ROADMAP: Consistent missing value handling with new NA scalar (original) (raw)

I cleaned up my initial write up on the consistent missing values proposal (#27825 (comment)), and incorporated the items brought up in the last video chat. So I think it is ready for some more detailed discussion.

The last version of the full proposal can be found here: https://hackmd.io/@jorisvandenbossche/Sk0wMeAmB

TL;DR:

• I propose to introduce a new scalar (singleton) pd.NA that can be used as the missing value indicator (when accessing a single value, not necessarily how it is stored under the hood).
• This can be used instead of np.nan or pd.NaT in new data types (eg nullable integers, potential string dtype)
• Long term, we can see if there is a migration possible to use this consistently for all data types.

cc @pandas-dev/pandas-core