GitHub Actions: Faster Python runs with cached virtual environments (via) Adam Johnson shares his improved pattern for caching Python environments in GitHub Actions.
I've been using the pattern where you add cache: pip to the actions/setup-python block, but it has two disadvantages: if the tests fail the cache won't be saved at the end, and it still spends time installing the packages despite not needing to download them fresh since the wheels are in the cache.
Adam's pattern works differently: he caches the entire .venv/ folder between runs, avoiding the overhead of installing all of those packages. He also wraps the block that installs the packages between explicit actions/cache/restore and actions/cache/save steps to avoid the case where failed tests skip the cache persistence.
Recent articles
- Design Patterns for Securing LLM Agents against Prompt Injections - 13th June 2025
- Comma v0.1 1T and 2T - 7B LLMs trained on openly licensed text - 7th June 2025
- The last six months in LLMs, illustrated by pelicans on bicycles - 6th June 2025