The core principle asserts that software robustness and clarity are achieved by separating raw external data from strict domain logic through explicit state modeling and constraint enforcement. In the specific subject area of object-oriented programming, particularly within Python, `None` is formally defined not merely as a value but as an error condition indicating broken assumptions; therefore, its usage must be minimized via default values (e.g., empty lists), exception handling for invalid states, protocol-based null objects, and sentinel variables to represent missing inputs. This concept relates directly to the broader discipline of defensive programming by enforcing strict invariants at the core domain level while acknowledging that `None` belongs exclusively at system boundaries where data integrity cannot be guaranteed.
The core principle asserts that software robustness and clarity are achieved by separating raw external data from strict domain logic through explicit state modeling and constraint enforcement. In th…