[Twisted-Python] Deferred usage clarification

[Gary Poster]

Thanks for the quick reply!

Andrew Bennetts wrote:
> You're misunderstanding the purpose of Deferreds.  They don't do any magic
> to make blocking calls happen asynchronously.
...snip...
> 
> Does this make sense?

Yes.  Looks like deferToThread would be the simplest way to do what I 
want.  I wonder if you (or someone) would answer a similarly newbie-like 
follow up, though.

I see the pattern
   reactor.callLater(0, function)
a lot--this doesn't have thread semantics, though, so what is 
accomplished by specifying the 0 second delay?

Thanks again

Gary