🌐 Mailman 3 March 2009 - Python-list - python.org

An executable operational semantics for Python
by gideon April 6, 2009

April 6, 2009

Hi everybody, I've recently finished my Master's thesis on the semantics of Python. In my thesis I define the semantics of Python by rewriting an abstract machine. The sources that are used to produce my thesis can also be compiled into a working interpreter. Hence I call it an 'executable' semantics. Anyone interested should have a look at the short intro I put on my web page: http://gideon.smdng.nl/2009/01/an-executable-operational-semantics-for-pyth…

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CPython and C++ object GC
by csaba.balazs＠gmail.com April 5, 2009

April 5, 2009

Hello Everybody, I would like to use a C++ gui library with the following (simplified) interface in Python. #include <stdio.h> class Gui; class GuiObject { public: GuiObject(Gui *Gui) {printf("creating GuiObject(gui: %X)\n", Gui);} ~GuiObject() {printf("deleting GuiObject\n");} void Move(int x, int y) {printf("GuiObject move(%d, %d)\n", x, y);}; }; class Gui { public: Gui() {printf("creating Gui\n");} ~Gui() {printf("deleting Gui\n");} GuiObject* AddImage() { GuiObject* ob = new GuiObject(this); return ob; } void Print() {printf("Gui: %X\n", this);} }; int main() { Gui *gui = new Gui(); gui->Print(); GuiObject *obj = gui->AddImage(); obj->Move(50, 50); /*GuiObject *obj2 = new GuiObject(gui); // not allowed delete obj2;*/ delete obj; delete gui; return 0; } I created the Python Gui and GuiObject classes (PyTypeObject), and added it to main module (PyModule_AddObject). It works, but there is a problem at the Gui::AddImage(), with constructs a new GuiObject, which is available in Python layer but finally it is not collected and freed by GC: ... obj = _PyObject_New(&GuiObjectType); PyObject_Init(obj, &GuiObjectType); ... I cannot invoke the GuiObject object constructor directly from Python, because of the implementation of the C++ gui library (in this case it would be collected). I use the embedded CPython as an interpreter, so I cannot add additional external .py file for it. So the following Python code would be the target: gui = GUI(); background = gui.AddImage(); #background = GuiObject(gui); <-- Collected but not allowed background.ImageFile("bg.jpg"); background.Move(0, 0); ... How could I implement the AddImage function in order to be freed the constructed object at the end? Thanks in advance! All-the-best, Csaba

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Re-raising exceptions with a different type and message, preserving existing information
by Ben Finney April 5, 2009

April 5, 2009

Howdy all, I'm writing a module and want to have a unified exception hierarchy for the exceptions that it can raise. This allows users of the module to catch those particular exceptions and handle them distinctly, if needed. But many of the exceptions raised from the module are raised because of some other exception; e.g. failing at some task because of an OSError on a file. What I need is to “wrap” the exception caught such that it has a different type and message. But I don't want to lose the existing type, message, and stack trace; that's all useful information for someone trying to debug the problem. Python's PEP 3134 “Exception Chaining and Embedded Tracebacks” discusses a change accepted in Python 3.0 for “chaining” exception objects, to indicate that a new exception was raised during the handling of an existing exception. What I'm trying to do is related: I need it working in earlier Python versions, and I need it not for chaining, but only for polymorphism. What is the right way to do this? -- \ “… whoever claims any right that he is unwilling to accord to | `\ his fellow-men is dishonest and infamous.” —Robert G. | _o__) Ingersoll, _The Liberty of Man, Woman and Child_, 1877 | Ben Finney

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dict view to list
by Aaron Brady April 4, 2009

April 4, 2009

Hi. Is there a possibility of the dict_values, dict_items, and dict_keys objects growing a 'tolist' method? It's one of those little things that contributes to one's user experience. P.S. Yes, yes, I know, -1.

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how to optimize zipimport
by Coonay April 4, 2009

April 4, 2009

in my mudule ,i import another mudule from a zip , when i call my mudle method,the module in the zip will be import from the zip every time,that slow down the operation, i try to search the some workarodnd or solution but i don't get one, could you help me ?

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Re: Unix programmers and Idle
by Niklas Norrthon April 4, 2009

April 4, 2009

On 31 Mar, 01:16, Dale Amon <a...(a)vnl.com> wrote: > I wonder if someone could point me at documentation > on how to debug some of the standard Unix type things > in Idle. I cannot seem to figure out how to set my > argument line for the program I am debugging in an Idle > window. for example: > > vlmdeckcheck.py --strict --debug file.dat > > There must be a way to tell it what the command line args > are for the test run but I can't find it so far. As others have said it isn't. This is what I do: I make sure my scripts are on the form: # imports # global initialization (not depending on sys.argv) def main(): # initialization (might depend on sys.argv) # script logic # other functions if __name__ == '__main__': main() Then I have a trivial debug script named debug_whatever.py, which I use as my entry point during debugging: # debug_whatever.py: import sys sys.argv[1:] = ['arg1', 'arg2', 'arg3'] import whatever whatever.main() /Niklas Norrthon

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Unix programmers and Idle
by Dale Amon April 3, 2009

April 3, 2009

I wonder if someone could point me at documentation on how to debug some of the standard Unix type things in Idle. I cannot seem to figure out how to set my argument line for the program I am debugging in an Idle window. for example: vlmdeckcheck.py --strict --debug file.dat There must be a way to tell it what the command line args are for the test run but I can't find it so far.

