On 29/04/2013 21:00, Steven D'Aprano wrote:
On 30/04/13 05:02, MRAB wrote:
Why is that backwards? MoreColor is a subclass of Color, so
instances of MoreColor are instances of Color, but instances of
Color are not instances of MoreColor. That's normal behaviour for
subclasses. (All cats are mammals, but not all mammals are
cats.)
Let's say that Color is red, green, or blue.
Let's also say that MoreColor is superset of Color, in other words,
any of Color, plus cyan, magenta, or yellow.
Red is a Color and a MoreColor (member of Color and MoreColor).
Yellow is a MoreColor, but not a Color (member of MoreColor but
not Color).
That's the opposite of the rules of inheritance.
Membership != inheritance, you are conflating two independent
concepts. I would expect that for membership testing, you should say
"value in MoreColor", not isinstance(value, MoreColor).
I do know the difference, but it's not helpful that you're creating the
enum with a "class" statement!
flufl.enum has been in use for Mailman for many years, and I would
like to hear Barry's opinion on this.
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