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0 pointslvh13y ago0 comments

Your restricted environments don't allow virtualenvs?

It's interesting that inheritance vs composition comes up, since one of the most common criticisms I've heard is actually the opposite (that there's too many different objects to get things done).

However, I do understand why you might think this: protocols, which is probably the first thing you touch in Twisted, are usually implemented through inheritance. For resources, the default implementation that you subclass (twisted.web.resource.Resource) contains a bunch of behavior that you almost certainly want.

The important thing to remember is that this inheritance is only to get default behavior. If you want to implement it without inheritance, Twisted very clearly and explicitly defines the interface you have to implement:

https://twistedmatrix.com/documents/current/api/twisted.inte...

https://twistedmatrix.com/documents/current/api/twisted.web....

These are just two examples: Interfaces are all over twisted.

And, to quote from the article:

  It doesn't need to be that way, though.  When you create
  an object, it is best to create it as independently as
  possible; to test it in isolation; to discretely separate
  its every interaction with the outside world so that they
  may be carefully controlled, monitored, intercepted an
  inspected, one iteration at a time.

This has recently come up in the async-pep conversation on Python-ideas. If you have a significantly better solution for e.g LineReceiver, I'd love to steal it!

0 comments

cturner13y ago

Thanks for feedback. #twisted ppl were very helpful to me in the early days of me learning about network programming and python.

I'm impressed with the achievement of Twisted. For example, the way it offers support for both unix-way async (select, getabyte getabyte), and the Windows/AIX alternative where you can make a system call that says "get back to me when you have a complete message that I can consume in one hit". It'll be way faster and more polished than the stuff I write too.

Part of the reason there's so many objects in it is because it does so damn much - there's support for all sorts of existing protocols in twisted. And - a powerful framework can't entirely abstract away the layering. If it does, it stops being powerful.

It might be possible to use virutalenvs. I keep meaning to look into these. I am skeptical of frameworks though. You become vulnerable to version changes, you can't take knowledge to a new platform.

Very interested to see something from the python-ideas conversation in the standard library. I'll have a serious go at whatever they end up with, and wouldn't mind if it was a stripped down twisted but with composition rather than inheritance. It may be the feature that pushes python people to v3. I'll look over the links you sent regarding this.

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