Jay Parlar wrote:
[...]
> >> getattr(obj "foo" + "bar")().
[...vs...]
> > meth = getattr(self.visitor, 'visit' + className, 0)
[...]
> I don't think you understood my assertion, then. The example that the
> original poster gave was using getattr() with a simple string ("foo" +
> "bar") for the 'name' argument, and without a default return value (as
> opposed to throwing a variable in there, or a string plus a variable
> like you did, or a default retval).
Whether you evaluate the attribute lookup and immediately call the
value returned, or whether you instead hold on to that value and invoke
it later, is fairly unimportant when considering the behaviour of the
program, but such distinctions are important if you wish to acknowledge
the extent to which "dynamic" behaviour permeates running Python
programs, especially if you're interested in analysing their behaviour
at compile time.
> I even said you can do some "very powerful things" with getattr, by
> which I meant something exactly like you did. What did you think I
> meant by that?
Exactly what I gave as an example. The original example was just badly
formulated: two string literals glued together doesn't really capture
the imagination. I doubt that many compiler writers and IDE makers
seeking to improve their respective code generation and tooltip-popping
experiences would make the handling of such contrived examples a
priority - the possibilities presented by the general underlying
mechanisms would be far more worrying.
Paul
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