"Persistent / Immutable / Functional data structures for Python"
https://github.com/tobgu/pyrsistent

IIRC, there are a number of threads discussing adding const as a language feature? It may be worth linking those here / in the gh issue? IIUC, the linked proposal describes adding const as an annotation feature for static analysis only.

Would const as a language feature have any effect on the gilectomy? e.g. less locks required

Ways to achieve practical runtime const (~immutability):
* add a has_key() check in __setattr__ https://gist.github.com/ashwin/e3844158e3d7afd16adb
* define an @property without a propname.setter (for a __dunder_prefixed class attr which will otherwise be name-mangled)
* const as a language feature

.

* from typing import Const
   this would be a great hint for static analysis, but would things really be const?