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minor revision encoded in SONAME in libpython.so
by szager＠gmail.com April 3, 2009

April 3, 2009

I'm wondering why the SONAME in libpython.so has a minor revision encoded in it; for example (on Linux): $ readelf -d libpython2.6.so | grep SONAME 0x0000000e (SONAME) Library soname: [libpython2.6.so.1.0] Because of this, if I compile an app against this library (with '-L/ usr/lib -lpython2.6), the compiled app has a dependency in this precise minor revision of libpython2.6.so: $ readelf -d myApp | grep libpython 0x0000000000000001 (NEEDED) Shared library: [libpython2.6.so.1.0] So, for example, if I upgrade to libpython2.6.so.1.1, my app will not be able to run. I am currently having this problem while integrating a piece of third-party software that uses an embedded python interpreter. This is unusual for libraries of this kind. Typically, the SONAME will contain only the major revision, on the assumption that all the minor revisions conform to the same public API, and are nominally interchangeable. Am I to assume that minor version iterations have incompatible API's? Thanks in advance for any guidance.

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Re: c.l.py dead, news at 11 (was Re: Mangle function name with decorator?)
by Paul Rubin April 3, 2009

April 3, 2009

"Hendrik van Rooyen" <mail(a)microcorp.co.za> writes: > Its kind of sad to see unladen swallow, which is just > a promise, on the list, while Shedskin, which isn't, > is ignored. > > Does this say something about big corporations > vs the small man? I think the programs on the list were supposed to actually implement Python and extensions of Python, but not incompatible dialects. Otherwise Pyrex (for example) would also be on the list.

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Regression test
by Colin J. Williams April 3, 2009

April 3, 2009

I am running a regression test, mainly because I wish to explore subprocess, and get a number of errors before crashing. Is this to be expected? The run output is below. Colin W. C:\Documents and Settings\cjw\Desktop>C:\python26\python.exe Python 2.6 (r26:66721, Oct 2 2008, 11:35:03) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> from test import regrtest >>> regrtest.main() test_grammar test_opcodes test_dict test_builtin test_exceptions test_types test_unittest test_doctest test_doctest2 test_MimeWriter test_SimpleHTTPServer test_StringIO test___all__ test___future__ test__locale test__locale skipped -- cannot import name RADIXCHAR test_abc test_abstract_numbers test_aepack test_aepack skipped -- No module named aepack test_al test_al skipped -- No module named al test_anydbm test_applesingle test_applesingle skipped -- No module named macostools test_array test_ast test_asynchat test_asyncore test_atexit test_audioop test_augassign test_base64 test_bastion test_bigaddrspace test_bigmem test_binascii test_binhex test_binop test_bisect test test_bisect failed -- Traceback (most recent call last): File "C:\Python26\Lib\test\test_bisect.py", line 208, in test_listDerived self.assertEqual([5, 10], lst.data) AssertionError: [5, 10] != [] test_bool test_bsddb test_bsddb185 test_bsddb185 skipped -- No module named bsddb185 test_bsddb3 test_bsddb3 skipped -- Use of the `bsddb' resource not enabled test_buffer test_bufio test_bytes test test_bytes failed -- Traceback (most recent call last): File "C:\Python26\Lib\test\test_bytes.py", line 732, in test_copied self.assertFalse(x is x.translate(t)) AssertionError test_bz2 test_calendar test_call test_capi test_cd test_cd skipped -- No module named cd test_cfgparser test_cgi test_charmapcodec test_cl test_cl skipped -- No module named cl test_class test_cmath test_cmd test_cmd_line test_cmd_line_script test_code test_codeccallbacks test_codecencodings_cn test_codecencodings_hk test_codecencodings_jp test_codecencodings_kr test_codecencodings_tw test_codecmaps_cn test_codecmaps_cn skipped -- Use of the `urlfetch' resource not enabled test_codecmaps_hk test_codecmaps_hk skipped -- Use of the `urlfetch' resource not enabled test_codecmaps_jp test_codecmaps_jp skipped -- Use of the `urlfetch' resource not enabled test_codecmaps_kr test_codecmaps_kr skipped -- Use of the `urlfetch' resource not enabled test_codecmaps_tw test_codecmaps_tw skipped -- Use of the `urlfetch' resource not enabled test_codecs test_codeop test_coding test_coercion test_collections test_colorsys test_commands test_commands skipped -- Not posix; skipping test_commands test_compare test_compile test_compiler test_complex test_complex_args test_contains test_contextlib test_cookie test_cookielib test_copy test_copy_reg test_cpickle C:\Documents and Settings\cjw\Desktop>

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