[Python-Dev] Community buildbots (was Re: User's complaints) (original) (raw)

glyph at divmod.com glyph at divmod.com
Thu Jul 13 20:03:22 CEST 2006

On Wed, 12 Jul 2006 10:30:17 +1000, Michael Ellerman <michael at ellerman.id.au> wrote:

Well here's one I stumbled across the other day. I don't know if it's legit, but it's still bad PR:

http://www.gbch.net/gjb/blog/software/discuss/python-sucks.html

Having been exhorted (or maybe I mean "excoriated") by your friendly release manager earlier this week to post my comments and criticisms about Python here rather than vent in random IRC chatter, I feel morally compelled to comment.

I see some responses to that post which indicate that the specific bug will be fixed, and that's good, but there is definitely a pattern he's talking about here, not just one issue. I think there is a general pattern of small, difficult to detect breakages in Python. Twisted (and the various other Divmod projects that I maintain) are thoroughly unit-tested, but there are still significant issues in each Python release that require changes.

Unlike the jerk who posted that "python sucks" rant, I'm not leaving Python because one function changed in a major release; I do expect to have to maintain my projects myself, and major releases are "major" for a reason. I only wish that upgrading all my other dependencies were as easy as upgrading Python! I do see that the developers are working with some caution to avoid breaking code, and attempting to consider the cost of each change.

However, although I've seen lots of discussions of what "average" code might break when exposed to new versions of Python, these discussions tend to be entirely hypothetical. Do the core Python developers typically run the test suites of major Python applications when considering major changes, such as Zope, Plone, TurboGears, and of course Twisted? Not that breakages would be considered unacceptable -- some gain is surely worth the cost -- but to establish some empirical level of burden on the community?

I would like to propose, although I certainly don't have time to implement, a program by which Python-using projects could contribute buildslaves which would run their projects' tests with the latest Python trunk. This would provide two useful incentives: Python code would gain a reputation as generally well-tested (since there is a direct incentive to write tests for your project: get notified when core python changes might break it), and the core developers would have instant feedback when a "small" change breaks more code than it was expected to.

I can see that certain Python developers expect that some of this work is the responsibility of the user community, and to some extent that's true, but at least half of the work needs to be done before the changes are made. If some Python change breaks half of Twisted, I would like to know about it in time to complain about the implementation, rather than flailing around once the Python feature-freeze has set in and hoping that it's nothing too serious. For example, did anyone here know that the new-style exceptions stuff in 2.5 caused hundreds of unit-test failures in Twisted? I am glad the change was made, and one of our users did catch it, so the process isn't fatally broken, but it is still worrying.

Another problem is simply that the Python developers don't have the same very public voice that other language developers do. It doesn't necessarily have to be a blog, but python-dev is fast-paced and intimidating, and a vehicle for discussion among those in the know, rather than dissimenation to the community at large. It's a constant source of anxiety to me that I might miss some key feature addition to Python which breaks or distorts some key bit of Twisted functionality (as the new-style exceptions, or recent ImportWarning almost did) because I don't have enough time to follow all the threads here. I really appreciate the work that Steve Bethard et. al. are doing on the python-dev summaries, but they're still pretty dry and low level.

While the new python.org is very nice, I do note that there's no "blogs" entry on the front page, something which has become a fixture on almost every other website I visit regularly. The news page is not very personal, mainly a listing of releases and events. There's no forum for getting the community excited about new features (especially new features which are explicitly enabled by potential breakages), and selling them on the cool uses. Who knows, maybe I'll even start using decorators syntax all over the place if I see them presented somewhere by someone who is very excited about the feature and thinks it's worthwhile, rather than as a defense on a mailing list against a criticism, or a simple announcement of the feature's existence.

I've seen the other side of this problem as well, so I can appreciate that it is quite difficult to get this kind of thing right: lots of applications using Twisted break when we change broken or deprecated APIs. Twisted is lucky though; it has numerous subprojects, and I maintain a half-dozen unrelated projects in a different repository. Twisted itself is a fairly representative "application using Twisted", so when something breaks "average" Twisted code, I know about it right away. Python is less an application using Python: the standard library is rather passive (there is no "end-to-end" application path to test, only individual functions and classes), and the test coverage of included Python modules is rather spotty.

I hope someone finds some of these suggestions helpful. I only wish I had the time and energy to act on some of them.

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