> With tuple unpacking, using _ as a throwaway label is also OK.

I see this sometimes, but the problem is that this breaks internationalization using gettext, commonly imported under the name _:

   from gettext import gettext as _

(For those who’ve never seen it, “_” is then used as a function which wraps strings, like _("Book"); translation tools can then parse the source code, deduce that “Book” is a term which needs translating, and at runtime the “_” function can return the translated term instead of the original string when a different language is needed. The name “_” for this functionality predates Python and is a common feature across most programming language using the gettext method of internationalization. It is therefore unfortunate that some Python users have taken “_” to be a kind of throwaway variable.)