The next version of Django (Python's largest web framework) will experimentally support Python 3.0 next release. They did so because maintaining two branches wo

The next version of Django (Python's largest web framework) will experimentally support Python 3.0 next release. They did so because maintaining two branches would be a pain, and they didn't want to dump their existing community. Not too long ago, matplotlib (the plotting library) didn't have ports for some versions. They were slow to port because they were waiting for scipy and numpy. Anything which deals heavily in string processing needs a major re-write. Libraries were waiting for other libraries, which where waiting for other libraries to be ported. If Rails didn't support Ruby 1.9, I'd imagine the migration would have been slower.