The empty tuple syntax in type annotations, `Tuple[()]`, is not obvious from the examples given in the documentation (I naively expected `Tuple[]` to work); it has been documented in PEP 484[1] and in mypy[2], but not in the documentation for the typing module.

[1]: https://www.python.org/dev/peps/pep-0484/#the-typing-module
[2]: https://github.com/python/mypy/pull/4313

That’s correct. Mind making a PR?

What is better, Tuple[()] or Literal[()]?

PEP 586 doesn't currently allow Literal to contain tuples, so Tuple[()] is the only option.

> What is better, Tuple[()] or Literal[()]?

In this context, Tuple[()] is better, as the discussion is about how to write the type of various tuples. Tuple[()] is just the edge case of the type of the empty tuple.

Josh, please sign the CLA and adjust the wording per my request in the PR.

New changeset 8a784af750fa82c8355903309e5089eb2b60c16b by Miss Islington (bot) (Josh Holland) in branch 'master':
bpo-37814: Document the empty tuple type annotation syntax (GH-15208)
https://github.com/python/cpython/commit/8a784af750fa82c8355903309e5089eb2b60c16b

New changeset 6ad902a08814909b4d52c4000d5a10ce58516dac by Miss Islington (bot) in branch '3.8':
bpo-37814: Document the empty tuple type annotation syntax (GH-15208)
https://github.com/python/cpython/commit/6ad902a08814909b4d52c4000d5a10ce58516dac

Thanks Josh! The automated backport to 3.7 didn't work, that's okay, so I'll close this now. (Though if you want to experiment with the cherry-picker tool go ahead.)

New changeset 37fd9f73e2fa439554977cfba427bf94c1fedb6b by Miss Islington (bot) (Josh Holland) in branch '3.7':
[3.7] bpo-37814: Document the empty tuple type annotation syntax (GH-15208) (GH-15262)
https://github.com/python/cpython/commit/37fd9f73e2fa439554977cfba427bf94c1fedb6b