Presentation from "Code Reviews in Python" session at the Zurich Python User Group from June 2016

1. Code Reviews in Python
César Cárdenas Desales
Zürich Python User Group, June 2016

2. 2
About me
● Software Architect at Webrepublic AG
● Python user since v.2.0
● Co-organizer of the Swiss Python Summit

3. ¿What are Code Reviews?
3
Systematic examination of computer source code…
- Wikipedia

4. Benefits
4
● Timeless
● Spread knowledge
● The Ego Factor
● Increase quality of software

5. Timeless
5
● Being here for a while (Fagan, 1976)
● Not going away any time soon
● Technology agnostic
● Not a fad

6. Timeless
6
● Fad?
○ Machine learning?
○ SOA?
○ OOP?
○ Client server architecture?
○ Big data?
○ Cloud computing?
○ SVN
● Fad
○ Aspect Oriented Programming
○ Java applets
○ Visual Programming
○ Enterprise JavaBeans
○ CGI (Web)
○ Webmasters

7. Spread knowledge
7
● Beginners learn from the experts’ code
● The experienced get to know other modules or
systems
● Increases “Bus Factor”

8. The Ego Factor
8
● No “quick and dirty” fixes
● Reputation at stake on each commit

9. Increase quality of software
9
● Reviewed solutions tend to be better
● Defects are found and fixed early
Source: IBM Systems Sciences Institute

10. Assign Reviewers
10
● Everyone participates
● Works well with couples
● ¿How long?
~1 sprint or week

11. Assign Reviewers
11
● 50%
● 100%

12. 12
Code Review with Github
Implementation
Pull
Request
Discusion
Preparation Revision Closure
Revision
Merge
Branch
12
Commit

13. Preparation
13
1. Branch
2. Commit
3. Pull Request

14. Revision
14
4. First response
5. Review code
6. Written comments /
discussion

15. Closure
15
6. Implement changes under agreement
7. Merge

16. 1616
Rule #1
It’s not personal

17. Basic Rules
17
● Respond (ACK) and solve in a timely manner
● Not too little, not too much
(400 loc. max.)
● Ask before overwriting somebody’s code
● Use checklists

18. Code conventions and style guides
Criteria - Pythonic code
18
Pycodestyle / Flake8 / Pylint

19. Code conventions and style guides
Criteria - Pythonic code
19
Pythonic code
pycodestyle / Flake8 / Pylint

20. Code conventions and style guides
Criteria - Pythonic code
20
Pythonic code
pycodestyle / Flake8 / Pylint

21. Criteria - Pythonic code
21
Zen of Python
>>> import this
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
...

22. Pythonic code
Criteria - Pythonic code
22

23. Pythonic code
Criteria - Pythonic code
23

24. Pythonic code
Criteria - Pythonic code
24

25. Pythonic code
Criteria - Pythonic code
25

26. TODO/FIXME: Name and shame, ticket number, date
Criteria
26
Cyclomatic complexity

27. Criteria
27
Input data validation
Updated comments & docstrings
Dead or commented out code

28. Criteria
28
exec() / eval()
Passwords or tokens in repository

29. Automated unit tests: unittest / pytest / nose / coverage
Criteria
29
Efficient algorithms
Edge cases / off by 1 errors
Duplicated code / copy & paste

30. Criteria
30
Antipatterns
● God class/function
● Lasagna code
● Magic numbers
● Reinventing the wheel (!)

31. Criteria
31
Antipatterns
● Circular dependencies
(relative imports)
● Premature optimization -> YAGNI
● Boat Anchor
● Object Orgy

32. Criteria
32
Is there a better solution?
Is it scalable?

33. 33
Let’s make it happen.
Thanks!
cesar.desales@webrepublic.com
@ccdesales