adv_lesson2

Lesson 2 - Advanced Object-Oriented Programming

Ch2 Polymorphism

• Pillars of OOP - APIE
  • Abstraction
  • Polymorphism
  • Inheritance
  • Encapsulation
• Ability to take many forms
• Abstract class
  • Have at least one abstract method
  • NotImplementedError raised when invoking an abstract method
  • @abstractmethod decorator declare abstract method
• Duck typing
  • Classify objects by their behaviour
    • Does it have a method
  • Iterables only need the __iter__() method
    • Which only requires __next__()
  • Scikit-learn
    • Estimators must have fit()
    • Predictor must have predict()
    • Transformer must have transform()
    • Model must have score()
• Interfaces
  • Not required, python is dynamically typed

Ch3 Encapsulation

• Add __var_name double underscore before var to make private
  • Use getters and setters methods
• @property decorators
  • Allows reading of properties with syntax obj.prop
• @prop.setter decorator
  • Allows assigning of properties with syntax obj.prop
• Private vars are not accessible to sub-classes
  • Use one underscore instead
• Not strictly enforced

Ch4 Class Attributes and Methods

• Defined outside the constructor
  • Accessed by Class.prop_name
• Define constants with all CAPS
• @classmethod decorator
  • Defines a class method
  • Equivalent to c++ static methods
  • Used as constructor
    • create(cls, attr) return cls(attr)
• @staticmethod decorator
  • Just a normal function defined in the class
  • Not necessarily

Ch5 Advance Python Features

• Type hinting
  • Allows annotated functions
• Named tuples
  • from collections import namedtuple
  • Initialisation by namedtuple("Name", "attr1, attr2")
  • Allows access by tup.attr1
• Data class
  • @dataclass class decorator
  • Saves __init__() and __repr__() code