Comment by throwaway2037

Here is the sample code from the article:

    > MISSING = sentinel("MISSING")

    > def update_email(user_id: int, email: str | None | MISSING = MISSING) -> None:
    >     if email is MISSING:
    >         return  # nothing to update
    >     elif email is None:
    >         db.delete_email(user_id)
    >     else:
    >         db.set_email(user_id, email.lower())  # narrowed to str

I see this style frequently from long time Python programmers. The language is so dynamic that people begin to think this is a good way to program. Hot take: It is not. Why not two different functions called delete_email() and set_email()? That would be more clear.