Mailman 3 September 2002 - Python-Dev

ReST-ing Misc/NEWS
by Skip Montanaro 20 Sep '02

20 Sep '02

I just checked in a ReST-ified version of Misc/NEWS. While the total number of changes was fairly large, the number of different types of changes made were quite small. The overwhelming majority of changes involved properly highlighting section and subsection headers. I'll review the changes here so that people who modify this file in the future will be able to easily adapt to the new format. First, to process Misc/NEWS using ReST, you'll need the latest docutils snapshot: http://docutils.sf.net/docutils-snapshot.tgz David Goodger made a change to the allowable structure of internal references which simplified my job significantly. The changes required fell into the following categories: * The top-level "What's New" section headers changed to: What's New in Python 2.3 alpha 1? ================================= *XXX Release date: DD-MMM-2002 XXX* * Subsections are underlined with a single row of hyphens: Type/class unification and new-style classes -------------------------------------------- * Places where "balanced" single quotes were used were switched to use just apostrophes (`string' -> 'string'). * In a few places asterisks needed to be escaped which would otherwise have been interpreted as beginning blocks of italic or bold text, e.g.: - The type of tp_free has been changed from "void (*)(PyObject \*)" to "void (*)(void \*)". Note that only the asterisks preceded by whitespace needed to be escaped. * One instance of a word ending with an underscore needed to be quoted ("PyCmp_" became "``PyCmp_``"). * One table was converted to ReST form (search Misc/NEWS for "New codecs" for this example). * A few places where chunks of code or indented text were displayed needed to be properly introduced (preceding paragraph terminated by "::" and the chunk of code or text indented w.r.t. the paragraph). For example: - Note that PyLong_AsDouble can fail! This has always been true, but no callers checked for it. It's more likely to fail now, because overflow errors are properly detected now. The proper way to check: :: double x = PyLong_AsDouble(some_long_object); if (x == -1.0 && PyErr_Occurred()) { /* The conversion failed. */ } Not yet addressed is whether to automatically convert Misc/NEWS to other formats (such as HTML). I assume an automatic conversion to HTML is in the cards, with the output made available on the python.org website. Skip

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information needed
by Srinivas Rao Kollipara 20 Sep '02

20 Sep '02

Hi, I have a small python code, is there any tool which can convert the python code to oracle plsql code. Thanks kolli

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Re: mysterious hangs in socket code
by Mats Wichmann 19 Sep '02

19 Sep '02

>> One possibility is that the Linux getaddrinfo() is thread-safe, but >> only by way of a lock that only allows one request to be outstanding >> at a time. > >The next step should be to get the getaddrinfo() source code from >glibc and see what it does. It's open source, hey. :-) I can dig around a bit, but I have to figure out what I'm looking for. On the failure platform, are we sure Python is using the native getaddrinfo, not the Python-supplied one? I've had some fun (not) with the latter; for working on an LSB-conforming version of Python, I can't let it use the glibc version of getaddrinfo because it's not in the spec (will be in the next version); but the Python addrinfo.h header has some fields in different order than the Linux one, and it managed to call the Linux one anyway. The result of that was not subtle, however :-) so I don't think that's the problem that started this thread. I do know the Linux (or rather, glibc) getaddrinfo doesn't get rentrancy through magic, it calls gethostbyname_r and gethostbyaddr_r. (Note the Python emulation getaddrinfo just calls the straight gethostbyname and gethostbyaddr routines and so is likely not to be reentrant).

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CVS hosed?
by Thomas Heller 19 Sep '02

19 Sep '02

I cannot reach python's CVS repository. Should I look on my side for a problem, or is it the same for other developers? Thanks, Thomas

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How pass array from C to python function
by Praveen Patil 19 Sep '02

19 Sep '02

Hi , I have problem in passing array to python function. Please help me passing array to python function. Here is my 'C' program ----------------------- void RECEIVE_IL_STATE_S( int Instance , int vital_data[5]) { PyObject*arglist; PyObject* ret; PyObject* mylist; int count; mylist = PyList_New(5); for (count=0; count< 5; count++) { myint = PyInt_FromLong(vital_data[count]); PyList_Append(mylist,myint); } arglist = Py_BuildValue("O", mylist); ret = PyEval_CallObject(my_callback , arglist); Py_DECREF(arglist); Py_DECREF(ret); } Here is my Python program ------------------------- G_Logfile = None def TestFunction(a): G_Logfile = open('Pytestfile.txt', 'w') G_Logfile.write("%d \n"% a[0]) G_Logfile.write("%d \n"% a[1]) G_Logfile.close Cheers, Praveen. [ The information contained in this e-mail is confidential and is intended for the named recipient only. If you are not the named recipient, please notify us by telephone on +44 (0)1249 442 430 immediately, destroy the message and delete it from your computer. Silver Software has taken every reasonable precaution to ensure that any attachment to this e-mail has been checked for viruses. However, we cannot accept liability for any damage sustained as a result of any such software viruses and advise you to carry out your own virus check before opening any attachment. Furthermore, we do not accept responsibility for any change made to this message after it was sent by the sender.]

