On Fri, Feb 1, 2013 at 3:58 AM, Guido van Rossum <guido@python.org> wrote:
hasattr() smells bad. It also has namespace issues (hasattr(transport, "write") returns true) and if people forget to use it (perhaps because the transport they normally use always has a certain attribute) their code is brittle. Defining a new API with a string key signals clearly that the value may or may not exist, and reminds people to test the result for None. (Of course they can forget that too. But it still feels different to me.)
I understand. It's a good solution for clearly separating the standard transport api from the extra-and-specific api. We want to make it obvious when a protocol is breaking the transport abstraction - to promote playing nicely with different transports.