On Sat, Dec 24, 2022 at 11:34:19AM -0500, Shironeko wrote:
>
> Is the => syntax needed? as far as I can think of, the only time where
> late evaluation is needed is when the expression references the other
> arguments.
You are missing the most common case, the motivating case, for
late-bound defaults: mutable defaults.
def spam(x, y=>[]):
pass
Here the intention is to have y's default be a *different* list each
time you call spam(x), instead of the same list each time.
The ability for default values to refer to other parameters is a Nice To
Have, not a Must Have. It has been a very long time since I have read
the PEP, and I don't remember whether it reviews other languages to see
what functionality they provide for defaults, but I don't think many
other languages allow you to set the default of one parameter to be
another parameter.
--
Steve
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