[Twisted-Python] Thoughts on Deferred

[Itamar Shtull-Trauring]

On Thu, 6 Mar 2003 06:02:23 +0000
"Clark C. Evans" <cce at clarkevans.com> wrote:

>   2.  The error handling could use help.  The cross-over behavior,
>       while unique, doesn't provide any more value over a simple 
>       stack /w state flag (good/bad) attach to each callback.

Look again :)

In fac, the cross-over behaviour is designed to mimic Python's
try/except semantics in a callback oriented way. And exceptions are
*useful*.

 try:
     x = foo(2)
 except FooError:
     x = None

becomes:

 d = foo(2)
 def err(f):
     f.trap(FooError)
     return None
 d.addErrback(err).addCallback(gotX)