Mailman 3 November 2009 - Python-Dev

Re: [Python-Dev] 2.7 Release? 2.7 == last of the 2.x line?
by Larry Bugbee 05 Nov '09

05 Nov '09

This is my problem to solve... I work with a lot of [non-production] crypto where byte strings are a normal way of manipulating and storing keys and other artifacts. Under Python2 I have few/no Unicode issues. With Python3's default string type being Unicode, there are a lot of subtle ways where my codes go south. Like I say, it is my problem. I will convert to Py3, but not likely before summer. Besides 2to3, any other tools/suggestions would be welcome. (Perhaps there is a Master switch to disable Unicode? ;-) Changing the subject... I say -1 on backporting more 3.x features to 2.6/2.7. As previously mentioned, leave the carrot. And best intentions aside, backports can introduce problems of their own.

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PyCon 2010: Poster sessions
by Aahz 04 Nov '09

04 Nov '09

PyCon 2010: Poster sessions =============================================================== Due date: November 30, 2009 PyCon 2010 introduces a new type of presentation, the poster session. Poster sessions consist of two pieces: * A display space where you can put up information about a topic * Live Q&A during a plenary timeslot where people can get more information from you while you stand next to your display For more information and to submit a poster proposal, visit http://us.pycon.org/2010/conference/posters/ -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ [on old computer technologies and programmers] "Fancy tail fins on a brand new '59 Cadillac didn't mean throwing out a whole generation of mechanics who started with model As." --Andrew Dalke

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PEP 382: Namespace Packages
by "Martin v. Löwis" 04 Nov '09

04 Nov '09

I propose the following PEP for inclusion to Python 3.1. Please comment. Regards, Martin Abstract ======== Namespace packages are a mechanism for splitting a single Python package across multiple directories on disk. In current Python versions, an algorithm to compute the packages __path__ must be formulated. With the enhancement proposed here, the import machinery itself will construct the list of directories that make up the package. Terminology =========== Within this PEP, the term package refers to Python packages as defined by Python's import statement. The term distribution refers to separately installable sets of Python modules as stored in the Python package index, and installed by distutils or setuptools. The term vendor package refers to groups of files installed by an operating system's packaging mechanism (e.g. Debian or Redhat packages install on Linux systems). The term portion refers to a set of files in a single directory (possibly stored in a zip file) that contribute to a namespace package. Namespace packages today ======================== Python currently provides the pkgutil.extend_path to denote a package as a namespace package. The recommended way of using it is to put:: from pkgutil import extend_path __path__ = extend_path(__path__, __name__) int the package's ``__init__.py``. Every distribution needs to provide the same contents in its ``__init__.py``, so that extend_path is invoked independent of which portion of the package gets imported first. As a consequence, the package's ``__init__.py`` cannot practically define any names as it depends on the order of the package fragments on sys.path which portion is imported first. As a special feature, extend_path reads files named ``*.pkg`` which allow to declare additional portions. setuptools provides a similar function pkg_resources.declare_namespace that is used in the form:: import pkg_resources pkg_resources.declare_namespace(__name__) In the portion's __init__.py, no assignment to __path__ is necessary, as declare_namespace modifies the package __path__ through sys.modules. As a special feature, declare_namespace also supports zip files, and registers the package name internally so that future additions to sys.path by setuptools can properly add additional portions to each package. setuptools allows declaring namespace packages in a distribution's setup.py, so that distribution developers don't need to put the magic __path__ modification into __init__.py themselves. Rationale ========= The current imperative approach to namespace packages has lead to multiple slightly-incompatible mechanisms for providing namespace packages. For example, pkgutil supports ``*.pkg`` files; setuptools doesn't. Likewise, setuptools supports inspecting zip files, and supports adding portions to its _namespace_packages variable, whereas pkgutil doesn't. In addition, the current approach causes problems for system vendors. Vendor packages typically must not provide overlapping files, and an attempt to install a vendor package that has a file already on disk will fail or cause unpredictable behavior. As vendors might chose to package distributions such that they will end up all in a single directory for the namespace package, all portions would contribute conflicting __init__.py files. Specification ============= Rather than using an imperative mechanism for importing packages, a declarative approach is proposed here, as an extension to the existing ``*.pkg`` mechanism. The import statement is extended so that it directly considers ``*.pkg`` files during import; a directory is considered a package if it either contains a file named __init__.py, or a file whose name ends with ".pkg". In addition, the format of the ``*.pkg`` file is extended: a line with the single character ``*`` indicates that the entire sys.path will be searched for portions of the namespace package at the time the namespace packages is imported. Importing a package will immediately compute the package's __path__; the ``*.pkg`` files are not considered anymore after the initial import. If a ``*.pkg`` package contains an asterisk, this asterisk is prepended to the package's __path__ to indicate that the package is a namespace package (and that thus further extensions to sys.path might also want to extend __path__). At most one such asterisk gets prepended to the path. extend_path will be extended to recognize namespace packages according to this PEP, and avoid adding directories twice to __path__. No other change to the importing mechanism is made; searching modules (including __init__.py) will continue to stop at the first module encountered. Discussion ========== With the addition of ``*.pkg`` files to the import mechanism, namespace packages can stop filling out the namespace package's __init__.py. As a consequence, extend_path and declare_namespace become obsolete. It is recommended that distributions put a file <distribution>.pkg into their namespace packages, with a single asterisk. This allows vendor packages to install multiple portions of namespace package into a single directory, with no risk of overlapping files. Namespace packages can start providing non-trivial __init__.py implementations; to do so, it is recommended that a single distribution provides a portion with just the namespace package's __init__.py (and potentially other modules that belong to the namespace package proper). The mechanism is mostly compatible with the existing namespace mechanisms. extend_path will be adjusted to this specification; any other mechanism might cause portions to get added twice to __path__. Copyright ========= This document has been placed in the public domain.

