On Thu, Dec 02, 2021 at 11:00:33PM +1100, Chris Angelico wrote:
On Thu, Dec 2, 2021 at 8:40 PM Steven D'Aprano email@example.com wrote:
Depending on the implementation, you *might* be able to inspect the function and see the default expression as some sort of callable function, or evaluatable code object. (That would be nice.)
Unfortunately not, since the default expression could refer to other parameters, or closure variables, or anything else from the context of the called function. So you won't be able to externally evaluate it.
Why not? Functions can do all those things: refer to other variables, or closures, or anything else. You can call functions. Are you sure that this limitation of the default expression is not just a limitation of your implementation?
I'm still unsure whether this is a cool feature or an utter abomination:
... 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
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.