mean, we made Decimal as fast as we > could in the limited time we had (Raymond H. helped a lot also here), > but it was NOT designed for speed. As I recall, the design flow was pretty much 'make it work to spec' then 'make it run the telco benchmark and the tests faster while still keeping the implementation reasonably simple'. Helping Raymond with that tuning process was actually my first real contribution to CPython, so I got a lot of reading done while waiting for the benchmark and the decimal arithmetic tests to run with the Python profiler enabled ;) Even then, I believe only two particularly significant changes were made to the implementation - adding the boolean flag so special values could be detected easily, and copping the conversion costs to & from longs for coefficient arithmetic, because we made the time back in the long run by getting to use the C-coded long arithmetic operations. > BTW, prove me Decimal is not fast enough, ;) C:\Python24>python -m timeit -s "x = 1.0" "x+x" 1000 loops, best of 3: 0.137 usec per loop C:\Python24>python -m timeit -s "from decimal import Decimal as d; x = d(1)" "x+x" 1 loops, best of 3: 48.3 usec per loop I don't really know my definition of 'fast enough to be the basic floating point type', but I'm pretty sure that a couple of orders of magnitude slower isn't it. I guess I'll find out what my definition is if the C implementation manages to get there ;) (Hmm - a couple of spot checks makes it look like the decimal module's slowed down by a few percent in Python 2.5. It's probably worth trying out the new profiler on the module to see if there are any simple fixes to be made before beta 2. . .) Cheers, Nick. -- Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia --- http://www.boredomandlaziness.org ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 03:38 AM 6/21/2006 -0500, Ka-Ping Yee wrote: >On Wed, 21 Jun 2006, Phillip J. Eby wrote: > > Well, EIBTI and all that: > > > > switch x: > > case == 1: foo(x) > > case in S: bar(x) > > > > It even lines up nicely. :) > >Hmm, this is rather nice. I can imagine possible use cases for > > switch x: > case > 3: foo(x) > case is y: spam(x) > case == z: eggs(x) > >An interesting use case for which this offers no corresponding >syntax is > > case instanceof ClassA: ham(x) Actually, I was assuming that any other operator besides == and 'in' would be relegated to an if-elif chain in the default case, although it's almost possible to do that automatically, I suppose. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
On Wed, Jun 21, 2006, Nick Coghlan wrote: > Facundo Batista wrote: >> >> BTW, prove me Decimal is not fast enough, ;) > > C:\Python24>python -m timeit -s "x = 1.0" "x+x" > 1000 loops, best of 3: 0.137 usec per loop > > C:\Python24>python -m timeit -s "from decimal import Decimal as d; x = d(1)" > "x+x" > 1 loops, best of 3: 48.3 usec per loop > > I don't really know my definition of 'fast enough to be the basic > floating point type', but I'm pretty sure that a couple of orders of > magnitude slower isn't it. I guess I'll find out what my definition is > if the C implementation manages to get there ;) Why isn't that fast enough? Relative speed is *not* the issue when talking about real-world applications. More to the point, the expectation is that the C implementation of Decimal will have faster conversion to/from string, which in many real world applications forms a significant part of the processing load. -- Aahz ([EMAIL PROTECTED]) <*> http://www.pythoncraft.com/ "I saw `cout' being shifted "Hello world" times to the left and stopped right there." --Steve Gonedes ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
Nick Coghlan wrote: >> BTW, prove me Decimal is not fast enough, ;) > > C:\Python24>python -m timeit -s "x = 1.0" "x+x" > 1000 loops, best of 3: 0.137 usec per loop > > C:\Python24>python -m timeit -s "from decimal import Decimal as d; x = d(1)" > "x+x" > 1 loops, best of 3: 48.3 usec per loop > > I don't really know my definition of 'fast enough to be the basic floating > point type', but I'm pretty sure that a couple of orders of magnitude slower > isn't it. how fast does the corresponding C program run ? ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
On 6/21/06, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > Nick Coghlan wrote: > > >> BTW, prove me Decimal is not fast enough, ;) > > > > C:\Python24>python -m timeit -s "x = 1.0" "x+x" > > 1000 loops, best of 3: 0.137 usec per loop > > > > C:\Python24>python -m timeit -s "from decimal import Decimal as d; x = > > d(1)" "x+x" > > 1 loops, best of 3: 48.3 usec per loop > > > > I don't really know my definition of 'fast enough to be the basic floating > > point type', but I'm pretty sure that a couple of orders of magnitude slower > > isn't it. > > how fast does the corresponding C program run ? A horribly crude test using Regina Rexx (which implements the Decimal standard in C, but I know nothing else about how): x = 1.0 do 1000 y = x + x end This takes about 5 sec on my PC, which (if I've calculated correctly) comes out at 0.5 usec per loop. I suppose it gives a ballpark figure for the sorts of speeds we can expect from a C implementation. Paul. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Nick Coghlan <[EMAIL PROTECTED]> wrote: > There's some benefit to "first time it's executed" though: >a. it allows access to the local namespace And how would that be a good thing? It just begs for confusion if the local variable doesn't always have the same value. (Yes, globals may vary too, but less likely, since global *variables* (i.e. that actually vary) are generally considered a bad idea. There's no such taboo for local variables. :-) >b. it uses the same semantics at module level as it does in a function Hm, I hadn't thought of that one yet. > If we go with 'at function definition time', then neither of those is true. > I'm actually curious how a module level switch statement would work at all in > that case, without either falling back on the "first time it's executed" > definition, or else not permitting switch statements in module level code. After thinking about it a bit I think that if it's not immediately contained in a function, it should be implemented as alternative syntax for an if/elif chain. -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 03:38 AM 6/21/2006 -0500, Ka-Ping Yee wrote: > >On Wed, 21 Jun 2006, Phillip J. Eby wrote: > > > Well, EIBTI and all that: > > > > > > switch x: > > > case == 1: foo(x) > > > case in S: bar(x) > > > > > > It even lines up nicely. :) > > > >Hmm, this is rather nice. I can imagine possible use cases for > > > > switch x: > > case > 3: foo(x) > > case is y: spam(x) > > case == z: eggs(x) > > > >An interesting use case for which this offers no corresponding > >syntax is > > > > case instanceof ClassA: ham(x) > > Actually, I was assuming that any other operator besides == and 'in' would > be relegated to an if-elif chain in the default case, although it's almost > possible to do that automatically, I suppose. I've been thinking about generalization to other operators too, but decided that it would be a mistake. It would be quite clumsy to explain the exact semantics: if all operators are "==" or "in" an efficient hash table gets pre-constructed at function definition time, otherwise, um..., what exactly? (Note how I've switched to the switch-for-efficiency camp, since it seems better to have clear semantics and a clear reason for the syntax to be different from if/elif chains.) -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] RELEASED Python 2.5 (beta 1)
On behalf of the Python development team and the Python community, I'm happy to announce the first BETA release of Python 2.5. This is an *beta* release of Python 2.5. As such, it is not suitable for a production environment. It is being released to solicit feedback and hopefully discover bugs, as well as allowing you to determine how changes in 2.5 might impact you. If you find things broken or incorrect, please log a bug on Sourceforge. I'd like to really encourage you to try out this version and check that your code still works - if not, and you think it's a bug, please log a bug. Hopefully this will make it easier for you to upgrade once the final release of Python 2.5 is done. Please note that changes to improve Python's support for 64 bit systems might require authors of C extensions to change their code. See the website for more, including a link to a posting discussing this issue in particular. More information on the release (as well as source distributions and Windows and Mac OSX installers) are available from the 2.5 website: http://www.python.org/2.5/ Since the alpha releases, a slew of bug fixes and smaller new features have been added. See the release notes (available from the 2.5 webpage) for more. The first beta also includes the results of the Iceland NeedForSpeed sprint, resulting in some significant speedups. As of this release, Python 2.5 is now in *feature freeze*. No new features are planned - only bugfixes for the code already in the codebase. The plan from here is for one more beta release followed by one or more release candidates as needed, leading to a 2.5 final release early August. PEP 356 includes the schedule and will be updated as the schedule evolves. The new features in Python 2.5 are described in Andrew Kuchling's What's New In Python 2.5. It's available from the 2.5 web page. Amongst