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language summit topic: issue tracker
by Brett Cannon 03 Nov '09

03 Nov '09

Another summit, another potential time to see if people want to change anything about the issue tracker. I would bring up: - Dropping Stage in favor of some keywords (e.g. 'needs unit test', 'needs docs') - Adding a freestyle text box to delineate which, if any, stdlib module is the cause of a bug and tie that into Misc/maintainers.rst; would potentially scale back the Component box -Brett

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thanks to everyone cleaning up the tests
by Brett Cannon 03 Nov '09

03 Nov '09

Just wanted to publicly thank everyone who has been causing all the checkins to fix and stabilize the test suite (I think it's mostly Antoine and Mark, but I could be missing somebody; I'm under a deadline so only have marginal higher brain functionality). -Brett

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A new way to configure logging
by Vinay Sajip 02 Nov '09

02 Nov '09

At present, configuration of Python's logging package can be done in one of two ways: 1. Create a ConfigParser-readable configuration file and use logging.config.fileConfig() to read and implement the configuration therein. 2. Use the logging API to programmatically configure logging using getLogger(), addHandler() etc. The first of these works for simple cases but does not cover all of the logging API (e.g. Filters). The second of these provides maximal control, but besides requiring users to write the configuration code, it fixes the configuration in Python code and does not facilitate changing it easily at runtime. In addition, the ConfigParser format appears to engender dislike (sometimes strong dislike) in some quarters. Though it was chosen because it was the only configuration format supported in the stdlib at that time, many people regard it (or perhaps just the particular schema chosen for logging's configuration) as 'crufty' or 'ugly', in some cases apparently on purely aesthetic grounds. Recent versions of Python of course support an additional battery-included format which can be used for configuration - namely, JSON. Other options, such as YAML, are also possible ways of configuring systems, Google App Engine-style, and PyYAML has matured nicely. There has also been talk on the django-dev mailing list about providing better support for using Python logging in Django. When it happens (as of course I hope it does) this has the consequence that many new users who use Django but are relatively inexperienced in Python (e.g. in PHP shops which are moving to Django) will become exposed to Python logging. As Django is configured using a Python module and use of ConfigParser-style files is not a common approach in that ecosystem, users will find either of the two approaches outlined above a particular pain point when configuring logging for their Django applications and websites, unless something is done to avoid it. All three of the contenders for the title of "commonly found configuration mechanism" - JSON, YAML and Python code - will be expressible, in Python, as Python dicts. So it seems to make sense to add, to logging.config, a new callable bound to "dictConfig" which will take a single dictionary argument and configure logging from that dictionary. An important facet of implementing such a scheme will be the format or schema which the dictionary has to adhere to. I have started working on what such a schema would look like, and if people here think it's a good idea to go ahead with this, I'll provide the details of the schema on