[wonderzombie]

I'm guessing you can't really do a 1:1, although maybe the OP can clarify.

They do stuff like this in jQuery, so I can't imagine it's all that difficult in Python.

My initial thought would be to write something analogous to Maybe. You can't pattern match in Python, which is a shame, but you could make it so that foo.bar().baz().quux() will return MaybeResult, which everything involved in the transaction inherits from. MaybeResult might have a "success" variable on it indicating whether it ought to be treated as Nothing. Otherwise, check "result."

This is naive but it gets you a little bit closer to fault-tolerant chaining of interdependent methods. Not as nice as Haskell, obvs. :)

[sznurek]

I wrote 'monad-inspired' structure because of lack of syntactic sugar (do notation). So it basically looks like that:

  login_action = Write('PASS') >> \
                 Read('pass') >> \
                 Guard(lambda v: v['pass'] == 'mysecret') >> \
                 Write('WELCOME')
  
  register(socket, login_action, on_success=func1, on_error=func2)

Of course you can develop this idea futher:

  cat = Read('line') >> Write(lambda v: v['line'])
  cat.append_action(cat)

  register(socket, cat, on_error=handle_error_cb)

[edwkar]

Nice!!