the language features added include conditional expressions, the with statement, the merge of try/except and try/finally into try/except/finally, enhancements to generators to produce a coroutine kind of functionality, and a brand new AST-based compiler implementation. New modules added include hashlib, ElementTree, sqlite3, wsgiref and ctypes. We also have a new profiling module "cProfile". Enjoy this new release (another step on the path to Python 2.5 final) Anthony -- Anthony Baxter [EMAIL PROTECTED] Python Release Manager (on behalf of the entire python-dev team) pgpxpkNRaGBAW.pgp Description: PGP signature ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 09:16 AM 6/21/2006 -0700, Guido van Rossum wrote: >After thinking about it a bit I think that if it's not immediately >contained in a function, it should be implemented as alternative >syntax for an if/elif chain. That worries me a little. Suppose I write a one-off script like this: for line in sys.stdin: words = line.split() if words: switch words[0]: case "foo": blah case words[-1]: print "mirror image!" Then, if I later move the switch into a function, it's not going to mean the same thing any more. If the values are frozen at first use or definition time (which are the same thing for module-level code), then I'll find the lurking bug sooner. OTOH, breaking it sooner doesn't seem like such a great idea either; seems like a recipe for a newbie-FAQ, actually. ISTM that the only sane way to deal with this would be to ban the switch statement at module level, which then seems to be an argument for not including the switch statement at all. :( I suppose the other possibility would be to require at compilation time that a case expression include only non-local variables. That would mean that you couldn't use *any* variables in a case expression at module-level switch, but wording the error message for that to not be misleading might be tricky. I suppose an error message for the above could simply point to the fact that 'words' is being rebound in the current scope, and thus can't be considered a constant. This is only an error at the top-level if the switch appears in a loop, and the variable is rebound somewhere within that loop or is rebound more than once in the module as a whole (including 'global' assignments in functions). ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] TRUNK is UNFROZEN, but in FEATURE FREEZE
2.5b1 is out, so I'm declaring the SVN trunk unfrozen. Note, though, that as we're now post-beta, we're in FEATURE FREEZE. Really. This means you. :-) No new features should be checked in without prior approval - checkins that violate this will quite probably get backed out. I expect that we will also now be quite a bit more anal about any checkins that break the buildbots. Please, please make sure you run the test suite before checking in - and if you're at all concerned that your checkin might have strange platform dependencies, check the buildbot status page (http://www.python.org/dev/buildbot/trunk/) after your checkin to make sure it didn't break anything. Similarly, if you're fixing a bug, if at all possible write a test and check that in as well. The buildbots and a focus on testing should mean that 2.5 ends up being one of the most solid Python releases so far. Please help us achieve this goal. The feature freeze on the trunk will continue until we branch for release candidate 1 of 2.5 - sometime in the second half of July, probably. If you really have the need to do new work on the trunk before then, please work on a branch. Thanks, Anthony -- Anthony Baxter <[EMAIL PROTECTED]> It's never too late to have a happy childhood. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Guido van Rossum wrote: > (Note how I've switched to the switch-for-efficiency camp, since it > seems better to have clear semantics and a clear reason for the syntax > to be different from if/elif chains.) if you're now in the efficiency camp, why not just solve this on the code generator level ? given var = some expression if var == constant: ... elif var == constant: ... let the compiler use a dispatch table, if it can and wants to. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > Guido van Rossum wrote: > > > (Note how I've switched to the switch-for-efficiency camp, since it > > seems better to have clear semantics and a clear reason for the syntax > > to be different from if/elif chains.) > > if you're now in the efficiency camp, why not just solve this on the > code generator level ? given > > var = some expression > if var == constant: > ... > elif var == constant: > ... > > let the compiler use a dispatch table, if it can and wants to. But in most cases the 'constant' is actually an expression involving a global, often even a global in another module. (E.g. sre_compile.py) The compiler will have a hard time proving that this is really a constant, so it won't optimize the code. The proposed switch semantics (create the table when the containing function is defined) get around this by "defining" what it means by "constant". BTW I would like references to locals shadowing globals to be flagged as errors (or at least warnings) so that users who deduced the wrong mental model for a switch statement are caught out sooner. -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 09:16 AM 6/21/2006 -0700, Guido van Rossum wrote: > >After thinking about it a bit I think that if it's not immediately > >contained in a function, it should be implemented as alternative > >syntax for an if/elif chain. > > That worries me a little. Suppose I write a one-off script like this: > > for line in sys.stdin: > words = line.split() > if words: > switch words[0]: > case "foo": blah > case words[-1]: print "mirror image!" Why would you write a script like that? If you've learned the "idiomatic" use of a switch statement first, that would never occur to you. If you're totally clueless, I don't really care that much. > Then, if I later move the switch into a function, it's not going to mean > the same thing any more. And it will be a clear compile-time warning because in the refactored version you'd be attempting to use a local variable in a case. > If the values are frozen at first use or > definition time (which are the same thing for module-level code), then I'll > find the lurking bug sooner. Or not, depending on how easily the misbehavior is spotted from a cursory glance at the output. > OTOH, breaking it sooner doesn't seem like such a great idea either; seems > like a recipe for a newbie-FAQ, actually. ISTM that the only sane way to > deal with this would be to ban the switch statement at module level, which > then seems to be an argument for not including the switch statement at all. > :( I don't understand this line of reasoning. The semantics I propose are totally well-defined. > I suppose the other possibility would be to require at compilation time > that a case expression include only non-local variables. That would mean > that you couldn't use *any* variables in a case expression at module-level > switch, but wording the error message for that to not be misleading might > be tricky. That seems overly restrictive given that I expect *most* cases to use named constants, not literals. > I suppose an error message for the above could simply point to the fact > that 'words' is being rebound in the current scope, and thus can't be > considered a constant. This is only an error at the top-level if the > switch appears in a loop, and the variable is rebound somewhere within that > loop or is rebound more than once in the module as a whole (including > 'global' assignments in functions). Let's not focus on the error message. I think your assumption that every switch at the global level ought to be able to be moved into a function and work the same way is not a particularly important requirement. (As a compromise, a switch at the global level with only literal cases could be efficiently optimized. This should include "compile-time constant expressions".) BTW a switch in a class should be treated the same as a global switch. But what about a switch in a class in a function? -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 06:41 PM 6/21/2006 +0200, Fredrik Lundh wrote: >Guido van Rossum wrote: > > > (Note how I've switched to the switch-for-efficiency camp, since it > > seems better to have clear semantics and a clear reason for the syntax > > to be different from if/elif chains.) > >if you're now in the efficiency camp, why not just solve this on the >code generator level ? given > > var = some expression > if var == constant: > ... > elif var == constant: > ... > >let the compiler use a dispatch table, if it can and wants to. Two reasons: 1. Having special syntax is an assertion that 'var' will be usable as a dictionary key. Without this assertion, the generated code would need to trap hashing failure. 2. Having special syntax is likewise an assertion that the 'constants' will remain constant, if they're symbolic constants like: FOO = "foo" ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 09:55 AM 6/21/2006 -0700, Guido van Rossum wrote: >BTW a switch in a class should be treated the same as a global switch. >But what about a switch in a class in a function? Okay, now my head hurts. :) A switch in a class doesn't need to be treated the same as a global switch, because locals()!