The document discusses rewriting scripts originally written in Python into Kotlin. It compares features between the languages for tasks like parsing file formats, directories browsing, and bootstrapping. While Python is easier to get started, Kotlin offers benefits like enum classes, pattern matching, and extension functions. Rewriting in Kotlin produced a cleaner, more maintainable implementation.

1. 1From Python to Kotlin @Horgix / #TalkingKT
5 March 2020
From Python to Kotlin
Feedback from some scripts re-writing
Alexis “Horgix” Chotard

2. 2From Python to Kotlin @Horgix / #TalkingKT
Alexis “Horgix” Chotard
SRE & Coach DevOps
▼ 30% Development
▼ 40% Operations
▼ 30% Training, coaching, …
▼ Usually prototypes in Python
▼ First time Kotlin user in Oct. 2019
▼ Loves Rust
@Horgix
Horgix

3. 3From Python to Kotlin @Horgix / #TalkingKT
Warning!
This is a personal feedback from a personal experience
Lot of bias from my own knowledge :)

4. 4From Python to Kotlin @Horgix / #TalkingKT
Context & Usage
Talks/Speakers handling from GitHub files

5. 5From Python to Kotlin @Horgix / #TalkingKT
Sample - Talks list

6. 6From Python to Kotlin @Horgix / #TalkingKT
Sample - Talk file template

7. 7From Python to Kotlin @Horgix / #TalkingKT
What do we want to do?
▼ Files “parsing” - YAML frontmatter + Markdown body
▼ “Error” detection : missing infos, non-coherent infos, etc.
▼ Some stats would be nice
▼ Will be run mainly manually or from a CI pipeline

8. 8From Python to Kotlin @Horgix / #TalkingKT
First Python implementation
“Hey, let’s code something quick to make our life easier”

9. 9From Python to Kotlin @Horgix / #TalkingKT
At first, a simple set of Python scripts

10. 10From Python to Kotlin @Horgix / #TalkingKT
Then some “tests”

11. 11From Python to Kotlin @Horgix / #TalkingKT
“Let’s wrap everything in a Makefile!”

12. 12From Python to Kotlin @Horgix / #TalkingKT
“Well, that look hacky as f***…”
And indeed. It is was

13. 13From Python to Kotlin @Horgix / #TalkingKT
Rewrite everything in Kotlin!
(for science)

14. 14From Python to Kotlin @Horgix / #TalkingKT
Why Kotlin?
▼ Lot of momentum
▼ Looked cool and I wanted to play with it :)
▼ A lot of data collections computing that can all be done in memory
▽ Functional approach made easy by Kotlin
▽ Kotlin standard library looked like it could make things easier

15. 15From Python to Kotlin @Horgix / #TalkingKT
Let’s compare some use cases
Mainly about language features, libraries and stuff

16. 16From Python to Kotlin @Horgix / #TalkingKT
1. Talks format handling
and base language constructs

17. 17From Python to Kotlin @Horgix / #TalkingKT
Talk formats - Storage & field format

18. 18From Python to Kotlin @Horgix / #TalkingKT
Talk formats - Storage & field format

19. 19From Python to Kotlin @Horgix / #TalkingKT
Talk formats - Storage & field format (raw)

20. 20From Python to Kotlin @Horgix / #TalkingKT
Some wise words

21. 21From Python to Kotlin @Horgix / #TalkingKT
Better than enums : Enum classes <3

22. 22From Python to Kotlin @Horgix / #TalkingKT
Yes, there are (more limited) enums in Python too...

23. 23From Python to Kotlin @Horgix / #TalkingKT
1bis. Talks format handling
What about getting our enum value from what we parse?

