On Sat, Oct 31, 2020 at 09:05:43PM -0700, Guido van Rossum wrote:
> Hm, for PEP 622/634 we looked at this and ended up making it so that this
> is the default -- you only have to write
> ```
> {'spam': spam, 'eggs': eggs} = mapping
> ```
> and any extra keys are ignored. This is because for the common use case
> here we want to ignore extra keys, not insist there aren't any.
Regardless of which is commoner than the other, what about the use-case
where you do want to insist that the mapping is an exact match? Having
matched the two keys how do I say that there are no more keys?
In the case of the `match` statement, I think that "ignore extra keys"
by default is risky. Consider something like this:
match mapping:
case {'spam': spam}:
print(spam)
case {'spam': spam, 'eggs': eggs}:
print('this will never be called')
There's no case that will match the second that isn't already captured
by the first.
--
Steve
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