=globals() in that case. I think the top-level is the only thing that really needs a special case vs. the general "error if you use a local variable in the expression" rule. Actually, it might be simpler just to always reject local variables -- even at the top-level -- and be done with it. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 09:55 AM 6/21/2006 -0700, Guido van Rossum wrote: > >BTW a switch in a class should be treated the same as a global switch. > >But what about a switch in a class in a function? > > Okay, now my head hurts. :) Welcome to the club. There's a Monty Python sketch appropriate... > A switch in a class doesn't need to be treated the same as a global switch, > because locals()!=globals() in that case. But that's not the discerning rule in my mind; the rule is, how to define "at function definition time". > I think the top-level is the only thing that really needs a special case > vs. the general "error if you use a local variable in the expression" rule. To the contrary, at the top level my preferred semantics don't care because they don't use a hash. The strict rules about locals apply when it occurs inside a function, since then we eval the case expressions at function definition time, when the locals are undefined. This would normally be good enough, but I worry (a bit) about this case: y = 12 def foo(x, y): switch x: case y: print "something" which to the untrained observer (I care about untrained readers much more than about untrained writers!) looks like it would print something if x equals y, the argument, while in fact it prints something if x equals 12. > Actually, it might be simpler just to always reject local variables -- even > at the top-level -- and be done with it. Can't because locals at the top-level are also globals. -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Guido van Rossum wrote: > But in most cases the 'constant' is actually an expression involving a > global, often even a global in another module. (E.g. sre_compile.py) > The compiler will have a hard time proving that this is really a > constant, so it won't optimize the code. unless we come up with a way to make it possible to mark an variable as a constant. > The proposed switch semantics (create the table when the containing > function is defined) get around this by "defining" what it means by > "constant". well, given that people find it really confusing that the two X:es in def func(value=X): print X are evaluated at different times, I'm not sure it's a good idea to introduce more "evaluation scopes". but sure, I'm sure people doing certification tests would love questions like: Q: If a program calls the 'func' function below as 'func()' and ONE and TWO are both integer objects, what does 'func' print ? ONE = 1 TWO = 2 def func(value=ONE): switch value: case ONE: print value, "is", ONE case TWO: print value, "is", TWO a: "1 is 1" b: "2 is 2" c: nothing at all d: either "1 is 1" or nothing at all e: who knows ? but I cannot say I find it especially Pythonic, really... ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 10:27 AM 6/21/2006 -0700, Guido van Rossum wrote: >On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > > At 09:55 AM 6/21/2006 -0700, Guido van Rossum wrote: > > >BTW a switch in a class should be treated the same as a global switch. > > >But what about a switch in a class in a function? > > > > Okay, now my head hurts. :) > >Welcome to the club. There's a Monty Python sketch appropriate... Aha! So *that's* why Jim Fulton is always going "W". :) > > A switch in a class doesn't need to be treated the same as a global switch, > > because locals()!=globals() in that case. > >But that's not the discerning rule in my mind; the rule is, how to >define "at function definition time". Wa! (i.e., my head hurts again :) > > I think the top-level is the only thing that really needs a special case > > vs. the general "error if you use a local variable in the expression" rule. > >To the contrary, at the top level my preferred semantics don't care >because they don't use a hash. > >The strict rules about locals apply when it occurs inside a function, >since then we eval the case expressions at function definition time, >when the locals are undefined. This would normally be good enough, but >I worry (a bit) about this case: > > y = 12 > def foo(x, y): > switch x: > case y: print "something" > >which to the untrained observer (I care about untrained readers much >more than about untrained writers!) looks like it would print >something if x equals y, the argument, while in fact it prints >something if x equals 12. I was thinking this should be rejected due to a local being in the 'case' expression. > > Actually, it might be simpler just to always reject local variables -- even > > at the top-level -- and be done with it. > >Can't because locals at the top-level are also globals. But you could also just use literals, and the behavior would then be consistent. But I'm neither so enamored of that solution nor so against if/elif behavior that I care to argue further. One minor point, though: what happens if we generate an if/elif for the switch, and there's a repeated case value? The advantage of still using the hash-based code at the top level is that you still get an error for duplicating keys. Ugh. It still seems like the simplest implementation is to say that the lookup table is built "at first use" and that the case expressions may not refer to variables that are known to be bound in the current scope, or rebound in the case of the top level. So the 'case y' example would be a compile-time error, as would my silly "words" example. But code that only used "constants" at the top level would work. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Fredrik Lundh wrote: >> But in most cases the 'constant' is actually an expression involving a >> global, often even a global in another module. (E.g. sre_compile.py) >> The compiler will have a hard time proving that this is really a >> constant, so it won't optimize the code. > > unless we come up with a way to make it possible to mark an variable as > a constant. such as the primary 'constant' expr which simply means that expr will be evaluated at function definition time, rather than at runtime. example usage: var = expression if var == constant sre.FOO: ... elif var == constant sre.BAR: ... elif var in constant (sre.FIE, sre.FUM): ... ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > >But that's not the discerning rule in my mind; the rule is, how to > >define "at function definition time". > > Wa! (i.e., my head hurts again :) Um, wasn't this your proposal (to freeze the case expressions at function definition time)? > > > I think the top-level is the only thing that really needs a special case > > > vs. the general "error if you use a local variable in the expression" > > > rule. > > > >To the contrary, at the top level my preferred semantics don't care > >because they don't use a hash. > > > >The strict rules about locals apply when it occurs inside a function, > >since then we eval the case expressions at function definition time, > >when the locals are undefined. This would normally be good enough, but > >I worry (a bit) about this case: > > > > y = 12 > > def foo(x, y): > > switch x: > > case y: print "something" > > > >which to the untrained observer (I care about untrained readers much > >more than about untrained writers!) looks like it would print > >something if x equals y, the argument, while in fact it prints > >something if x equals 12. > > I was thinking this should be rejected due to a local being in the 'case' > expression. Me too. I guess I was just pointing out that "just" evaluating it in the global scope would not give an error, just like this is valid (but confusing): y = 12 def foo(y=y): print y y = 13 foo() # prints 12 > > > Actually, it might be simpler just to always reject local variables -- > > > even > > > at the top-level -- and be done with it. > > > >Can't because locals at the top-level are also globals. > > But you could also just use literals, and the behavior would then be > consistent. But I'm neither so enamored of that solution nor so against > if/elif behavior that I care to argue further. Yeah, but if you have names for your constants it would be a shame if you couldn't use them because they happen to be defined in the same scope. > One minor point, though: what happens if we generate an if/elif for the > switch, and there's a repeated case value? The advantage of still using > the hash-based code at the top level is that you still get an error for > duplicating keys. Sure. But the downside is that it's now actually *slower* than the if/elif version, because it must evaluate all the case expressions. > Ugh. It still seems like the simplest implementation is to say that the > lookup table is built "at first use" and that the case expressions may not > refer to variables that are known to be bound in the current scope, or > rebound in the case of the top level. So the 'case y' example would be a > compile-time error, as would my silly "words" example. But code that only > used "constants" at the top level would work. I don't like "first use" because it seems to invite tricks. The 'case y' example can be flagged as a compile time error with enough compile-time analysis (we *know* all the locals after all). IMO your silly words example should just pass (at the global level); it's silly but not evil, and it's totally clear what it does if it does anything at all (using the if/elif translation semantics; not using the first-use semantics). That it doesn't refactor cleanly into a function body isn't enough reason to forbid it. I feel some kind of rule of thumb coming up regarding language design, but I'm having a hard time saying it clearly. It's something about making commonly written idioms easy to understand even for people without a full understanding of the language, so that (a) people generalizing from a few examples without too much help or prior understanding won't go too far off, and (b) people who *do* care to read and understand the language spec can always clearly find out wat any particular thing means and know the pitfalls. An example is assignment. Python lets you do things like x = 42 y = x and it all sounds completely reasonable. But Fortran/C/C++ programmers beware, although the syntax is familiar, this is really a name-binding statement, not a value-copying statement. There are many other examples. Function and class definition for example (look like definitions but are run-time constructs unlike in most other languages). Etc. -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
