Mailman 3 February 2006 - Python-Dev

Re: [Python-Dev] [Python-checkins] r42396 - peps/trunk/pep-0011.txt
by Neal Norwitz 21 Feb '06

21 Feb '06

[Moving to python-dev] I don't have a strong opinion. Any one else have an opinion about removing --with-wctype-functions from configure? n -- On 2/16/06, M.-A. Lemburg <mal(a)egenix.com> wrote: > neal.norwitz wrote: > > Author: neal.norwitz > > Date: Thu Feb 16 06:25:37 2006 > > New Revision: 42396 > > > > Modified: > > peps/trunk/pep-0011.txt > > Log: > > MAL says this option should go away in bug report 874534: > > > > The reason for the removal is that the option causes > > semantical problems and makes Unicode work in non-standard > > ways on platforms that use locale-aware extensions to the > > wc-type functions. > > > > Since it wasn't previously announced, we can keep the option until 2.6 > > unless someone feels strong enough to rip it out. > > I've been wanting to rip this out for some time now, but > you're right: I forgot to add this to PEP 11, so let's > wait for another release. > > OTOH, this normally only affects system builders, so perhaps > we could do this a little faster, e.g. add a warning in the > first alpha and then rip it out with one of the last betas ?! > > > Modified: peps/trunk/pep-0011.txt > > > > + Name: Systems using --with-wctype-functions > > + Unsupported in: Python 2.6 > > + Code removed in: Python 2.6

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bytes type discussion
by Guido van Rossum 21 Feb '06

21 Feb '06

I'm about to send 6 or 8 replies to various salient messages in the PEP 332 revival thread. That's probably a sign that there's still a lot to be sorted out. In the mean time, to save you reading through all those responses, here's a summary of where I believe I stand. Let's continue the discussion in this new thread unless there are specific hairs to be split in the other thread that aren't addressed below or by later posts. Non-controversial (or almost): - we need a new PEP; PEP 332 won't cut it - no b"..." literal - bytes objects are mutable - bytes objects are composed of ints in range(256) - you can pass any iterable of ints to the bytes constructor, as long as they are in range(256) - longs or anything with an __index__ method should do, too - when you index a bytes object, you get a plain int - repr(bytes[1,0 20, 30]) == 'bytes([10, 20, 30])' Somewhat controversial: - it's probably too big to attempt to rush this into 2.5 - bytes("abc") == bytes(map(ord, "abc")) - bytes("\x80\xff") == bytes(map(ord, "\x80\xff")) == bytes([128, 256]) Very controversial: - bytes("abc", "encoding") == bytes("abc") # ignores the "encoding" argument - bytes(u"abc") == bytes("abc") # for ASCII at least - bytes(u"\x80\xff") raises UnicodeError - bytes(u"\x80\xff", "latin-1") == bytes("\x80\xff") Martin von Loewis's alternative for the "very controversial" set is to disallow an encoding argument and (I believe) also to disallow Unicode arguments. In 3.0 this would leave us with s.encode(<encoding>) as the only way to convert a string (which is always unicode) to bytes. The problem with this is that there's no code that works in both 2.x and 3.0. -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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Memory Error the right error for coding cookie promise violation?
by bokr＠oz.net 21 Feb '06

21 Feb '06

Perhaps a more informative message would be nice. Here's an easy way to trigger it: >>> compile("#-*- coding: ascii -*-\nprint 'ab%c'\n"%0x80, '','exec') Traceback (most recent call last): File "<stdin>", line 1, in ? MemoryError Regards, Bengt Richter

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Proposal: defaultdict
by Jim Jewett 21 Feb '06

21 Feb '06

Adam Olsen asked: > ... d.getorset(key, func) would work in your use > cases? It is an improvement over setdefault, because it doesn't always evaluate the expensive func. (But why should every call have to pass in the function, when it is a property of the dictionary?) It doesn't actually *solve* the problem because it doesn't compose well. This makes it hard to use for configuration. (Use case from plucker web reader, where the config is arguably overdesigned, but ... the version here is simplified) There is a system-wide default config. Users have config files. A config file can be specified for this program run. In each of these, settings can be either general settings or channel-specific. The end result is that the value should be pulled from the first of about half a dozen dictionaries to have an answer. Because most settings are never used in most channels, and several channels are typically run at once, it feels wrong to pre-build the whole "anything they might ask" settings dictionary for each of them. On the other hand, I certainly don't want to write userchannelconfig.getorset(key, systemchannelconfig.getorset(key, ...) even once, let alone every time I get a config value. In other words, the program would work correctly if I passed in a normal but huge dictionary; I want to avoid that for reasons of efficiency. This isn't the only use for a mapping, but it is the only one I've seen where KeyError is "expected" by the program's normal flow. -jJ

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Re: [Python-Dev] defaultdict proposal round three
by Delaney, Timothy (Tim) 20 Feb '06

20 Feb '06

"Martin v. Löwis" wrote: > Delaney, Timothy (Tim) wrote: >> However, *because* Python uses duck typing, I tend to feel that >> subclasses in Python *should* be drop-in replacements. If it's not a >> drop-in replacement, then it should probably not subclass, but just >> use duck typing (probably by wrapping). > > Inheritance is more about code reuse than about polymorphism. Oh - it's definitely no hard-and-fast rule. owever, I have found that *usually* people (including myself) only subclass when they want an is-a relationship, whereas duck typing is behaves-like. In any case, Guido has produced a patch, and the tone of his message sounded like a Pronouncement ... Tim Delaney

