I have tried a number of desktop feed aggregators, but I found that I liked
reading planets in Firefox best.
Recently, hearing all the buzz about DHTML applications taking over the world,
The result: Planet Mg now lets
you collapse stories you have read, and remembers collapsed stories in a
cookie. You can also move around stories with the keyboard (press ? for
a list of key bindings). There are also unit tests for the
Not everything works in Internet Explorer, though. I don't really need MSIE
compatibility on Planet Mg, as its intended audience is just one Firefox user (me), but it
would be a good exercise. I will work on it, time permitting.
I would like to thank Jeff Waugh, Scott James Remnant and other Planet
developers for Planet; Chris Dolan
planet; Edward Hieatt for JsUnit;
Peter-Paul Koch for QuirksMode.
They did it!
That's why I love Ubuntu and
forgive it such minor lapses as occasional kernel panics.
After all, I am running the unstable branch.
When you're developing a Zope 3 based application, and you want to make
old object databases continue to work as you change object attributes,
you should consider Zope 3 database generations.
proposal in the Zope 3 wiki describes the problem and possible
for the zope.app.generations package tells you about the internals. The
package is a real-world example of generations. This mini-article strives
to be a HOWTO.
This is a DRAFT version. I plan to show it to Zope 3
gurus, get feedback, and fix all bugs. After that, I will remove this
Here's how it works (slightly simplified): you tell Zope 3 the name of your
application, and the current generation number. Zope 3 stores this number in
the ZODB. Later, when you change your application, you will change the current
generation number and write a function that can upgrade existing data. On
every startup Zope 3 will check the current generation number with the number
stored in the ZODB for your application, and, if necessary, call your upgrade
So, you have a Zope 3 based application that is being used. You have worked
long and hard on new shining features, but before you release a newer version,
you want to make sure existing users can upgrade without losing any data. You
decide to use generations. How do you start?
Well, you should have declared that the old version of your application used
generation 0 long ago. However all is not lost, you can rectify that omission
without too much trouble. Add the following bit of ZCML into all Zope
instances that run the old version of your application:
Now restart that Zope 3 and go to
Make sure your application is shown there. Congratulations -- you have just
told your Zope that the old version of your application used database
generation 0. This is necessary if you want to write an upgrade script to
your new application version, which will be generation 1.
Create a new package, e.g. myapp.generations. This package
will contain the current version number and database upgrade scripts.
Create a __init__.py with the following contents:
from zope.app.generations.generations import SchemaManager
schemaManager = SchemaManager(
Create a evolve1.py with the following contents:
from zope.app.zopeappgenerations import getRootFolder
"""Upgrade myapp database from generation 0 to generation 1.
(describe database schema changes here)
root_folder = getRootFolder(context)
from zope.app.generations.utility import findObjectsProviding
for myobj in findObjectsProviding(root_folder, IMyAppObject):
myobj.newattribute = 42
from zope.app.generations.utility import findObjectsMatching
for myobj in findObjectsMatching(root_folder,
lambda ob: isinstance(ob, MyCppClass)):
myobj.newattribute = 42
Create a configure.zcml file with the following content:
Test the script with an old Data.fs file.
Now when you upgrade your application, Zope 3 will automatically run your
evolve function once.
Increment generation and minimum_generation in
__init__.py, and write a new evolveNUM.py module as
soon as you make a change to the database schema. Update the evolve function
as you continue evelopment, but freeze it when you make a new release.