24. 24From Python to Kotlin @Horgix / #TalkingKT
How to get a Enum value from our initial String
Python:

25. 25From Python to Kotlin @Horgix / #TalkingKT
Pattern matching <3
Python:
Kotlin:

26. 26From Python to Kotlin @Horgix / #TalkingKT
Function extensions <3
Python:
Kotlin:

27. 27From Python to Kotlin @Horgix / #TalkingKT
2. File parsing
YAML frontmatter + Markdown body

28. 28From Python to Kotlin @Horgix / #TalkingKT
File parsing in Python :) https://github.com/eyeseast/python-frontmatter

29. 29From Python to Kotlin @Horgix / #TalkingKT
File parsing in Python :) https://github.com/eyeseast/python-frontmatter

30. 30From Python to Kotlin @Horgix / #TalkingKT
File parsing in Kotlin :( https://github.com/atlassian/commonmark-java/
+ commonmark-ext-yaml-front-matterc

31. 31From Python to Kotlin @Horgix / #TalkingKT
File parsing in Kotlin :( https://github.com/atlassian/commonmark-java/
+ commonmark-ext-yaml-front-matterc

32. 32From Python to Kotlin @Horgix / #TalkingKT
3. Directories browsing
YAML frontmatter + Markdown body

33. 33From Python to Kotlin @Horgix / #TalkingKT
Directories browsing in Python :(

34. 34From Python to Kotlin @Horgix / #TalkingKT
Directories browsing in Kotlin :)

35. 35From Python to Kotlin @Horgix / #TalkingKT
Bootstrapping & Running
Getting started on a minimal software/script
and running it manually or in a CI pipeline

36. 36From Python to Kotlin @Horgix / #TalkingKT
Bootstrap - From installed tooling to a working “project”
▼ Python :
▽ Virtualenv
▽ pip install + pip freeze > requirements.txt
▽ Profit
▼ Kotlin :
▽ Maven Gradle configuration
▽ Directory/files structure way more strict/predefined
▽ IntelliJ IDEA “New Project” to the rescue

37. 37From Python to Kotlin @Horgix / #TalkingKT
Running in a CI Pipeline
▼ Python: cache dependencies & just run
▼ Kotlin: need to rebuild just in case
▼ Docker to the rescue

38. 38From Python to Kotlin @Horgix / #TalkingKT
Kotlin script
.kts

39. 39From Python to Kotlin @Horgix / #TalkingKT
Kotlin script
▼ .kts files
▼ Top level instructions
▼ kotlinc -script <file>.kts
▼ Can be used for your Gradle files :)
▼ Does not support multiple files :(
https://kotlinlang.org/docs/tutorials/command-line.html#using-the-command-line-to-run-scripts

40. 40From Python to Kotlin @Horgix / #TalkingKT
kscript
https://github.com/holgerbrandl/kscript

41. 41From Python to Kotlin @Horgix / #TalkingKT
kscript - Imports, libraries and entrypoint definition

42. 42From Python to Kotlin @Horgix / #TalkingKT
kscript surprise n°1 - Imports clash

43. 43From Python to Kotlin @Horgix / #TalkingKT
kscript surprise n°2 - Bad handling of typealias

44. 44From Python to Kotlin @Horgix / #TalkingKT
kscript works fine in the end :)
Demo

45. 45From Python to Kotlin @Horgix / #TalkingKT
Take away
What did I take away from this switch from Python to Kotlin

46. 46From Python to Kotlin @Horgix / #TalkingKT
Take away
▼ Easier / More lightweight to start with Python than Kotlin
▼ More complex to run Kotlin scripts than Python, but kscript saves the day
▼ Thanks Kotlin interoperability with Java
▼ Community libraries are tailored to the language usual use cases
▼ List comprehension vs functional chaining
▼ ❤ Enum Classes
▼ ❤ Pattern matching
▼ ❤ Extension functions

47. 47From Python to Kotlin @Horgix / #TalkingKT
Take away - Self-Q&A
▼ Did I get to re-implement all the things in Kotlin?
▽ Nope, didn’t implement README generation because parsing files was
already too much of a pain, so generating them…
▼ What are the key differences between both implementations in the end?
▽ Kotlin version looks way more clean and maintainable to me
▼ If I were to do it again, would I do it in Python or Kotlin?
▽ Same, first Python then Kotlin :)

48. 48From Python to Kotlin @Horgix / #TalkingKT
5 March 2020
From Python to Kotlin
Feedback from some scripts re-writing
Alexis “Horgix” Chotard
Q&A