Mailman 3 September 2009 - Python-Dev

PyMem_Malloc() vs PyObject_Malloc()
by Kristján Valur Jónsson Sept. 4, 2009

Sept. 4, 2009

I noticed something (in 2.5) yesterday, which may be a feature, but is more likely a bug. In tokenizer.c, tok->encoding is allocated using PyMem_MALLOC(). However, this then gets handed to a node->r_str in parsetok.c, and then released in node.c using PyObject_Free(). Now, by coincidence, PyObject_Free() will default to free() for objects that it doesn't recognize, so this works. But is this documented behavior? The reason I ran into this was that I had redirect the PyMem_* API to a different allocator, but left the PyObject_* one alone. My feeling Is that these two APIs shouldn't be interchangeable. Especially since you can't hand a PyObject_Malloc'd object to PyMem_Free() so the inverse shouldn't be expected to work. Any thoughts? Kristján

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default of returning None hurts performance?
by Gregory P. Smith Sept. 4, 2009

Sept. 4, 2009

food for thought as noticed by a coworker who has been profiling some hot code to optimize a library... If a function does not have a return statement we return None. Ironically this makes the foo2 function below faster than the bar2 function at least as measured using bytecode size: Python 2.6.2 (r262:71600, Jul 24 2009, 17:29:21) [GCC 4.2.2] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import dis >>> def foo(x): ... y = x() ... return y ... >>> def foo2(x): ... return x() ... >>> def bar(x): ... y = x() ... >>> def bar2(x): ... x() ... >>> dis.dis(foo) 2 0 LOAD_FAST 0 (x) 3 CALL_FUNCTION 0 6 STORE_FAST 1 (y) 3 9 LOAD_FAST 1 (y) 12 RETURN_VALUE >>> dis.dis(foo2) 2 0 LOAD_FAST 0 (x) 3 CALL_FUNCTION 0 6 RETURN_VALUE >>> dis.dis(bar) 2 0 LOAD_FAST 0 (x) 3 CALL_FUNCTION 0 6 STORE_FAST 1 (y) 9 LOAD_CONST 0 (None) 12 RETURN_VALUE >>> dis.dis(bar2) 2 0 LOAD_FAST 0 (x) 3 CALL_FUNCTION 0 6 POP_TOP 7 LOAD_CONST 0 (None) 10 RETURN_VALUE

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OT : Cannot login to PyPI using MyOpenId
by Olemis Lang Sept. 4, 2009

Sept. 4, 2009

I realized that PyPI accepts MyOpenId and tried to login to the site. In the process I get this message : {{{ OpenID provider did not provide your email address }}} I mean, is it mandatory to provide the e-mail address in order to bind a user to an OpenId ? I'm curious : I'd like to know if there's a reason to do that. Thnx in advance ! PS: I know is a little bit OT. Hope you dont mind ... -- Regards, Olemis. Blog ES: http://simelo-es.blogspot.com/ Blog EN: http://simelo-en.blogspot.com/ Featured article:

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REMINDER: PyCon 2010: Call for Proposals
by Aahz Sept. 4, 2009

Sept. 4, 2009

Call for proposals -- PyCon 2010 -- <http://us.pycon.org/2010/> =============================================================== Due date: October 1st, 2009 Want to showcase your skills as a Python Hacker? Want to have hundreds of people see your talk on the subject of your choice? Have some hot button issue you think the community needs to address, or have some package, code or project you simply love talking about? Want to launch your master plan to take over the world with python? PyCon is your platform for getting the word out and teaching something new to hundreds of people, face to face. Previous PyCon conferences have had a broad range of presentations, from reports on academic and commercial projects, tutorials on a broad range of subjects and case studies. All conference speakers are volunteers and come from a myriad of backgrounds. Some are new speakers, some are old speakers. Everyone is welcome so bring your passion and your code! We're looking to you to help us top the previous years of success PyCon has had. PyCon 2010 is looking for proposals to fill the formal presentation tracks. The PyCon conference days will be February 19-22, 2010 in Atlanta, Georgia, preceded by the tutorial days (February 17-18), and followed by four days of development sprints (February 22-25). Online proposal submission is open now! Proposals will be accepted through October 1st, with acceptance notifications coming out on November 15th. For the detailed call for proposals, please see: <http://us.pycon.org/2010/conference/proposals/> For videos of talks from previous years - check out: <http://pycon.blip.tv> We look forward to seeing you in Atlanta! -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ "Look, it's your affair if you want to play with five people, but don't go calling it doubles." --John Cleese anticipates Usenet

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Py_CmpToRich removed, alternatives for comparison?
by Campbell Barton Sept. 2, 2009

Sept. 2, 2009

For blender we have a number of types defined in the C/API like meshes, lamps, metaballs, nurbs etc that dont make sense with some of richcmp's operations. A problem I have is that in python 3.1 the Py_CmpToRich function is removed. Should we copy Py_CmpToRich into our source tree? Otherwise we have fairly long cmp functions that have Py_CmpToRich inline. For C extension writers what is the suggested method for comparing types where Py_LT, Py_GT Py_GE etc are not useful? Since people sometimes ask why use py3.1, we're doing a rewrite that wont be ready for quite some time. -- - Campbell

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Decorator syntax
by Rob Cliffe Sept. 2, 2009

