Nextstrain CLI Development
nextstrain-cli happens at https://github.com/nextstrain/cli.
We currently target compatibility with Python 3.6 and higher.
Versions for this project follow the Semantic Versioning rules.
You can use Pipenv to spin up an isolated development environment:
pipenv sync --dev pipenv run nextstrain --help
The Pipenv development environment includes our dev tools (described below):
pipenv run pytest # runs doctests as well as mypy and flake8 pipenv run mypy nextstrain pipenv run flake8
Running with local changes
From within a clone of the git repository you can run
test your local changes without installing them. (Note that
is not the script that gets installed by pip as
nextstrain; that script is
generated by the
entry_points configuration in
There is a
./devel/release script which will prepare a new release from your
local repository. It ends with instructions for you on how to push the release
commit/tag and how to upload the built distributions to PyPi. You’ll need a
PyPi account and twine installed.
Tests are run with pytest. To run everything, use:
This includes the type annotation and static analysis checks described below.
Type annotations and static analysis
Our goal is to gradually add type annotations to our code so that we can catch errors earlier and be explicit about the interfaces expected and provided. Annotation pairs well with the functional approach taken by the package.
During development you can run static type checks using mypy:
$ mypy nextstrain # No output is good!
$ npx pyright ... Found 40 source files 0 errors, 0 warnings, 0 infos Completed in 2sec
There are also many editor integrations for mypy, and Pyright is integrated into VS Code’s Python support.
typing_extensions module should be used for features added to the
typings module after 3.6.
We also use Flake8 for some static analysis checks focusing on runtime safety and correctness. You can run them like this:
$ flake8 # No output is good!