Migrating from Java to Python

1. From Java to Python
python.be meetup #5
by Ivo Houbrechts

2. Hi, I'm Ivo
FreelanceSoftwareCraftsman
ProfessionalDeveloperSince1997
UpcycledCode

3. Agenda
Whatwedevelop
Loveatfirstsight
Therockyroad
PyprojectX:thedealmaker

4. What we develop
Applications/RESTAPIs
~70gitrepositoriescheckedout
Java(Groovy),NodeJs,Python(Combined)
oldestrepo:2012
15+Pythonprojects

5. Love at first sight

6. Python 💕
NoCeremonialCode
Indentationbased
Comprehensions
Decorators
Batteriesincluded
Standardlibrarypackedwithusefulstuff
Pip/PyPI
Plentyoflearningresources

7. Python for AWS Lambda
IncomparisonwithJavaandJavaScript:
Betterlibrarysupport
Boto3
LambdaPowertools
Contractfirstdevelopment
OpenAPI/Swagger
Connexion+Flask+ServerlessWSGI

8. A unique chance to
compare
Distributedtracingimplementation
ImplementedinJava,JavaScriptandPython
Samefunctionality
SlightlymorefeaturesinPython

9. The verdict from SonarQube
Python JavaScript Java
LoC 223 249 754
Cyclomatic
Complexity 42 48 92
CognitiveComplexity 27 30 37

10. The rocky road

12. The preparation

14. Search Libraries
AWSspecific
Boto3
LambdaPowertools
PynamoDB
General
Connexion
Flask
ServerlessWSGI

15. Migrate custom AWS library
SmallJavaScriptlibrary
Helpersforeventhandling
APIGateway
S3
SQS
Utilityfunctions

16. Team Onboarding

17. Python Installation
AnticipatesupportofmultiplePythonversions
3differentJavaversions
2differentNodeJsversions
pyenv
theWindowsguyjustsurvived
frustrationsonMaccausedbydifferent
installationoptions
Onetimeeffort🙄
Auto-selectpythonwith.python-version😃

18. Dependency Management
Poetry
Worksasadvertised
Butnotforeveryone😵‍💫
Dependingontheinstallationmethod,yougotadifferent
version🤨

19. Tool dependency hell
BesidesPoetry,weuseblack,isort,pre-commit,...
10projectsx5toolsx3versions=upto150
combinations😱
ShowStopper!🛑

20. How do others solve this?
installtoolsasdevdependencies
impactonruntimedependencies
downgradeofdependenciesatbest
versionconflictsatworst
f.e.AWSSAMnotcompatiblewithboto3
docker
notdeveloperfriendly
doesnotplaywellwithIDEs

21. PyprojectX: the deal maker

22. What we learned from
Gradle
OnlydependsontheJavaruntime
Don'trelyonlocallyinstalledtools;tools
changeovertime!
Useawrapperscript
Downloadthecorrectversionifnotpresent
Don'tpolluteyourlocalenvironment
Storemostintheprojectdirectory

23. PyprojectX
Wrapperscripts
pwfor*nixandpw.batforWindows
Configurationinpyproject.toml
(Versioned)Tools
Frequentlyusedcommands

24. PyprojectX example
[tool.pyprojectx]
pdm = { requirements = ["pdm==2.9.3"],
post-install = "pw@setup-pre-commit" }
ruff = "ruff==0.0.287"
pre-commit = "pre-commit==3.4.0"
jupyter = ["jupyterlab", "-e ."]
[tool.pyprojectx.aliases]
install = "pdm install"
run = "pdm run"
test = "run pytest tests/unit"
start = "run python -m tests.local_flask"
outdated = "pdm update --outdated"

25. PyprojectX Demo
$ ./pw --info
$ ./pw install
$ ./pw i
$ ./pw start
$ cd tests/unit
$ ../../pw run pytest
$ ./pw pdm add requests
$ px run pytest

26. But still...

27. 'pip install pdm==2.5.3' !=
'pip install pdm==2.5.3'
Releasesofdownstreamdependenciescanbreaka
Pythontool🤯
...anddockerwon't(always)solvethisforyou😭
SeePDMissue1883

28. PyprojectX v2
locktoolversions
simplifiedconfiguration
bugfixesandfeaturerequests
expectedrelease:january2024

29. Conclusions
Pythonisagreatlanguage
Dependencymanagementneedsextraattention
PyprojectXhelpsalothere
MigratingfromJavaorNodeJsisworthwhile
AtleastforAWSLambda

30. Questions?