pip vs Poetry: Which Python Dependency Tool for CI?
In CI, the gap between pip and Poetry is really a gap between ad-hoc installs and a committed lockfile.
Both install Python dependencies, but Poetry adds a project model and a real lockfile, while pip stays minimal and ubiquitous.
| pip | Poetry | |
|---|---|---|
| Lockfile | None native (use pip-tools / requirements.txt) | poetry.lock (built in) |
| Reproducible installs | Only if you pin everything | Yes, from the lock |
| Dependency resolver | Basic (backtracking, improving) | Full resolver |
| CI install | pip install -r requirements.txt | poetry install --no-root |
| Caching key | Hash of requirements.txt | Hash of poetry.lock |
For CI specifically
Poetry gives you a deterministic build out of the box: commit poetry.lock and every run installs the same versions. Bare pip with an unpinned requirements.txt drifts over time and causes "works on my machine" CI failures. pip is still the lightest option and the right call for simple scripts or when a tool only documents pip.
Cache the right thing
Key your dependency cache on the lockfile (poetry.lock) or the pinned requirements.txt, and cache Poetry virtualenvs or the pip wheel cache. Caching matters more to wall-clock time than which tool you pick.
The verdict
Want reproducible builds with minimal effort: Poetry. Want the lightest, most universal tool for simple projects: pip with fully pinned requirements. Either way, commit the lockfile and cache it.