Based on this python-3000 thread and a number of off-list emails, I’m dropping my earlier objection to PEP 3107. I hadn’t been convinced that there was a sufficiently broad spectrum of use-cases for function annotations to justify changing Python’s syntax. A bunch of people came out of the woodwork with viable uses for annotations, which is what I was looking for. Accordingly, I’ll be working up a patch to PEP 3107 to include a “Use Cases” section.

Thanks to everyone who emailed or commented, especially Phillip J. Eby, who led the python-3000 effort to convince me.