denial 0.0.2

Is one None not enough for you? There's more

denial

There is a small but annoying misunderstanding in the design of Python as a language. The language defines the constant None, which designates a special object that is used as a "stub" when it is not possible to use the "real" value. But sometimes, when implementing libraries, it is not possible to distinguish None, passed by the user as the default value, from None, which means that the value is really undefined. In some rare cases, this distinction is important.

For example, the dataclasses library defines a special MISSING constant for such cases. This is used to separate the cases when the user has not set a default value from the case when he has set None as the default value. However, the use of MISSING is tied to the use of this library, and sometimes this constant may be needed for completely different purposes.

This library defines just such an object: None for situations where you need to distinguish None as a value from the user, and None as a designation that something is really undefined. This value should not fall "outside", into the user's space, it should remain only inside the libraries implementations.

Well, how to use it?

Let's start with the installation:

pip install denial

This is how this additional version of None and its class are imported (can be used for type hints or checks via isinstance):

from denial import InnerNone, InnerNoneType

InnerNone is used the same way as None, with a couple of additional caveats:

1. InnerNone is not an instance of NoneType, it has its own parent class.

2. InnerNone cannot be used as your own type hint. What am I talking about? Let's look at the documentation:

When used in a type hint, the expression None is considered equivalent to type(None).

Official typing documentation

In most type checkers, this is implemented using a special "crutch", an exception in the code that cannot be repeated for any other value. Therefore, use InnerNoneType as a type hint.