26.04.13 11:00, Greg Ewing написав(ла):
However, there's a worse problem with defining enum
inheritance that way. The subtype relation for extensible
enums works the opposite way to that of classes.
To see this, imagine a function expecting something
of type Colors. It knows what to do with red, green and
blue, but not anything else. So you *can't* pass it
something of type MoreColors, because not all values
of type MoreColors are of type Colors.
On the other hand, you *can* pass a value of type Colors
to something expecting MoreColors, because every value of
Colors is also in MoreColors.
I propose do not use an inheritance for extending enums, but use an import.
class Colors(Enum):
red = 1
green = 2
blue = 3
class MoreColors(Enum):
from Colors import *
cyan = 4
magenta = 5
yellow = 6
An inheritance we can use to limit a type of values.
class Colors(int, Enum): # only int values
red = 1
green = 2
blue = 3
Colors.viridity = green
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