Advogato blog for movement

Writing Python Properly

Sat, 12 Jul 2008 14:10:33 GMT

What are people's approaches to writing Python correctly? The library documentation basically doesn't document the set of exceptions the routines can throw, which makes it very difficult to catch the right things, and do the right thing[1] (for example). What do people do to deal with this problem?

[1] on that note, if you're writing a command line tool in Python, please catch KeyboardInterrupt and exit quietly. Drives me crazy!

Bubble calendar

Thu, 10 Jul 2008 15:09:40 GMT

These are cool:

Nice bookends

Tue, 8 Jul 2008 22:06:27 GMT

Nice bookends:

Mercurial corruption (again)

Mon, 7 Jul 2008 04:06:59 GMT

It's somewhat disappoint that Mercurial is still corrupting repositories when you interrupt MQ operations.

Relatively easily recoverable for me this time, thankfully. I'd still like to see hg backup from the OpenSolaris SCM project get merged upstream though :)

Pure Python Plugins

Wed, 2 Jul 2008 03:07:04 GMT

After some searching and asking around I didn't find any good explanation of the simplest way to implement plugins in Python. So, for posterity's sake, here's my solution. I'm sure there's a better way: I'd love to hear your suggestions.

First, the requirements. The code cannot have knowledge of how the plugins are named (.so files, .py, package dirs, etc.). I don't want to hard-code the list of plugins, as this defeats its dynamic nature altogether. I have to be able to iterate across all plugins. Any user should be able to use the module without knowing that it's got plugins. Finally, it's got to be as simple as possible.

First up, we have whatever/__init__.py:


import pkgutil
import imp
import os

plugin_path = [os.path.join(__path__[0], "plugins/")]

for loader, name, ispkg in pkgutil.iter_modules(plugin_path):
    file, pathname, desc = imp.find_module(name, plugin_path)
    imp.load_module(name, file, pathname, desc)

This basically uses Python's module search to find all contents of the plugins sub-directory and load them. Now we have some more scaffolding in the same directory, as whatever/whatever.py:


plugins = []

class plugin(object):
   """Abstract plugin base class."""
   ...

def register_plugin(plugin)
    global plugins
    plugins += [ plugin ]

# utility functions to iterate across and use plugins...

Finally, each plugin looks something like this, in plugins/foo.py:


from whatever/whatever import *

class fooplugin(plugin):
    """Concrete class for foo plugin."""
    ...

register_plugin(fooplugin)

Simple enough, but it took a while to work it out. Unfortunately, it doesn't seem possible to merge whatever.py into __init__.py as we have a recursive import problem.

Cake of awesomeness

Thu, 19 Jun 2008 18:07:10 GMT

Best cake ever.

Amusing prank

Mon, 16 Jun 2008 22:10:56 GMT

An amusing prank. I love how they get back in, as if that'll somehow help.

Getting decent stack traces

Tue, 10 Jun 2008 23:13:53 GMT

Reading through this bug is seriously depressing to read (until Michael Matz steps in).
It was always complete madness to strip symbols from shipping binaries; it was always
madness to disable the frame pointer too. (The debuginfo trick is an excellent solution
to the problems of source-level debugging, by the way, it's just taken way, way, too far).

This is why you have to install a 1Gb debuginfo RPM in order to run OProfile on the kernel. Crazy.

It's a good read if you like to see certain people behaving like asshats to their fellow community
members too.

I Am Neurotic

Mon, 9 Jun 2008 16:14:42 GMT

My favourite quote from I Am Neurotic: "Everyday, at 7:47 am or pm, I always say Boeing, after the Airplane, and I don't know why. I've gotten into a lot of trouble, and I even say it in my sleep."

US TV

Fri, 6 Jun 2008 16:23:28 GMT

It's already extremely difficult to watch US TV, with adverts every 7 minutes, and massive animated
station idents taking up half the screen, but this is particularly obnoxious:

It's as if they want you not to watch.