Setting default_factory of defaultdict to key

[Shiyao Ma]

On Dec 07 at 11:31 -0500, Dave Angel wrote:
> Since this clearly is intended to be part of the earlier thread, please make
> it so by using reply-list or whatever equivalent your email program has.

Kinda OT. But interested what's the difference between reply-list and to.
In addition, based on what information a thread is formed?

-- 
Shiyao Ma
http://introo.me