[Tim]
Anyone remember why setdefault's second argument is optional?
IIRC, this is a vestige from its ancestor. The proposal for setdefault() described it as behaving like dict.get() but inserting the key if not found.
Haven't found any 1-arg uses of setdefault() either, except for test code verifying that you _can_ omit the second arg.
Likewise, I found zero occurrences in the library, in my cumulative code base, and in the third-party packages on my system.
If there isn't a sane use case for leaving the second argument out, I'd like to drop the possibility in P3K (assuming setdefault() survives).
Give a lack of legitimate use cases, do we have to wait to Py3.0? It could likely be fixed directly and not impact any code that people care about. Raymond