On 02/12/2021 14:47, Steven D'Aprano wrote:
On Thu, Dec 02, 2021 at 11:00:33PM +1100, Chris Angelico wrote:
I'm still unsure whether this is a cool feature or an utter abomination:
def f(x=...):
... try: print("You passed x as", x)
... except UnboundLocalError: print("You didn't pass x")
...
f.__defaults_extra__ = ("n/a",)
f(42)
You passed x as 42
f()
You didn't pass x
That is absolutely an abomination. If your implementation has the
side-effect that setting a regular early-bound default to Ellipsis makes
the parameter unable to retrieve the default, then the implementation is
fatally broken.
It absolutely is not a feature.
It's backward incompatible:
15:03:04 R:\>python
Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> def f(x=...):
... try: print("You passed x as", x)
... except UnboundLocalError: print("You didn't pass x")
...
>>> f()
You passed x as Ellipsis
So I must agree with Steven that this should not be a feature.
Best wishes
Rob Cliffe
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