[Python-Dev] breaking list.append()

[Guido van Rossum]

> 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/)