Understanding Metaclasses
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This document discusses metaclasses in Python. It begins with an introduction to objects, instances, and classes. It then asks what a metaclass is, and how metaclass attributes and methods affect a class differently than class attributes and methods. It also discusses the unique aspects of metaclasses, such as the __new__ and __init__ methods, and compares them to class decorators. Finally, it provides some examples of sane use cases for metaclasses, such as form libraries, ORMs, and declarative programming. The document ends with an invitation for questions.
Understanding Metaclasses
- 2. • Computer science student at TU Berlin • Software Developer at Charité - Universitätsmedizin Berlin • Involved in Flask, Werkzeug, Babel and many other open source projects
- 3. What is an object?
- 4. What is an instance?
- 5. What is a class?
- 6. What is a metaclass?
- 7. How does an instance attribute of a classes metaclass affect that class?
- 8. How is this different from a class attribute?
- 9. How does a method of a classes metaclass affect that class?
- 10. How is this different from a class method defined with @classmethod?
- 11. Is there anything unique to metaclasses?
- 12. def __new__(cls, name, bases, namespace, **kwargs)! ! def __init__(self, name, bases, namespace, **kwargs)
- 13. How is this different from class decorators?
- 14. @classmethod def __prepare__(cls, name, bases, **kwargs)
- 15. def __call__(self, *args, **kwargs)
- 16. (Sane) use cases? • Form libraries • ORMs • Anything declarative
- 17. Q&A