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).
flufl.enum has been in use for Mailman for many years, and I would like to hear
Barry's opinion on this.
--
Steven
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