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ANNOUNCE -- Python-idle to Idlefork Merge Completed
by kbk＠shore.net 18 Sep '02

18 Sep '02

Python-idle has been merged into Idlefork as of 13 Sep 2002. I believe there are no Python-idle check-ins after that date, and since there will not be any future check-ins this should be the final merge from Python-idle. The Idlefork CVS is again open for business! Please submit bugs and patches to the Idlefork Tracker and any comments to the Idle-dev list. KBK

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Idle Development
by kbk＠shore.net 17 Sep '02

17 Sep '02

Guido posted a moratorium on futher Python Idle development, with the intention that work be shifted to Idlefork. I'd like to extend an invitation to any interested developers with Python CVS access to join the Idlefork project and continue in their idle ways. Send me an email and I'll set you up with Idlefork access. KBK

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Weeding out obsolete modules and Demos
by Jack Jansen 17 Sep '02

17 Sep '02

Folks, how about going over the various demos, and see which ones have really lost their usefulness? I happened to come across Demo/sgi/audio (works only on SGI 4D/35 machines, which went out of production about 12 years ago), sv and video (works on Indigo's with the Starter Video board, last seen about 8 years ago). And there's the svmodule.c (yup, same board). There are probably Indigo's still alive (4D35's? I doubt it, I can still remember the noise it made:-), but I wonder whether anyone in their right mind is still using the SV board. The forms/fl stuff still technically works on newer SGI's, but we might also wonder how useful they still are. And this is for SGI only, there's probably a lot more dead wood out there, -- - Jack Jansen <Jack.Jansen(a)oratrix.com> http://www.cwi.nl/~jack - - If I can't dance I don't want to be part of your revolution -- Emma Goldman -

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flextype.c -- extended type system
by Christian Tismer 17 Sep '02

