Software configuration management is HARD. Every sudden backwards incompatible change (warranted or not) makes it harder. Mutli-arg append is not hurting anyone as much as a sudden change to it would. It would be better to leave append() alone and publicize its near-term removal rather than cause random, part-time supported modules to stop working because their programmers may be too busy to update them right now.
I'm tired of this rhetoric. It's not like I'm changing existing Python installations retroactively. I'm planning to release a new version of Python which no longer supports certain long-obsolete and undocumented behavior. If you maintain a non-core Python module, you should test it against the new release and fix anything that comes up. This is why we have an alpha and beta test cycle and even before that the CVS version. If you are a Python user who depends on a 3rd party module, you need to find out whether the new version is compatible with the 3rd party code you are using, or whether there's a newer version available that solves the incompatibility. There are people who still run Python 1.4 (really!) because they haven't upgraded. I don't have a problem with that -- they don't get much support, but it's their choice, and they may not need the new features introduced since then. I expect that lots of people won't upgrade their Python 1.5.2 to 1.6 right away -- they'll wait until the other modules/packages they need are compatible with 1.6. Multi-arg append probably won't be the only reason why e.g. Digital Creations may need to release an update to Zope for Python 1.6. Zope comes with its own version of Python anyway, so they have control over when they make the switch. --Guido van Rossum (home page: http://www.python.org/~guido/)