On 6/21/06, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > Fredrik Lundh wrote: > > >> But in most cases the 'constant' is actually an expression involving a > >> global, often even a global in another module. (E.g. sre_compile.py) > >> The compiler will have a hard time proving that this is really a > >> constant, so it won't optimize the code. > > > > unless we come up with a way to make it possible to mark an variable as > > a constant. > > such as the primary > > 'constant' expr > > which simply means that expr will be evaluated at function definition > time, rather than at runtime. example usage: > > var = expression > if var == constant sre.FOO: > ... > elif var == constant sre.BAR: > ... > elif var in constant (sre.FIE, sre.FUM): > ... This gets pretty repetitive. One might suggest that 'case' could imply 'constant'...? -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
At 01:16 PM 6/21/2006 -0700, Guido van Rossum wrote: >On 6/21/06, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > > >But that's not the discerning rule in my mind; the rule is, how to > > >define "at function definition time". > > > > Wa! (i.e., my head hurts again :) > >Um, wasn't this your proposal (to freeze the case expressions at >function definition time)? Actually, I proposed that either that *or* first use could work, and in subsequent discussion I sided with first use. Greg didn't quote the rest of my original post or any of the subsequent discussion in the post you picked up on, so that probably gave you the impression I was still in favor of function definition time, when I had already begun leaning towards "first use" as easier to define. >Yeah, but if you have names for your constants it would be a shame if >you couldn't use them because they happen to be defined in the same >scope. Maybe the real answer is to have a "const" declaration, not necessarily the way that Fredrik suggested, but a way to pre-declare constants e.g.: const FOO = 27 And then require case expressions to be either literals or constants. The constants need not be computable at compile time, just runtime. If a constant is defined using a foldable expression (e.g. FOO = 27 + 43), then the compiler can always optimize it down to a code level constant. Otherwise, it can just put constants into cells that the functions use as part of their closure. (For that matter, the switch statement jump tables, if any, can be put in a cell too.) >I don't like "first use" because it seems to invite tricks. Okay, then I think we need a way to declare a global as being constant. It seems like all the big problems with switch/case basically amount to us trying to wiggle around the need to explicitly declare constants. ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] TRUNK is UNFROZEN, but in FEATURE FREEZE
Anthony Baxter <[EMAIL PROTECTED]> wrote: > 2.5b1 is out, so I'm declaring the SVN trunk unfrozen. Note, though, > that as we're now post-beta, we're in FEATURE FREEZE. Hey Raymond, any word on those binascii additions, or should I clean up that struct patch and add in some tests? - Josiah ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Code coverage reporting.
On Mon, Jun 19, 2006 at 02:21:04PM +1000, Nick Coghlan wrote: -> Brett Cannon wrote: -> >But it does seem accurate; random checking of some modules that got high -> >but not perfect covereage all seem to be instances where dependency -> >injection would be required to get the tests to work since they were -> >based on platform-specific things. -> -> There's something odd going on with __future__.py, though. The module level -> code all shows up as not executed, but the bodies of the two _Feature -> methods both show up as being run. -> -> I'm curious as to how a function body can be executed without executing the -> function definition first :) Coverage recording probably wasn't on at the time the module was imported; I only turn on recording in the 'runtest' function, and not before. I should probably start it earlier ;) -> As far as making the comments/docstrings less obvious goes, grey is usually -> a good option for that. I'll try it out and see... thanks, --titus ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
Brett Cannon's and Neal Norwitz's replies appreciated and noted, but responses sent by mail. Nick Coghlan <[EMAIL PROTECTED]> wrote: > > Python 2.4's decimal module is, in essence, a floating point emulator based > on > the General Decimal Arithmetic specification. Grrk. Format and all? Because, in software, encoding, decoding and dealing with the special cases accounts for the vast majority of the time. Using a format and specification designed for implementation in software is a LOT faster (often 5-20 times). > If you want floating point mathematics that doesn't have insane platform > dependent behaviour, the decimal module is the recommended approach. By the > time Python 2.6 rolls around, we will hopefully have an optimized version > implemented in C (that's being worked on already). Yes. There is no point in building a wheel if someone else is doing it. Please pass my name on to the people doing the optimisation, as I have a lot of experience in this area and may be able to help. But it is a fairly straightforward (if tricky) task. > That said, I'm not clear on exactly what changes you'd like to make to the > binary floating point type, so I don't know if I think they're a good idea or > not :) Now, here it is worth posting a reponse :-) The current behaviour follows C99 (sic) with some extra checking (e.g. division by zero raises an exception). However, this means that a LOT of errors will give nonsense answers without comment, and there are a lot of ways to 'lose' NaN values quietly - e.g. int(NaN). That is NOT good software engineering. So: Mode A: follow IEEE 754R slavishly, if and when it ever gets into print. There is no point in following C99, as it is too ill-defined, even if it were felt desirable. This should not be the default, because of the flaws I mention above (see Kahan on Java). Mode B: all numerically ambiguous or invalid operations should raise an exception - including pow(0,0), int(NaN) etc. etc. There is a moot point over whether overflow is such a case in an arithmetic that has infinities, but let's skip over that one for now. Mode C: all numerically ambiguous or invalid operations should return a NaN (or infinity, if appropriate). Anything that would lose the error indication would raise an exception. The selection between modes B and C could be done by a method on the class - with mode B being selected if any argument had it set, and mode C otherwise. Now, both modes B and C are traditional approaches to numerical safety, and have the property that error indications can't be lost "by accident", though they make no guarantees that the answers make sense. I am agnostic about which is better, though mode B is a LOT better from the debugging point of view, as you discover an error closer to where it was made. Heaven help us, there could be a mode D, which would be mode C but with trace buffers. They are another sadly neglected software engineering technique, but let's not add every bell and whistle on the shelf :-) "tjreedy" <[EMAIL PROTECTED]> wrote: > > > experience from times of yore is that emulated floating-point would > > be fast enough that few, if any, Python users would notice. > > Perhaps you should enquire on the Python numerical and scientific computing > lists to see how many feel differently. I don't see how someone crunching > numbers hours per day could not notice a slowdown. Oh, certainly, almost EVERYONE will "feel" differently! But that is not the point. Those few of us remaining (and there are damn few) who know how a fast emulated floating-point performs know that the common belief that it is very slow is wrong. I have both used and implemented it :-) The point is, as I mention above, you MUST use a software-friendly format AND specification if you want performance. IEEE 754 and IBM's decimal pantechnichon are both extremely software-hostile. Regards, Nick Maclaren, University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England. Email: [EMAIL PROTECTED] Tel.: +44 1223 334761Fax: +44 1223 334679 ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Code coverage reporting.
