PEP 661 -- Sentinel Values

• reader

  30 416 9.2 Python

  A Python feed reader library. (by lemon24)

The exact same problems None has when it's not a valid value. None is different from the variable type, that's why you have Optional[VarType], which is an alias for Union[VarType, None]; you can model this in exactly the same way: Union[VarType, MissingType]; here's an example.

• Werkzeug

  11 6,539 8.5 Python

  The comprehensive WSGI web application library.

  

Werkzeug (library used by Flask) had a repr for its sentinel long before getting type annotations.

• WorkOS

  workos.com sponsored

  The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.

  

• attrs

  11 5,074 9.1 Python

  Python Classes Without Boilerplate

  

attrs has at least two.

• peps

  36 4,133 9.8 reStructuredText

  Python Enhancement Proposals

  

A lot of PEPs get abandoned/rejected, or postponed (and this is fine, that's how the process is supposed to work).

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