People working with sum types might expect the instances of the nested class to be instances of the enclosing class. So if the nested class is a namedtuple, you get a sum type. The only problem is that there's no way to express this subtype relationship in code.
Elazar בתאריך יום ד׳, 27 ביוני 2018, 11:59, מאת Guido van Rossum <gu...@python.org >: > Sounds to me really strange that the nested class would become a member. > Probably because everything becomes a member unless it's a function (maybe > decorated)? > > On Wed, Jun 27, 2018 at 7:47 AM Ethan Furman <et...@stoneleaf.us> wrote: > >> Consider the following Enum definition: >> >> class Color(Enum): >> RED = 1 >> GREEN = 2 >> BLUE = 3 >> @property >> def lower(self): >> return self.name.lower() >> def spam(self): >> return "I like %s eggs and spam!" % self.lower >> class SomeClass: >> pass >> >> Which of the above Color attributes are enums, and which aren't? >> >> >> . >> >> >> . >> >> >> . >> >> Answer: >> >> - RED, GREEN, and BLUE are members >> >> - lower and spam() are not >> >> - SomeClass /is/ a member (but not its instances) >> >> >> Question: >> >> Should `SomeClass` be an enum member? When would it be useful to have >> an embedded class in an Enum be an enum member? >> >> >> The only example I have seen so far of nested classes in an Enum is when >> folks want to make an Enum of Enums, and the >> nested Enum should not itself be an enum member. Since the >> counter-example already works I haven't seen any requests >> for it. ;) >> >> So I'm asking the community: What real-world examples can you offer for >> either behavior? Cases where nested classes >> should be enum members, and cases where nested classes should not be >> members. >> >> Thanks! >> >> -- >> ~Ethan~ >> _______________________________________________ >> Python-ideas mailing list >> Python-ideas@python.org >> https://mail.python.org/mailman/listinfo/python-ideas >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > > > -- > --Guido van Rossum (python.org/~guido) > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ >
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