ABCClasses for DatetimeArray etc?

[jbrockmendel]

There are a handful of places in the code where we check for for isinstance(other, ABCDatetimeIndex) or getattr(other, '_typ', None) == "datetimeindex" (and analogous places for TDI, PI). In most of these cases DatetimeArray/TimedeltaArray/PeriodArray should be handled symmetrically. Thoughts on what _typs to give them?

[jreback]

we don’t have this notion for EA but we either should or alternatively just use isinstancs o the EA (iow don’t define ABCs

but if it makes it simpler i would make an ABC hierarchy that is distinct from the current ones

[jbrockmendel]

Well there is an ABCExtensionArray. For some of it we can probably get away with changing e.g isinstance(foo, ABCPeriodIndex) to is_period_dtype(foo). The cython cases that explicitly check _typ will need special handling.

[jbrockmendel]

Closed by #23502