On Mon, Jun 19, 2006 at 08:37:30AM -0400, Benji York wrote:
-> Brett Cannon wrote:
-> >But it does seem accurate; random checking of some modules that got high
-> >but not perfect covereage all seem to be instances where dependency
-> >injection would be required to get the tests to work since they were
-> >based on platform-specific things.
->
-> >I don't know if we need it hooked into the buildbots (unless it is dirt
-> >cheap to generate the report).
->
-> It would be interesting to combine the coverage over several platforms
-> and report that.
Yes, I noticed that the platform specific stuff doesn't get covered, of
course. It's very easy to do, *if* there's any way to get the coverage
database from a central location (or send it back to a central location).
It might be interesting to run coverage analysis -- either figleaf or
Ned Batchelder's module[0] -- once a week on select buildbot machines
(one linux, one windows, one mac, or some such) and make the coverage
databases available via something like a downloadable static file. Then
anyone could download those files and do Interesting Things with them.
--titus
[0] I'm sorry, I don't know how Walter Dorwald generates his coverage;
if it's OSS, then it'd be better to use because it shows C code coverage
as well.
p.s. Here's the diff for regr_test:
Index: Lib/test/regrtest.py
===
--- Lib/test/regrtest.py(revision 46972)
+++ Lib/test/regrtest.py(working copy)
@@ -1,4 +1,5 @@
#! /usr/bin/env python
+import figleaf
"""Regression test.
@@ -333,7 +334,11 @@
tracer.runctx('runtest(test, generate, verbose, quiet, testdir)',
globals=globals(), locals=vars())
else:
+figleaf.start(False)
ok = runtest(test, generate, verbose, quiet, testdir, huntrleaks)
+figleaf.stop()
+figleaf.write_coverage('.figleaf')
+
if ok > 0:
good.append(test)
elif ok == 0:
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Re: [Python-Dev] Numerical robustness, IEEE etc.
Michael Hudson <[EMAIL PROTECTED]> wrote: > > > As I have posted to comp.lang.python, I am not happy with Python's > > numerical robustness - because it basically propagates the 'features' > > of IEEE 754 and (worse) C99. > > That's not really now I would describe the situation today. It is certainly the case in 2.4.2, however you would describe it. > > 2) Because some people are dearly attached to the current behaviour, > > warts and all, and there is a genuine quandary of whether the 'right' > > behaviour is trap-and-diagnose, propagate-NaN or whatever-IEEE-754R- > > finally-specifies (let's ignore C99 and Java as beyond redemption), > > Why? Maybe it's clear to you, but it's not totally clear to me, and > it any case the discussion would be better informed for not being too > dismissive. Why which? There are several things that you might be puzzled over. And where can I start? Part of the problem is that I have spent a LOT of time in these areas in the past decades, and have been involved with many of the relevant standards, and I don't know what to assume. > > there might well need to be options. These can obviously be done by > > a command-line option, an environment variable or a float method. > > There are reasons to disfavour the last, but all are possible. Which > > is the most Pythonesque approach? > > I have heard Tim say that there are people who would dearly like to be > able to choose. Environment variables and command line switches are > not Pythonic. All right, but what is? Firstly, for something that needs to be program-global? Secondly, for things that don't need to be brings up my point of adding methods to a built-in class. > I'm interested in making Python's floating point story better, and > have worked on a few things for Python 2.5 -- such as > pickling/marshalling of special values -- but I'm not really a > numerical programmer and don't like to guess what they need. Ah. I must get a snapshot, then. That was one of the lesser things on my list. I have spent a lot of the past few decades in the numerical programming arena, from many aspects. Regards, Nick Maclaren, University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England. Email: [EMAIL PROTECTED] Tel.: +44 1223 334761Fax: +44 1223 334679 ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Code coverage reporting.
On Sun, Jun 18, 2006 at 08:12:39PM -0700, Brett Cannon wrote: -> On 6/15/06, Titus Brown <[EMAIL PROTECTED]> wrote: -> > -> >Folks, -> > -> >I've just run a code coverage report for the python2.4 branch: -> > -> >http://vallista.idyll.org/~t/temp/python2.4-svn/ -> > -> >This report uses my figleaf code, -> > -> >http://darcs.idyll.org/~t/projects/figleaf-latest.tar.gz -> -> -> Very nice, Titus! -> -> I'm interested in feedback on a few things -- -> > -> >* what more would you want to see in this report? -> > -> >* is there anything obviously wrong about the report? -> > -> >In other words... comments solicited ;). -> -> Making the comments in the code stand out less (i.e., not black) might be -> handy since my eye still gets drawn to the comments a lot. I think I'd have to use the tokenizer to do this, no? The comments aren't kept in the AST, and I don't want to write a half-arsed regexp because I'm sure I'll stumble on comments in strings etc ;) -> It would also be nice to be able to sort on different things, such as -> filename. Easy enough; just the index needs to be generated in multiple ways. -> But it does seem accurate; random checking of some modules that got high but -> not perfect covereage all seem to be instances where dependency injection -> would be required to get the tests to work since they were based on -> platform-specific things. Great! -> By the by, I'm also planning to integrate this into buildbot on some -> >projects. I'll post the scripts when I get there, and I'd be happy -> >to help Python itself set it up, of course. -> -> -> I don't know if we need it hooked into the buildbots (unless it is dirt -> cheap to generate the report). But hooking it up to the script in -> Misc/build.sh that Neal has running to report reference leaks and -> fundamental test failures would be wonderful. Hmm, ok, I'll take a look. The general cost is a ~2x slowdown for running with trace enabled, and the HTML generation itself takes less than 5 minutes (all of that in AST parsing/traversing to figure out what lines *should* be looked at). cheers, --titus ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Numerical robustness, IEEE etc.
