[Zope3-dev] interface conventions: default=_RAISE_ERROR

[Barry A. Warsaw]

>>>>> "GvR" == Guido van Rossum <guido@python.org> writes:

    GvR> I think you're going too far here.  While it's sometimes
    GvR> inconvenient that getattr() raises an exception (I think that
    GvR> maybe 50% of the occurrences in the standard library are
    GvR> surrounded by a try/except), the customary default of None
    GvR> really doesn't work for getattr(), because it's a legal
    GvR> value.  dict.get() is different because it is specifically
    GvR> intended to provide a default, and the dict[key] notation is
    GvR> available for when the exception is okay.

Good point.

    GvR> What's wrong with getattr() is that it raises an exception
    GvR> with 2 arguments but returns a default with 3 arguments, and
    GvR> that's the pattern we're trying to stomp out here -- not the
    GvR> idea that accessors can raise exceptions.

So if you had to do it over again, what would the signature/semantics
of getattr() be?

-Barry