Steven D'Aprano writes:
> What would this do?
>
> def __init__(self, spam.x, eggs.y): pass
>
> How about this?
>
> def __init__(self, x, x.y): pass
IMO, both of those should be errors. This syntax only makes much
sense for the first formal argument of a method definition, because
it's the only formal argument which has a fixed definition. The form
"def foo(self, x, x.y)" has an interpretation, I guess, but
def foo(self, x, y):
x.y = y
is not a pattern I can recall ever seeing, and it could be relatively
easily relaxed if it were requested enough. On the other hand, folks
do frequently request a way to DRY out long suites of "self.x = x"
assignments.
This could, of course, be done with a symbol such as '@' or even '.',
but '@' could also be used for other purposes (late binding, for
example), and "def foo(self, .x, .y):" looks like both grit on Tim's
screen and a typo. On the other hand, I can't imagine what else might
be meant by "def foo(self, self.x):".
All that said, I'm not a fan of this feature as such. But giving this
semantics to formal arguments of the form "self.x" is the most
intuitive (in the sense of "hard to give another interpretation") of
the proposals I've seen.
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