Michael Hudson <[EMAIL PROTECTED]> wrote: > > This mail never appeared on python-dev as far as I can tell, so I'm > not snipping anything. And it still hasn't :-( I am on the list of recipients without posting rights, and the moderator appears to be on holiday. > >>> As I have posted to comp.lang.python, I am not happy with Python's > >>> numerical robustness - because it basically propagates the > >>> 'features' > >>> of IEEE 754 and (worse) C99. > >> > >> That's not really now I would describe the situation today. > > > > It is certainly the case in 2.4.2, however you would describe it. > > I guess you could say it reflects the features of C89. It certainly > doesn't do anything C99 specific. Oh, yes, it does! If you look at floatobject.c, you will find it solid with constructions that make limited sense in C99 but next to no sense in C89. > But I wouldn't characterize anything Python does in the floating > point area as "designed", particularly. Portability makes that hard. Not really. We managed even back in the 1970s, when there was a LOT more variation. Writing code that would work, unchanged, on an IBM 360, an ICL 1900 and a CDC 6600 was, er, interesting > Why are C99 and Java beyond redemption? I know some of the mistakes > Java makes here, but still, you could at least hint at which you are > thinking of. Where do I start? Look at Kahan's "Why Java's Floating-Point Hurts Everyone, Everywhere" and then at the UK's reasons for voting "NO" to C99. There wasn't even an agreement on the INTENT of most of the new features in SC22WG14, and God alone knows what the C99 standard means (if anything). There is informative and optional text that overrides normative; there is wording that contradicts itself, or is otherwise meaningless; and so on. Plus the fact that the C99 standard is simultaneously unusable and unimplementable on many architectures. And the fact that most of it is numerically insane. I could go on > Well, if you can't explain what your intentions are to *me*, as a > mathematics-degree holding core Python developer that has done at > least some work in this area, I posit that you aren't going to get > very far. My intentions are to provide some numerically robust semantics, preferably of the form where straightforward numeric code (i.e. code that doesn't play any bit-twiddling tricks) will never invoke mathematically undefined behaviour without it being flagged. See Kahan on that. > I'm not intimately familiar with the standards like 754 but I have > some idea what they contain, and I've read appendix F of C99, if that > helps you target your explanations. Not a lot. Annex F in itself is only numerically insane. You need to know the rest of the standard, including that which is documented only in SC22WG14 messages, to realise the full horror. > Why does it need to be program global? In my not-really-thought-out > plans for straightening out CPython's floating point story I had > envisioned code to be written something like this: No, you are thinking at too low a level. The problem with such things is that they related to the interfaces between types, and it is those aspects where object-orientation falls down so badly. For example, consider conversion between float and long - which class should control the semantics? > This could be implemented by having a field in the threadstate of FPU > flags to check after each fp operation (or each set of fp operations, > possibly). I don't think I have the guts to try to implement > anything sensible using HW traps (which are thread-local as well, > aren't they?). Gods, NO!!! Sorry, but I have implemented such things (but that was on a far architecture, and besides the system is dead). Modern CPU architectures don't even DEFINE whether interrupt handling is local to the core or chip, and document that only in the release notes, but what is clear is that some BLACK incantations are needed in either case. Think of taking a machine check interrupt on a multi- core, highly-pipelined architecture and blench. And, if that is an Itanic, gibber hysterically before taking early retirement on the grounds of impending insanity. Oh, that's the calm, moderate description. The reality is worse. > > Secondly, for things that don't need to be brings > > up my point of adding methods to a built-in class. > > This isn't very hard, really, in fact float has class methods in 2.5... Thanks. I will look, but remember this is being done at the C level. > >> I'm interested in making Python's floating point story better, and > >> have worked on a few things for Python 2.5 -- such as > >> pickling/marshalling of special values -- but I'm not really a > >> numerical programmer and don't like to guess what they need. > > > > Ah. I must get a snapshot, then. That was one of the lesser things > > on my list. > > It was fairly straightforward, and still caused portability problems... Now
Re: [Python-Dev] Code coverage reporting.
Titus Brown wrote: > On Mon, Jun 19, 2006 at 08:37:30AM -0400, Benji York wrote: > -> Brett Cannon wrote: > -> >But it does seem accurate; random checking of some modules that got high > -> >but not perfect covereage all seem to be instances where dependency > -> >injection would be required to get the tests to work since they were > -> >based on platform-specific things. > -> > -> >I don't know if we need it hooked into the buildbots (unless it is dirt > -> >cheap to generate the report). > -> > -> It would be interesting to combine the coverage over several platforms > -> and report that. > > Yes, I noticed that the platform specific stuff doesn't get covered, of > course. It's very easy to do, *if* there's any way to get the coverage > database from a central location (or send it back to a central location). > > It might be interesting to run coverage analysis -- either figleaf or > Ned Batchelder's module[0] -- once a week on select buildbot machines > (one linux, one windows, one mac, or some such) and make the coverage > databases available via something like a downloadable static file. Then > anyone could download those files and do Interesting Things with them. > > --titus > > [0] I'm sorry, I don't know how Walter Dorwald generates his coverage; > if it's OSS, then it'd be better to use because it shows C code coverage > as well. The script at http://styx.livinglogic.de/~walter/python/coverage/PythonCodeCoverage.py definitely is open source, so feel free to use in any way you want. The web application front end though isn't open source. The SQL script to recreate the database can be found here: http://styx.livinglogic.de/~walter/python/coverage/coverage.sql Servus, Walter ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] PyRange_New() alternative?
http://docs.python.org/dev/whatsnew/ports.html says: The PyRange_New() function was removed. It was never documented, never used in the core code, and had dangerously lax error checking. I use this function (don't remember how I found it; this was years ago), therefore my code doesn't compile with 2.5b1 (it did OK before with 2.5a2). Is there an alternative spelling for PyRange_New()? Thank you in advance! Ralf __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] doc for new restricted execution design for Python
