Hi Tristan

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"Tristan" == Tristan Seligmann <mithrandi@mithrandi.net> writes: Tristan> You can, however, encapsulate it into a classmethod or free Tristan> function that you call to get an instance of MyClass. This is a Tristan> pattern often seen when there are various ways to build an Tristan> instance of some class; you'll have a very basic __init__, and Tristan> then a bunch of factory functions or classmethods that do more Tristan> complicated work before passing the results in to the class's Tristan> constructor.

OK, thanks. It feels to me (please correct me if I'm wrong) that the main reason you'd want to follow this pattern is because you can't deal with Deferreds in an __init__ method. If you weren't dealing with Deferreds, you could just pass args to __init__ and have it figure out what to do. While it might be simpler to do as you describe, and have various external factories, it feels (to me anyway) like you're taking behavior that's class-dependent and putting it outside the class. __init__ can't return a result, presumably because if it has something it wants to remember, or give you access to, it can put it on self, provide you with a method, etc. But in the Twisted world, I think it makes sense that there is some provision for what's essentially a two-phase __init__. I quite like my approach, because the programmer wanting to write "normal" Twisted code will likely find it natural that __init__ could work with Deferreds, including returning one. To me that feels very natural. Having said that, I don't particularly like the fact that there's a special-case metaclass creating my classes, even though I wrote the code myself :-)

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BTW, I sometimes have the feeling that Deferreds are like how M$ characterizes the GPL. Viral. Once you call anything creating a Deferred, you're hooked - whatcha gonna do with that Deferred boy? Take one sip of the Deferred Kool Aid and the next thing you know you're on a drip.

Tristan> Just wait until you start trying to combine iterators and deferreds ;) Oh yeah... I tried that too :-) http://www.twistedmatrix.com/pipermail/twisted-python/2008-June/017984.html Comments on that code very welcome too! Terry