[Python-ideas] Add new `Symbol` type

[Ed Kellett]

Hi!

On 2018-07-05 20:38, Flavio Curella wrote:
> More than once I've found myself wanting to create a 'sentinel' value. The
> most common use case is to differentiate between an argument that has not
> been provided, and an argument provided with the value `None`.

I generally do something like

    _nothing = object()

> Furthermore, without a common implementation in the std library, various
> Python libraries had to write their own implementations, which all differs
> in functionality and behavior.

What functionality does such a thing actually need?