I have been working on a design doc for restricted execution of Python as part of my dissertation for getting Python into Firefox to replace JavaScript on the web. Since this is dealing with security and messing that up can be costly, I am sending it to the list for any possible feedback. I have already run the ideas past Neal, Guido, Jeremy, and Alex and everyone seemed to think the design was sound (thanks to them and Will for attending my meeting on it and giving me feedback that helped to shape this doc), so hopefully there are no major issues with the design itself. There are a couple of places (denoted with XXX) where there is an open issue still. Feedback on those would be great. Anyway, here it is. I am going to be offline most of tomorrow so I probably won't get back to comments until Friday. And just in case people are wondering, I plan on doing the implementation in the open on a branch within Python's repository so if this design works out it will end up in the core (as for when that would land, I don't know, but hopefully for 2.6). - Restricted Execution for Python ### About This Document = This document is meant to lay out the general design for re-introducing a restriced execution model for Python. This document should provide one with enough information to understand the goals for restricted execution, what considerations were made for the design, and the actual design itself. Design decisions should be clear and explain not only why they were chosen but possible drawbacks from taking that approach. Goal = A good restricted execution model provides enough protection to prevent malicious harm to come to the system, and no more. Barriers should be minimized so as to allow most code that does not do anything that would be regarded as harmful to run unmodified. An important point to take into consideration when reading this document is to realize it is part of my (Brett Cannon's) Ph.D. dissertation. This means it is heavily geared toward the restricted execution when the interpreter is working with Python code embedded in a web page. While great strides have been taken to keep the design general enough so as to allow all previous uses of the 'rexec' module [#rexec]_ to be able to use the new design, it is not the focused goal. This means if a design decision must be made for the embedded use case compared to sandboxing Python code in a Python application, the former will win out. Throughout this document, the term "resource" is to represent anything that deserves possible protection. This includes things that have a physical representation (e.g., memory) to things that are more abstract and specific to the interpreter (e.g., sys.path). When referring to the state of an interpreter, it is either "trusted" or "untrusted". A trusted interpreter has no restrictions imposed upon any resource. An untrusted interpreter has at least one, possibly more, resource with a restriction placed upon it. .. contents:: Use Cases / All use cases are based on how many untrusted or trusted interpreters are running in a single process. When the Interpreter Is Embedded Single Untrusted Interpreter This use case is when an application embeds the interpreter and never has more than one interpreter running. The main security issue to watch out for is not having default abilities be provided to the interpreter by accident. There must also be protection from leaking resources that the interpreter needs for general use underneath the covers into the untrusted interpreter. Multiple Untrusted Interpreters --- When multiple interpreters, all untrusted at varying levels, need to be running within a single application. This is the key use case that this proposed design is targetted for. On top of the security issues from a single untrusted interpreter, there is one additional worry. Resources cannot end up being leaked into other interpreters where they are given escalated rights. Stand-Alone Python == When someone has written a Python program that wants to execute Python code in an untrusted interpreter(s). This is the use case that 'rexec' attempted to fulfill. The added security issues for this use case (on top of the ones for the other use cases) is preventing something from the trusted interpreter leaking into an untrusted interpreter and having elevated permissions. With the multiple untrusted interpreters one did not have to worry about preventing actions from occurring that are disallowed for all untrusted interpreters. With this use case you do have to worry about the binary distinction between trusted and untrusted interpreters running in the same pr
[Python-Dev] ImportWarning flood
http://docs.python.org/dev/whatsnew/other-lang.html says: > One error that Python programmers sometimes make is forgetting to > include an __init__.py module in a package directory. Debugging this > mistake can be confusing, and usually requires running Python with the > -v switch to log all the paths searched. In Python 2.5, a new > ImportWarning warning is raised when an import would have picked up a > directory as a package but no __init__.py was found. I am getting tons of "ImportWarning: Not importing directory". See below for examples. It is impractical for me to reorganize our directory structure. I'd be busy for a week or more and people would probably scream at me because all the paths have changed. Are there other options to get rid of the warnings? Thanks! Ralf /net/rosie/scratch1/rwgk/dist/libtbx/libtbx/command_line/scons.py:1: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/libtbx': missing __init__.py from libtbx.utils import Sorry /net/rosie/scratch1/rwgk/py25b1/build/python/lib/python2.5/random.py:43: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/cctbx/math': missing __init__.py from math import log as _log, exp as _exp, pi as _pi, e as _e, ceil as _ceil /net/rosie/scratch1/rwgk/py25b1/build/python/lib/python2.5/random.py:43: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/scitbx/math': missing __init__.py from math import log as _log, exp as _exp, pi as _pi, e as _e, ceil as _ceil scons: Reading SConscript files ... /net/rosie/scratch1/rwgk/dist/scons/src/engine/SCons/Tool/__init__.py:112: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/scons/src/engine/SCons/Tool/CVS': missing __init__.py file, path, desc = imp.find_module(self.name, smpath) /net/rosie/scratch1/rwgk/dist/phenix/phenix/__init__.py:1: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/libtbx': missing __init__.py try: import libtbx.forward_compatibility /net/rosie/scratch1/rwgk/dist/phenix/phenix/refinement/__init__.py:1: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/iotbx': missing __init__.py import iotbx.phil /net/rosie/scratch1/rwgk/dist/iotbx/iotbx/phil.py:1: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/cctbx': missing __init__.py from cctbx import sgtbx /net/rosie/scratch1/rwgk/dist/cctbx/cctbx/array_family/flex.py:1: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/scitbx': missing __init__.py import scitbx.array_family.flex /net/rosie/scratch1/rwgk/dist/scitbx/scitbx/array_family/flex.py:2: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/boost': missing __init__.py import boost.optional /net/rosie/scratch1/rwgk/dist/libtbx/libtbx/utils.py:226: ImportWarning: Not importing directory '/net/rosie/scratch1/rwgk/dist/mmtbx': missing __init__.py try: module = __import__(module_path) etc. etc. __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Switch statement
Phillip J. Eby wrote: > At 09:55 AM 6/21/2006 -0700, Guido van Rossum wrote: > >>BTW a switch in a class should be treated the same as a global switch. >>But what about a switch in a class in a function? > > > Okay, now my head hurts. :) > > A switch in a class doesn't need to be treated the same as a global switch, > because locals()!=globals() in that case. > > I think the top-level is the only thing that really needs a special case > vs. the general "error if you use a local variable in the expression" rule. > > Actually, it might be simpler just to always reject local variables -- even > at the top-level -- and be done with it. I don't get what the problem is here. A switch constant should have exactly the bahavior of a default value of a function parameter. We don't seem to have too many problems defining functions at the module level, do we? -- Talin ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] Allow assignments in 'global' statements?
I'm sure I am not the first person to say this, but how about: global x = 12 (In other words, declare a global and assign a value to it - or another way of saying it is that the 'global' keyword acts as an assignment modifier.) -- Talin ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] ImportWarning flood
On 6/21/06, Ralf W. Grosse-Kunstleve <[EMAIL PROTECTED]> wrote: > I am getting tons of "ImportWarning: Not importing directory". See below for > examples. It is impractical for me to reorganize our directory structure. I'd > be busy for a week or more and people would probably scream at me because all > the paths have changed. Are there other options to get rid of the warnings? Check out the -W command line option and the warnings module. These document how to suppress warnings. -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] ImportWarning flood
