This document discusses the SOLID principles of object-oriented design. It introduces each of the SOLID principles - Single Responsibility Principle, Open/Closed Principle, Liskov Substitution Principle, Interface Segregation Principle, and Dependency Inversion Principle. It provides examples of how to apply these principles when designing classes and systems using object-oriented programming in Python. Resources for further reading about SOLID and examples of implementing it in code are also included.

1. S.O.L.I.D. Python

2. Alea Soluciones
Bifer Team

3. @eferro
@pasku1
@apa42
@nestorsalceda

4. Usual OO Systems
Rigid
Fragile
Immobile
Viscous

6. Why S.O.L.I.D. principles?
To create easy to maintain OO systems
Improve reusability
Easy testing

7. For creating
Clean Code

8. It's all about money

10. S.O.L.I.D
SRP - Single responsibility principle
DIP - Dependency inversion principle
OCP - Open/closed principle
LSP - Liskov substitution principle
ISP - Interface segregation principle

11. Principles
Not Rules

13. Car wash service
car wash job
when the car enters in the car wash
✓ it registers a job
customer notification
when service completed
✓ it notifies the customer
reporting
when client report requested
✓ it shows all wash services for that customer
3 examples ran in 0.0178 seconds

18. …
Some refactors / versions later

21. Depend upon Abstractions. Do not depend upon concretion

22. Compilation / Startup time
dependency
from <package> import module

23. Runtime dependency
self.collaborator.message()

25. Global State Problem
Implicit dependency problem
Concrete API

26. No dependency injection
Implicit dependency problem
Concrete API

33. Duck Typing Approved!!!

35. Liskov Substitution
principle violation

36. Python don't force type inheritance
For API implementation
(So, for reuse code, prefer Composition)

37. Derived types must be completely substitutable for their
base types

39. It isn't so important

40. A narrow interface is a better interface

41. SOLID Motivational Posters, by Derick Bailey
http://lostechies.com/derickbailey/2009/02/11/solid-development-principles-in-motivational-pictures/

42. car_wash code example
https://github.com/aleasoluciones/car_wash
SOLID definition (at wikipedia)
http://en.wikipedia.org/wiki/SOLID_(object-oriented_design)
Getting a SOLID start (Uncle Bob)
http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
Video SOLID Object Oriented Design (Sandi Metz)
http://www.confreaks.com/videos/240-goruco2009-solid-object-oriented-design

45. Thanks !!!
@eferro
@pasku1
@apa42
@nestorsalceda