Mailman 3 October 2007 - Python-Dev

Declaring setters with getters
by Guido van Rossum Nov. 10, 2007

Nov. 10, 2007

I've come up with a relatively unobtrusive pattern for defining setters. Given the following definition: def propset(prop): assert isinstance(prop, property) def helper(func): return property(prop.__get__, func, func, prop.__doc__) return helper we can declare getters and setters as follows: class C(object): _encoding = None @property def encoding(self): return self._encoding @propset(encoding) def encoding(self, value=None): if … [View More]

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Request for inclusion in 2.5.2 (5-for-1)
by Mike Klaas Nov. 7, 2007

Nov. 7, 2007

Issue http://bugs.python.org/issue1663329 details an annoyance in the subprocess module that has affected several users, including me. Essentially, closing hundreds of thousands of file descriptors by round-tripping through the python exception machinery is very slow, taking hundreds of milliseconds and at times many seconds. The proposed fix is to write this loop in c. The c function is but a handful of lines long. I purposefully kept the implementation trivial so that it … [View More]

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Special file "nul" in Windows and os.stat
by Facundo Batista Nov. 7, 2007

Nov. 7, 2007

Hi, people! I'm following the issue 1311: http://bugs.python.org/issue1311 There (and always talking in windows), the OP says the in Py2.4 os.path.exists("nul") returned True and now in 2.5 returns False. Note that "nul" is an special file, something like /dev/null. We made some tests, and we have inconsisten behaviour in previous Python versions. For example, in Py2.3.5 in my machine I get a False, as in Py2.5. But other person in the bug, gets True in 2.3.3 and False in 2.5. Even the OP … [View More]

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Does Python need a file locking module (slightly higher level)?
by skip＠pobox.com Nov. 3, 2007

Nov. 3, 2007

I'm always daunted by the prospect of trying to implement file locking. This just came up again in SpamBayes where we have never protected our pickle files from corruption when multiple processes access them simultaneously. The presence of networked file systems and platform-independent locks make it a nasty little problem. Maybe I'm just showing my age. Does fcntl.flock work over NFS and SMB and on Windows? If this is still as much of a mess as I remember, should Python provide a simple … [View More]

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Re: [Python-Dev] Declaring setters with getters
by Phillip J. Eby Nov. 2, 2007

Nov. 2, 2007

At 11:09 AM 10/31/2007 -0700, Guido van Rossum wrote: >Yes, though I think that if prop.fdel is None, we could use func in >both slots. Eh? Isn't prop.fdel supposed to be a single-argument function? ISTM that C is the only place where fset and fdel are the same thing.

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Re: [Python-Dev] Declaring setters with getters
by Raymond Hettinger Nov. 2, 2007

Nov. 2, 2007

> I'd like to make this [propset] a standard built-in, +1 -- I find this to be an attractive syntax > I'd also like to change property so that the doc > string defaults to the doc string of the getter. +1 -- This should also be done for classmethod, staticmethod, and anything else that wraps functions. Alternatively, the doc string could be made a little more informative: __doc__ = 'property of function %s: %s' % (f.__name__, f.__doc__) Raymond

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Re: [Python-Dev] Declaring setters with getters
by Raymond Hettinger Nov. 2, 2007

Nov. 2, 2007

> I'm not sure about the name "propset" ... >Maybe something like "setproperty" would be better. I think not. Saying "setproperty" has too many ambiguous mental parsings. When does "set" take place -- assigning a value to a property is different defining the property itself. Is "set" a verb so that we're talking about a property of sets/frozensets. Is "set" a completed action so that the property has been set. Let's stick with "propset" which has precedent as an svn action and … [View More]

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ctypes and libffi
by Thomas Heller Oct. 31, 2007

Oct. 31, 2007

The ctypes sources contain the source code for libffi, in Modules/_ctypes/libffi. These sources were pulled from GCC cvs some time ago, and a new configure system was written by Perky iirc. Now, it seems that these sources are showing their age and a newer libffi version should be used instead. There are issues on certain platforms like mips64, arm, armeabi; also on other systems to correctly use the c_longdouble data type that I added recently. See also http://bugs.python.org/issue1292. … [View More]

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Re: [Python-Dev] Declaring setters with getters
by Raymond Hettinger Oct. 31, 2007

Oct. 31, 2007

> and have a matching propdel decorator? -1. That would be a complete waste of builtin space. Put stuff in when it is really needed. Ideas are not required to automatically propagate from the commonly used cases to the rarely used cases. Raymond

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Re: [Python-Dev] Declaring setters with getters
by Phillip J. Eby Oct. 31, 2007

Oct. 31, 2007

At 10:08 AM 10/31/2007 -0700, Guido van Rossum wrote: >I've come up with a relatively unobtrusive pattern for defining >setters. Given the following definition: > >def propset(prop): > assert isinstance(prop, property) > def helper(func): > return property(prop.__get__, func, func, prop.__doc__) > return helper Shouldn't that be property(prop.fget, func, prop.fdel, prop.__doc__), and have a matching propdel decorator? Apart from those extremely … [View More]

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