17 Sep '02

Hi Guido, py-dev, preface: -------- a week ago or so, I sent a patch to Guido that removes the "etype" struct. This is a hidden structure that extends types when they are allocated on the heap. One restriction with this type was that types could not be extended by metatypes for some internal reason. I fixed this. Now meta-types can define extra slots for types. the point: ---------- I wasn't really after slots in types, but I wanted to have a type that can be extended as the user likes to. Using the re-worked etype (now named PyHeapType_Type), I created a new meta-type with some cool new features which give you C++ - like virtual methods and inheritance. The new dynamic type (PyFlexType_Type) allows to clone any existing type, and thereby to pass a virtual method table which will be bound into the type. It is a bit like slots and slot definitions, but the VMT definition is written like a PyMethodDef list (in fact, I have PyCMethodDef), and the created virtual function entries are spelled explicitly in the type structure. Structure of a VMT definition: typedef struct _pycmethoddef { char *name; /* name to lookup in __dict__ */ PyCFunction match; /* to be found if non-overridden */ void *fast; /* native C call */ void *wrap; /* wrapped call into Python */ int offset; /* slot offset in heap type */ } PyCMethodDef; At creation time of a new flextype, all VMT entries in the accumulated bases (accessed via the MRT) are scanned from oldest to newest, and the new type's methods are retrieved by the "name" entry. Then it is checked whether the method descriptor still points to the original PyCFunction entry (the "match" field). If it is still original, the native C call (field "fast") is inserted into the VMT, otherwise the wrapped Python callback (field "wrap") is inserted. As a result, it is now very cheap to use overridable small methods in your C implementations, since it nearly comes to no cost if the method isn't overridden. It is also possible to have private methods, in the sense that you can use inheritance between your flextypes without publishing every virtual method to Python at all. Here an example of my Stackless type system, where I made my channel interface overridable: (channelobject.h) """ #define CHANNEL_SEND_HEAD(func) \ int func (PyChannelObject *self, PyObject *arg) #define CHANNEL_SEND_EXCEPTION_HEAD(func) \ int func (PyChannelObject *self, PyObject *klass, PyObject *value) #define CHANNEL_RECEIVE_HEAD(func) \ PyObject * func (PyChannelObject *self) typedef struct _pychannel_heaptype { PyFlexTypeObject type; /* the fast callbacks */ CHANNEL_SEND_HEAD( (*send) ); CHANNEL_SEND_EXCEPTION_HEAD( (*send_exception) ); CHANNEL_RECEIVE_HEAD( (*receive) ); } PyChannel_HeapType; int init_channeltype(void); """ Here the VMT definition of channelobject.c: """ static PyCMethodDef channel_cmethods[] = { CMETHOD_PUBLIC_ENTRY(PyChannel_HeapType, channel, send), CMETHOD_PUBLIC_ENTRY(PyChannel_HeapType, channel, send_exception), CMETHOD_PUBLIC_ENTRY(PyChannel_HeapType, channel, receive), {NULL} /* sentinel */ }; """ where the CMETHOD_PUBLIC_ENTRY macro looks like this: /* * a public entry defines * - the function name "name" * - the PyCFunction class_name seen from Python, * - the fast function impl_class_name implements the method for C * - the wrapper function wrap_class_name that calls back into a Python override. */ #define CMETHOD_PUBLIC_ENTRY(type, prefix, name) \ {#name, (PyCFunction)prefix##_##name, &impl_##prefix##_##name, &wrap_##prefix##_##name, \ offsetof(type, name)} So basically three functions are involved in a virtual method: the PyCFunction, the C implementation and a wrapper. Normally, the PyCFunction and the implementation can be identical, but usually my C interface looks slightly different from the Python interface, for convenience. Here an excerpt from channel_send: """ int PyChannel_Send(PyChannelObject *self, PyObject *arg) { PyChannel_HeapType *t = (PyChannel_HeapType *) self->ob_type; return t->send(self, arg); } static CHANNEL_SEND_HEAD(impl_channel_send) { PyThreadState *ts = PyThreadState_GET(); PyTaskletObject *sender, *receiver; .... implementation skipped .... } static CHANNEL_SEND_HEAD(wrap_channel_send) { PyObject * ret = PyObject_CallMethod((PyObject *) self, "send", "(O)", arg); return slp_return_wrapper(ret); } static PyObject * channel_send(PyObject *myself, PyObject *arg) { if (impl_channel_send((PyChannelObject*)myself, arg)) return NULL; Py_INCREF(Py_None); return Py_None; } """ end of story. Summary: -------- Overridable methods have always been present in Python, via the built-in method slots. My extension methods give the same functionality to the user, at maximum possible speed (only templates can be faster). The benefit is that users can use much more flexibility in C modules than before, without fear of speed loss. I believe that virtual methods will be used more often, since it is cheap, flexible and compatible with Python. Please let me know if there is interest to use this techique in the Python core. I'm also not sure how to show the complete thing, since it is partially a patch to the existing type implementation (concerning the etype), partially a new C module flextype.c, and the rest is part of Stackless. Does it make sense (would somebody look at it) if I create a little demo application or something? cheers - chris -- Christian Tismer :^) <mailto:tismer@tismer.com> Mission Impossible 5oftware : Have a break! Take a ride on Python's Johannes-Niemeyer-Weg 9a : *Starship* http://starship.python.net/ 14109 Berlin : PGP key -> http://wwwkeys.pgp.net/ work +49 30 89 09 53 34 home +49 30 802 86 56 pager +49 173 24 18 776 PGP 0x57F3BF04 9064 F4E1 D754 C2FF 1619 305B C09C 5A3B 57F3 BF04 whom do you want to sponsor today? http://www.stackless.com/

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Moratorium on changes to IDLE
by Guido van Rossum 17 Sep '02

17 Sep '02

I'd like to put a stop to all changes to the version of IDLE in the Python source tree (Tools/idle/* -- let's call it Python-idle). The current crop of changes are being merged into Idlefork, the separate SF project where a new IDLE version is being cooked. I hope that Idlefork will be ready to be merged back into Python before we release Python 2.3, and that will be easiest if we can simply abandon the existing Python-idle code and copy the latest Idlefork in its place. Any changes made to the Python-idle code will be lost at that point. If you have a bug, fix or feature for IDLE, please suggest it on the idle-dev mailing list or on Idlefork's SF bug/patch managers! --Guido van Rossum (home page: http://www.python.org/~guido/)

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