[Python-Dev] constant/enum type in stdlib

[Barry Warsaw]

On Nov 23, 2010, at 05:02 PM, Michael Foord wrote:

>> * Enums are not subclassed from ints or strs.  They are a distinct data type
>>    that can be converted to and from ints and strs.  EIBTI.
>
>But if we are to use it *in* the standard library (as opposed to merely
>adding a module *to* the standard library) there are backwards compatibility
>concerns. Where modules are already using integers for constants then
>integers still need to work.

Is int(enum_value) enough, or must the enum value actually *be* an int?

>One easy way to achieve this is to subclass integer. If we don't do that
>(assuming we decide that putting a solution in the standard library is
>appropriate) then we'll have to evaluate what we mean by backwards
>compatible. If the modules that use the constants aren't to change then
>comparing equal to the underlying value is the minimum (so that the original
>value can still be used in place of the new named constant). Not sure if
>you'd be happy to make that change in flufl.enum.

I'm not sure either.  In flufl.enum enum_class(i) also works as expected.

>> * The typical way to create them is through a simple, but explicit class
>>    definition.  I personally like being explicit about the item values, and
>>    the assignments are required to make the metaclass work properly, but
>>    Michael's convenience patch is totally appropriate for cases where you
>>    don't care, or you want a one-liner.
>
>If make_enum was to take a set of values to use (as Antoine suggested) I
>don't see what's un-explicit about it.

When I saw your patch I immediately thought that I could add a default
argument that was something like `int_iter`, i.e. an iterator of integers for
the values in the string.  I suspect YAGNI, which is why I didn't just add it,
but I'm not totally opposed to it.

-Barry
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