--- Guido van Rossum <[EMAIL PROTECTED]> wrote: > On 6/21/06, Ralf W. Grosse-Kunstleve <[EMAIL PROTECTED]> wrote: > > I am getting tons of "ImportWarning: Not importing directory". See below > for > > examples. It is impractical for me to reorganize our directory structure. > I'd > > be busy for a week or more and people would probably scream at me because > all > > the paths have changed. Are there other options to get rid of the warnings? > > Check out the -W command line option and the warnings module. These > document how to suppress warnings. Thanks! This does the trick: python -W'ignore:Not importing directory' But this doesn't: python -W'ignore:Not importing directory:ImportWarning' I tried a bunch of variations without success. A few examples here would be very valuable: http://docs.python.org/lib/warning-filter.html Also, the magic incantation to silence the warnings would be very helpful here: http://docs.python.org/dev/whatsnew/other-lang.html Is there a way to set the warning options via an environment variable? Otherwise I am forced to use a wrapper or aliases. __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] Weekly Python Patch/Bug Summary
Patch / Bug Summary
___
Patches : 378 open ( +3) / 3298 closed (+34) / 3676 total (+37)
Bugs: 886 open (-24) / 5926 closed (+75) / 6812 total (+51)
RFE : 224 open ( +7) / 227 closed ( +7) / 451 total (+14)
New / Reopened Patches
__
Improve super() objects support for implicit method calls (2006-05-31)
http://python.org/sf/1498363 opened by Collin Winter
Improve itertools.starmap (2006-05-31)
http://python.org/sf/1498370 opened by Collin Winter
Change *args from a tuple to list (2006-05-31)
http://python.org/sf/1498441 opened by Collin Winter
Correctly unpickle exceptions (2006-06-01)
CLOSED http://python.org/sf/1498571 opened by iga Seilnacht
Fault in XMLRPC not always returned to client (2006-05-31)
CLOSED http://python.org/sf/1498627 opened by Daniel Savard
Generate from Unicode database instead of manualy coding. (2006-06-01)
http://python.org/sf/1498930 opened by Anders Chrigström
Optimise "in" operations on tuples of consts (2006-06-01)
CLOSED http://python.org/sf/1499095 opened by Collin Winter
Fix for memory leak in WindowsError_str (2006-06-02)
CLOSED http://python.org/sf/1499797 opened by iga Seilnacht
Alternate RFC 3896 compliant URI parsing module (2006-06-05)
http://python.org/sf/1500504 opened by Nick Coghlan
Remove dependencies on the sets module (2006-06-04)
http://python.org/sf/1500609 opened by Collin Winter
(py3k) Remove the sets module (2006-06-04)
http://python.org/sf/1500611 opened by Collin Winter
Remove the repr()-backticks (2006-06-04)
http://python.org/sf/1500623 opened by Collin Winter
wm_attributes doesn't take keyword arguments (2006-06-04)
http://python.org/sf/1500773 opened by Greg Couch
AF_NETLINK support for socket module (2006-06-05)
CLOSED http://python.org/sf/1500815 opened by lplatypus
Cyclic garbage collection support for slices (2006-06-05)
CLOSED http://python.org/sf/1501180 opened by iga Seilnacht
Fix Bug #1339007 - shelve.open('non-existant-file', 'r') (2006-06-06)
CLOSED http://python.org/sf/1501534 opened by Jeung Mun Sic
syntax errors on continuation lines (2006-06-06)
http://python.org/sf/1501979 opened by Roger Miller
Remove randomness from test_exceptions (2006-06-07)
CLOSED http://python.org/sf/1501987 opened by iga Seilnacht
Conditional compilation of zlib.(de)compressobj.copy (2006-06-08)
CLOSED http://python.org/sf/1503046 opened by Chris AtLee
Allow Empty Subscript List Without Parentheses (2006-06-09)
CLOSED http://python.org/sf/1503556 opened by Noam Raphael
Tiny patch to stop make spam (2006-06-09)
http://python.org/sf/1503717 opened by Chris AtLee
Rough documentation for xml.etree.ElementTree (2006-06-10)
http://python.org/sf/1504046 opened by Fredrik Lundh
Patch for 1496501 tarfile opener order (2006-06-10)
http://python.org/sf/1504073 opened by Jack Diederich
Switch syntax (partial PEP 275) (2006-06-11)
http://python.org/sf/1504199 opened by Thomas Lee
winerror module (2006-06-13)
http://python.org/sf/1505257 opened by M.-A. Lemburg
curses.resizeterm() (2006-06-15)
CLOSED http://python.org/sf/1506645 opened by Walter Dörwald
Patch for 1506758 - popen2/subprocess MAXFD MemoryErrors (2006-06-15)
http://python.org/sf/1506760 opened by Peter Vetere
Use a set to keep interned strings (2006-06-15)
http://python.org/sf/1507011 opened by Alexander Belopolsky
tarfile extraction does not honor umask (2006-06-16)
http://python.org/sf/1507247 opened by Faik Uygur
improve object.c and abstract.c exception messages (2006-06-17)
CLOSED http://python.org/sf/1507676 opened by Georg Brandl
transparent gzip compression in liburl2 (2006-06-19)
http://python.org/sf/1508475 opened by Jakob Truelsen
uuid documentation (2006-06-20)
http://python.org/sf/1508766 opened by George Yoshida
Make Lib/test/regrtest.py NetBSD 3 aware. (2006-06-20)
CLOSED http://python.org/sf/1509001 opened by Matt Fleming
MS Toolkit Compiler no longer available (2006-06-20)
http://python.org/sf/1509163 opened by Paul Moore
skip tests in test_socket__ssl when connection refused (2006-06-20)
CLOSED http://python.org/sf/1509404 reopened by bcannon
skip tests in test_socket__ssl when connection refused (2006-06-20)
CLOSED http://python.org/sf/1509404 opened by Brett Cannon
Small fix for sqlite3 test suite (2006-06-20)
CLOSED http://python.org/sf/1509584 opened by Gerhard Häring
tarfile stops iteration with some longfiles (2006-06-21)
CLOSED http://python.org/sf/1509889 opened by Faik Uygur
Patches Closed
__
Possible fix to #1334662 (int() wrong answers) (2006-03-31)
http://python.org/sf/1462361 closed by gbrandl
Correctly unpickle exceptions (2006-05-31)
http://python.org/sf/1498571 closed by gbrandl
Fault in XML
Re: [Python-Dev] ImportWarning flood
Ralf W. Grosse-Kunstleve wrote: > Is there a way to set the warning options via an environment variable? This is off-topic for python-dev, but: why don't switch off the warnings in the code? Regards, Martin ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] PyRange_New() alternative?
Ralf W. Grosse-Kunstleve wrote: > http://docs.python.org/dev/whatsnew/ports.html says: > > The PyRange_New() function was removed. It was never documented, never used > in the core code, and had dangerously lax error checking. > > I use this function (don't remember how I found it; this was years ago), > therefore my code doesn't compile with 2.5b1 (it did OK before with 2.5a2). Is > there an alternative spelling for PyRange_New()? You can call PyRange_Type with the appropriate parameters. Georg ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] Things to remember when adding *packages* to stdlib
I believe this change is all that's necessary on the Unix side to install wsgiref. Can someone please update the Windows build files to ensure wsgiref is installed in b2? Don't forget to update the NEWS entry too. Also, all committers and reviewers, try to remember that when a package (meaning directory) is added to the stdlib, we need to update Makefile.pre.in and the Windows build files. (I forgot this time too.) Is there some documentation that should be updated as a reminder? Maybe someone could come up with a heuristic to add to Misc/build.sh which we could test in there. n -- On 6/21/06, neal.norwitz <[EMAIL PROTECTED]> wrote: > Author: neal.norwitz > Date: Thu Jun 22 08:30:50 2006 > New Revision: 47064 > > Modified: >python/trunk/Makefile.pre.in >python/trunk/Misc/NEWS > Log: > Copy the wsgiref package during make install. > > > > Modified: python/trunk/Makefile.pre.in > == > --- python/trunk/Makefile.pre.in(original) > +++ python/trunk/Makefile.pre.inThu Jun 22 08:30:50 2006 > @@ -708,7 +708,7 @@ > encodings compiler hotshot \ > email email/mime email/test email/test/data \ > sqlite3 sqlite3/test \ > - logging bsddb bsddb/test csv \ > + logging bsddb bsddb/test csv wsgiref \ > ctypes ctypes/test ctypes/macholib idlelib idlelib/Icons \ > distutils distutils/command distutils/tests $(XMLLIBSUBDIRS) \ > setuptools setuptools/command setuptools/tests > setuptools.egg-info \ > > Modified: python/trunk/Misc/NEWS > == > --- python/trunk/Misc/NEWS (original) > +++ python/trunk/Misc/NEWS Thu Jun 22 08:30:50 2006 > @@ -19,6 +19,8 @@ > - The compiler module now correctly compiles the new try-except-finally >statement (bug #1509132). > > +- The wsgiref package is now installed properly on Unix. > + > > > What's New in Python 2.5 beta 1? > ___ > Python-checkins mailing list > [EMAIL PROTECTED] > http://mail.python.org/mailman/listinfo/python-checkins > ___ Python-Dev mailing list [email protected] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
