Dev Blog

Summary ​

Conclusions ​

Inheritance defines a relationship between types and can reuse an implementation. Polymorphism lets a client work with a shared role. ABC makes some requirements explicit at instantiation, while Protocol describes a structural contract for an analyzer. MRO defines lookup order, and composition allows independent replacement of parts of behavior. Design is verified through substitution and contract tests, not merely a correctly drawn arrow.

Self-check questions ​

  1. How do you declare a derived class and call base initialization?
  2. What does super mean in multiple inheritance?
  3. How does isinstance differ from an exact type check?
  4. What problem does a polymorphic loop solve?
  5. Why is a matching method name insufficient for a contract?
  6. When does ABC prevent creating an instance?
  7. How do you declare an abstract property?
  8. What is a template method?
  9. How does nominal typing differ from structural typing?
  10. What does runtime_checkable not check?
  11. What does register change, and what stays unchanged?
  12. What guarantees do override and final provide at runtime?
  13. How does C3 order a diamond hierarchy?
  14. What contract should a mixin have?
  15. When can a square not substitute for a mutable rectangle?
  1. ABC: https://docs.python.org/3.14/library/abc.html.
  2. Protocols: https://peps.python.org/pep-0544/.
  3. Collections: https://docs.python.org/3.14/library/collections.abc.html.
  4. MRO: https://docs.python.org/3.14/howto/mro.html.