On 2021-12-06 11:21, Chris Angelico wrote:
On Tue, Dec 7, 2021 at 6:16 AM Brendan Barnwell <brenb...@brenbarn.net> wrote:
On 2021-12-05 08:14, Chris Angelico wrote:
> Closures cannot be executed without a context. Consider:
>
> def f(x=lambda: (a:=[])):
> if isinstance(x, FunctionType): x = x()
> print(a)
>
> Here's the problem: The name 'a' should be in the context of f, but
> that context*does not exist* until f starts executing.
Frankly, I would consider this another disadvantage of late-bound
arguments as defined under your proposal. I do not want argument
defaults to be able to have the side effect of creating additional local
variables in the function. (There is also the question of whether they
could assign in this manner to names already used by other arguments, so
that one argument's default could potentially override the default of
another.)
Unless it's otherwise denied, all valid forms of expression should be
valid in an argument default. They are already valid in early-bound
defaults:
def f():
... def g(a=(b:=42)): ...
... return locals()
...
f()
{'b': 42, 'g': <function f.<locals>.g at 0x7f9a7083ef00>}
That's true. I guess what I really mean is "I still think the walrus
was a bad idea". :-)
--
Brendan Barnwell
"Do not follow where the path may lead. Go, instead, where there is no
path, and leave a trail."
--author unknown
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