Edit: I created a small demo in Github, if you're interested.

Package managers

• no package manager is a (very) bad idea
• requirements.txt is a good improvement, but makes it harder to do some things, eg lock sub-dependencies versions and specify development-only dependencies
• pipenv is good, but I prefer poetry

Python manager

• pyenv makes it easy to install and manage multiple python versions

Code formatters

• black: formats the code ("any color you want, as long as it's black")
• isort: sorts the imports ("i sort so you don't have to")
• darker: formats code only since last commit (gradual formatting for older projects)

Code linters

• pylint: decent start but too many false positives
• pycodestyle: popular, didn't use it much
• flake8: popular and used it a bit, it's ok
• ruff: the cool kid in the block: much faster and supports rules from different linters

Honorable mentions: bandit, bugbear, pyupgrade

Test runners

• unittest: native, it's decent but verbose
• pytest: widely used, supports plugins
• locust: didn't use it much but potentially useful for load testing
• hypothesis: property based testing

Centralized configuration

Centralize your configs in pyproject.toml such that every application runs the tools consistently:
- CLI
- IDE
- git hooks / pre-commit
- CI/CD

flake8 didn't support pyproject.toml because it wasn't standard - well now it is, in PEP 621, but it doesn't support it anyway. Bad flake8!