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[Python-Dev] PEP 218 update questions
A.M. Kuchlingamk@nyman.amk.ca
Sun, 13 Oct 2002 17:38:38 -0400
I've just updated PEP 218 to match the sets.py module that's in CVS. The original PEP text had a single Set class, and Set instances frozeafter their __hash__ was called so you could use a set as a dictionarykey. sets.py takes a more straightforward approach, with distinct Setand ImmutableSet classes.Two things in the PEP need to be updated to take this change into account.1)The long-term proposal in PEP 218 lists a single built-in conversionfunction, set(iterable). This made sense when there was a single Setclass, but now this needs to be updated. How would instances of a built-in immutable set type be created?Would there be a second immutable_set() built-in, or would the set()function take an additional argument: set(iterable, immutable=True)?2)The PEP proposes {1,2,3} as the set notation and {-} for the emptyset. Would there be different syntax for an immutable and a mutableset? My thought is, "no"; {1,2,3} or {-} is always mutable, and animmutable set would be written as immutable_set({1,2,3}). That's upto python-dev, though, but whatever gets chosen needs to be specifiedin the PEP.--amk
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