Sept. 2, 2009

Hi All, This is my first post to python-dev so I will briefly introduce myself: My name is Rob Cliffe and I am a commercial programmer living in London, UK. I have some 30 years of programming experience but have only been using Python for a couple of years. First I want to say what a fantastic language Python is. It is THE best language for development in my opinion, and a joy to use. My specific issue: I eventually got my head round decorator syntax and realised that what came after the '@' was (basically) a function that took a function as argument and returned a function as result. However it seems to me unPythonesque (i.e. an exception to Python's normal consistency) that the syntax of what follows the '@' should be restricted to either a single (function) identifier or a single (function) identifier with an argument list. The example I tried, which seems not an unreasonable sort of thing to do, was along the lines of: def deco1(func): <deco1-suite> def deco2(func): <deco2-suite> DecoList = [deco1, deco2] @DecoList[0] # NO - CAUSES SYNTAX ERROR def foo(): pass I am sure other guys have their own examples. I am of course not the first person to raise this issue, and I see that Guido has a "gut feeling" against allowing a general expression after the '@'. BUT - a general expression can be "smuggled in" very easily as a function argument: def Identity(x): return x @Identity(DecoList[0]) # THIS WORKS def foo(): pass So - the syntax restriction seems not only inconsistent, but pointless; it doesn't forbid anything, but merely means we have to do it in a slightly convoluted (unPythonesque) way. So please, Guido, will you reconsider? Best wishes Rob Cliffe

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Bugs discovered by researchers at Case Western Reserve University
by Boya Sun Sept. 2, 2009

Sept. 2, 2009

Dear Developers, I am a Ph.D student from Case Western Reserve University, specialized at software engineering. Our recent approach analyzes bugs that are being fixed in the issue database, and tries to discover any latent bug instances that are the same as the fixed bug but are left unfixed. We have found some spurious code in your project in this approach, and pointed out these code by comments (sometimes also with patches) to the fixed bugs in the issue DB from which it is discovered as follows: Issue 6817: http://bugs.python.org/issue6817 (A new issue, created following Amaury's comments) Issue 2620: http://bugs.python.org/issue2620 Issue 3139: http://bugs.python.org/issue3139 Issue 5705: http://bugs.python.org/issue5705 We hope that we have discovered some real bugs for you. Any comments or suggestions are GREATLY appreciated, since your opinions are very, very precious to us. Boya -- BOYA SUN Computer Science Division Electrical Engineering & Computer Science Department 513 Olin Building Case Western Reserve University 10900 Euclid Avenue Cleveland, OH 44106 boya.sun(a)case.edu

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Setting up a buildbot
by Paul Moore Sept. 2, 2009

Sept. 2, 2009

I've just had a look on python.org, but couldn't immediately see a pointer to instructions on what the process is to set up a buildbot. There's a not on setting things up for pybots, but nothing on the core buildbot setup. The reason I'm asking is that I'm thinking of seeing if I could set up a Windows buildbot of some sort, to offer extra coverage. It's early days, yet, but I wonder if someone could answer a few questions for me: - Is there any documentation on how to set up a buildbot? If so, can someone give me a pointer? - What configurations would be most useful? (I've got a 64-bit PC, so I can theoretically set up 32 or 64 bit VMs with VMWare, and with my shiny new MSDN subscription, I can set up whatever OS is most useful). - Is it possible to set up the pull/build/test side of the process separately, before linking it into the full buildbot farm? That would let me try things out on my own, and iron out any configuration glitches before dumping it on the world. Thanks for any pointers. It's early days yet, so it may be a while before I have anything properly set up, but I'd like to see what I can do. Paul.

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why different between staticmethod and classmethod on non-callable object?
by xiaobing jiang Sept. 2, 2009

Sept. 2, 2009

hi all: In the svn thunk tree, I find in file Object/funcobject.c, the two functions: sm_init and cm_init have a little different. the cm_init function will check the object is really callable, but the sm_init don't. the code like this: if (!PyCallable_Check(callable)) { PyErr_Format(PyExc_TypeError, "'%s' object is not callable", callable->ob_type->tp_name); return -1; } so when use staticmethod and classmethod on a class variable, there are two different behavior. class Test(object): name = "s7v7nislands" name = classmethod(Test.name) # will raise error. name = staticmethod(Test.name) # will not raise error. My idea is: here, the two functions (or maybe classes) should have the same behavior). so is this a bug or something I missing ? thanks! s7v7nislands

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Whether to call Py_Finalize when exiting from the child process of a fork from a spawned thread
by Reid Kleckner Sept. 1, 2009

Sept. 1, 2009

Hi all, I'm working on http://bugs.python.org/issue6642 for unladen swallow (because it happens to bite us in a weird way), and Jeff Yasskin told me to ask python-dev what the proper behavior should be at exit from the child process of a fork from a spawned thread. Right now, it seems that there is an assumption that when exiting the process, control will always return through Py_Main, which in turn calls Py_Finalize, to do things like GC and calling atexit handlers. Normally, if you fork a process from the main thread, this assumption will remain true, because main and Py_Main are still at the bottom of the stack in the child process. However, if you fork from a spawned thread, then the root of the stack will be the thread bootstrap routine for the platform's pythreads implementation. On one hand, you may not want to call the user's atexit handlers multiple times from different processes if they have externally visible effects. On the other hand, people seem to assume that Py_Finalize will be called at process exit to do various cleanups. On the third hand, maybe Python could just clear out all the atexit handlers in the child after a fork. So what should the correct behavior be? Thanks, Reid

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