a separate post which I'll also cross-post on comp.lang.python so that I can get feedback from there, too. In outline, the scheme I have in mind will look like this, in terms of the new public API: class DictConfigurator: def __init__(self, config): #config is a dict-like object (duck-typed) import copy self.config = copy.deepcopy(config) def configure(self): # actually do the configuration here using self.config dictConfigClass = DictConfigurator def dictConfig(config): dictConfigClass(config).configure() This allows easy replacement of DictConfigurator with a suitable subclass where needed. What's the general feeling here about this proposal? All comments and suggestions will be gratefully received. Regards, Vinay Sajip

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Possible language summit topic: buildbots
by Mark Dickinson 02 Nov '09

02 Nov '09

Would it be worth spending some time discussing the buildbot situation at the PyCon 2010 language summit? In the past, I've found the buildbots to be an incredibly valuable resource; especially when working with aspects of Python or C that tend to vary significantly from platform to platform (for me, this usually means floating-point, and platform math libraries, but there are surely many other things it applies to). But more recently there seem to have been some difficulties keeping a reasonable number of buildbots up and running. A secondary problem is that it can be awkward to debug some of the more obscure test failures on buildbots without having direct access to the machine. From conversations on IRC, I don't think I'm alone in wanting to find ways to make the buildbots more useful. So the question is: how best to invest time and possibly money to improve the buildbot situation (and as a result, I hope, improve the quality of Python)? What could be done to make maintenance of build slaves easier? Or to encourage interested third parties to donate hardware and time? Are there good alternatives to Buildbot that might make a difference? What do other projects do? These are probably the wrong questions; I'm hoping that a discussion would help produce the right questions, and possibly some answers. Mark

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Integer behaviour in Python 2.6.4
by Sturla Molden 02 Nov '09

02 Nov '09

Why does this happen? >>> type(2**31-1) <type 'long'> It seems to have broken NumPy's RNG on Win32.

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Bizarre mtime behaviour
by Antoine Pitrou 01 Nov '09

01 Nov '09

Hello, I wondered if someone had a clue about the following behaviour. While debugging an erratic test_mailbox failure on RDM's buildbot (and other machines), it turned out that the system sometimes set the wrong mtime on a directory: $ date && python -c 'import os; os.link("setup.py", "t/c")' && stat t && date Sun Nov 1 09:49:04 EST 2009 File: `t' Size: 144 Blocks: 0 IO Block: 4096 directory Device: 811h/2065d Inode: 223152 Links: 2 Access: (0755/drwxr-xr-x) Uid: ( 1001/ pitrou) Gid: ( 1005/ pitrou) Access: 2009-11-01 09:10:11.000000000 -0500 Modify: 2009-11-01 09:49:03.000000000 -0500 Change: 2009-11-01 09:49:03.000000000 -0500 Sun Nov 1 09:49:04 EST 2009 As you see above, the mtime for directory 't' is set to a full second before the actual modification has happened. Sprinkling traces of time.time() and os.path.getmtime() on Lib/mailbox.py shows this is exactly what trips up test_mailbox. I've got posted a patch to fix it (see issue #6896), but I would like to know if such OS behaviour is normal. Regards Antoine.

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