core_lesson9

Lesson 9 - No Object is an Island

Ch2 Object Interactions

• Dependency when an object method requires another object
• Aggregation or Composition
  • When an object is part of another
  • Initialising
    • Aggregation
      • Passing an instance to a constructor
      • Less exclusive
    • Composition
      • Create the object inside the constructor
      • Completely exclusive
• Association
  • "has a" relationship, not ownership

Ch5 Comprehensions

• Set comprehension
  • {val for val in s}
• Dict comprehension
  • {k: v for (k, v) in d.items()}
• Generator expressions
  • If values aren't needed to be pre-stored
  • gen = (n ** 2 for n in range(10)
  • next(gen), ...
  • Generators are iterable

Ch6 JSON

• json.load loads file object into data object
• json.loads loads json string into data object
  • Deserialisation
• json.dump loads data object into string, then writes into file object
  • Serialisation

Ch8 Python Packages

• Namespace packages
  • Allows files to be spread across directories
  • Import by
    • sys.path.append(loc)
• Regular packages
  • Must include a __init__.py after python3.3
    • Usually empty or some magic variable initialisation code
    • __version__ version data
    • __author__ author name
    • __all__ allow import * and define what is included
  • Mutually exclusive with namespace packages

Ch9 Exception Instances

• Index arguments in an error by args = error.args