[Python-Dev] Re: PEP 622: Structural Pattern Matching

2020年6月24日 04:02:45 -0700

On 24/06/20 11:57 am, Guido van Rossum wrote:
Matched key-value pairs must already be present in the mapping, and not created
on-the-fly by ``__missing__`` or ``__getitem__``. For example,
``collections.defaultdict`` instances will only match patterns with keys that
were already present when the ``match`` block was entered.
Does that mean the pattern matching logic is in cahoots with
collections.defaultdict? What if you want to match against
your own defaultdict-like type?
--
Greg
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