Course Note of *Python: Design Patterns*

note

The course is on Coursera

understanding design patterns

  • what?
    • well-known solutions for recurring problems
  • why?
    • don’t reinvent wheels
    • reuse best practices
  • characteristics
    • language neutral
    • dynamic
    • incomplete by design to promote customization
  • types
    • creational
    • structual
    • behavioral
  • OOP (object-oriented programming)
    • design pattern relies on OOP
    • attributes + methods
    • inheritence & polymorphism
  • pattern context
    • participants and their rols
    • quality attributes: nonfunctional requirements
    • forces: various factors or trade-offs to consider
    • consequences: side effects by decision makers
  • pattern language
    • name
    • context
    • problem
    • solution
    • related patterns

creational patterns

factory

  • create and return object on the fly
    • flexibility of adding new classes
  • problem
    • uncertainties in types of objects
    • runtime decision of types of objects

abstract facotry

  • a factory dynamically uses different factories to create objects on the fly
  • problem
    • create a family of related objects at runtime
  • concepts
    • abstract factory
    • concrete factory (the real factory used at runtime)

singleton

  • only one object from a class
  • problem
    • cache information shared by multiple objects