PEP 683: Immortal Objects, Using a Fixed Refcount
Under this proposal, any object may be marked as immortal.
“Immortal” means the object will never be cleaned up (at least until
runtime finalization). Specifically, the refcount for an immortal
object is set to a sentinel value, and that refcount is never changed
by Py_INCREF(), Py_DECREF(), or Py_SET_REFCNT().
For immortal containers, the PyGC_Head is never
changed by the garbage collector. ⌘ Read more