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bdist_* to stdlib?
by Guido van Rossum 20 Feb '06

20 Feb '06

In private email, Phillip Eby suggested to add these things to the 2.5. standard library: bdist_deb, bdist_msi, and friends He explained them as follows: """ bdist_deb makes .deb files (packages for Debian-based Linux distros, like Ubuntu). bdist_msi makes .msi installers for Windows (it's by Martin v. Loewis). Marc Lemburg proposed on the distutils-sig that these and various other implemented bdist_* formats (other than bdist_egg) be included in the next Python release, and there was no opposition there that I recall. """ I guess bdist_egg should also be added if we support setuptools (not setuplib as I mistakenly called it previously)? (I'm still a bit unclear on the various concepts here, not having made a distribution of anything in a very long time...) -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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Simple CPython stack overflow.
by David Wilson 20 Feb '06

20 Feb '06

Just noticed this and wondered if it came under the Python should never crash mantra. Should sys.getrecursionlimit() perhaps be taken into account somewhere? >>> D = {'a': None} >>> for i in xrange(150000): ... D = {'a': D} ... >>> D {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': .... ': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {[+]'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a': {'a' .... Bus error bash$ Cheers, David. -- 'tis better to be silent and be thought a fool, than to speak and remove all doubt. -- Lincoln

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(-1)**(1/2)==1?
by Jonathan Barbero 20 Feb '06

20 Feb '06

Hello! My name is Jonathan, i´m new with Python. I try this in the command line: >>> (-1)**(1/2) 1 This is wrong, i think it must throw an exception. What do you think? Bye. Jonathan.

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Does eval() leak?
by John Marshall 20 Feb '06

20 Feb '06

Hi, Should I expect the virtual memory allocation to go up if I do the following? ----- raw = open("data").read() while True: d = eval(raw) ----- I would have expected the memory allocated to the object referenced by d to be deallocated, garbage collected, and reallocated for the new eval(raw) results, assigned to d. The file contains a large, SIMPLE (no self refs; all native python types/objects) dictionary (>300K). While doing 'd = eval(raw)' in the python interpreter I am monitoring the VIRT column of top and it keeps increasing until I run out of memory. When I use a safe_eval() from: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/364469 I have no memory problems. I see this under python 2.3.5 (fast and obvious). Thanks, John

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New Module: CommandLoop
by Crutcher Dunnavant 19 Feb '06

19 Feb '06

This is something I've been working on for a bit, and I think it is more or less ready to bring up on this list. I'd like to add a module (though probably not for 2.5). Before you ask, this module is _not_ compatible with cmd.py, as it is command oriented, whereas cmd.py is line oriented. Anyway, I'm looking for feedback, feature requests before starting the submission process. Code available here: http://littlelanguages.com/web/software/python/modules/cmdloop.py Base class for writing simple interactive command loop environments. CommandLoop provides a base class for writing simple interactive user environments. It is designed around sub-classing, has a simple command parser, and is trivial to initialize. Here is a trivial little environment written using CommandLoop: import cmdloop class Hello(cmdloop.commandLoop): PS1='hello>' @cmdloop.aliases('hello', 'hi', 'hola') @cmdloop.shorthelp('say hello') @cmdloop.usage('hello TARGET') def helloCmd(self, flags, args): ''' Say hello to TARGET, which defaults to 'world' ''' if flags or len(args) != 1: raise cmdloop.InvalidArguments print 'Hello %s!' % args[0] @cmdloop.aliases('quit') def quitCmd(self, flags, args): ''' Quit the environment. ''' raise cmdloop.HaltLoop Hello().runLoop() Here's a more complex example: import cmdloop class HelloGoodbye(cmdloop.CommandLoop): PS1='hello>' def __init__(self, default_target = 'world'): self.default_target = default_target self.target_list = [] @cmdloop.aliases('hello', 'hi', 'hola') @cmdloop.shorthelp('say hello') @cmdloop.usage('hello [TARGET]') def helloCmd(self, flags, args): ''' Say hello to TARGET, which defaults to 'world' ''' if flags or len(args) > 1: raise cmdloop.InvalidArguments if args: target = args[0] else: target = self.default_target if target not in self.target_list: self.target_list.append(target) print 'Hello %s!' % target @cmdloop.aliases('goodbye') @cmdloop.shorthelp('say goodbye') @cmdloop.usage('goodbye TARGET') def goodbyeCmd(self, flags, args): ''' Say goodbye to TARGET. ''' if flags or len(args) != 1: raise cmdloop.InvalidArguments target = args[0] if target in self.target_list: print 'Goodbye %s!' % target self.target_list.remove(target) else: print "I haven't said hello to %s." % target @cmdloop.aliases('quit') def quitCmd(self, flags, args): ''' Quit the environment. ''' raise cmdloop.HaltLoop def _onLoopExit(self): if len(self.target_list): self.pushCommands(('quit',)) for target in self.target_list: self.pushCommands(('goodbye', target)) else: raise cmdloop.HaltLoop HelloGoodbye().runLoop() -- Crutcher Dunnavant <crutcher(a)gmail.com> littlelanguages.com monket.samedi-studios.com

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