Flit vs Poetry: Python Packaging Tools Compared
Choose Flit for simple, pure-Python packages you just want to build and publish; choose Poetry when you also want locked dependencies, virtualenv management, and resolution in one tool.
Flit and Poetry both build and publish Python packages from pyproject.toml, but they target different scopes. Flit is intentionally minimal: it builds and uploads pure-Python packages with almost no configuration. Poetry is a full project and dependency manager with its own resolver, lockfile (poetry.lock), and environment handling.
| Flit | Poetry | |
|---|---|---|
| Scope | Build + publish only | Resolve + lock + venv + build + publish |
| Lockfile | None | poetry.lock |
| Dependency resolver | None (you manage deps) | Built-in resolver |
| Best for | Pure-Python libraries | Apps and libraries with complex deps |
| Config | pyproject.toml ([tool.flit]) | pyproject.toml ([tool.poetry]) |
| Publishing | flit publish | poetry publish |
Where each genuinely wins
Flit wins on simplicity: for a single-module or pure-Python package with no compiled extensions, flit build and flit publish are about as little ceremony as possible. Poetry wins when dependency management matters: it resolves and locks transitive dependencies, manages a virtualenv, and gives a consistent CLI for the whole lifecycle.
In CI
Flit pipelines are tiny: install, flit build, then upload an artifact. Poetry pipelines benefit from poetry install restoring an exact environment from poetry.lock, which makes builds reproducible across runners. If you only publish a simple package, Flit means fewer moving parts in CI.
Honest caveats
Flit is not the right tool for projects with many dependencies or non-trivial build steps, since it does no resolution or locking. Poetry historically diverged from some PEP metadata standards and its resolver could be slow on large graphs, though it has improved; newer tools (uv, PDM) compete directly on speed.
The verdict
Pick Flit for minimal, pure-Python packages where you want the least tooling possible. Pick Poetry when you need dependency resolution, a lockfile, and environment management, not just packaging.