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Nextstrain command-line tool

Project description

Nextstrain CLI

This is the source code repository for a program called nextstrain, the Nextstrain command-line interface (CLI). It aims to provide a consistent way to run and visualize pathogen builds and access Nextstrain components like Augur and Auspice across computing environments such as Docker, Conda, and AWS Batch.

If you're unfamiliar with Nextstrain builds, you may want to follow our quickstart guide first and then come back here.


The nextstrain program, or command, provides subcommands for building, viewing, and managing Nextstrain pathogen builds.

For details on installation, see below.

usage: nextstrain [-h]

Nextstrain command-line interface (CLI)

The `nextstrain` program and its subcommands aim to provide a consistent way to
run and visualize pathogen builds and access Nextstrain components like Augur
and Auspice across computing environments such as Docker, Conda, and AWS Batch.

optional arguments:
  -h, --help            show this help message and exit

    build               Run pathogen build
    view                View pathogen build
    deploy              Deploy pathogen build
    remote              Upload, download, and manage Nextstrain files on
                        remote sources.
    shell               Start a new shell in the build environment
    update              Update your local image copy
    check-setup         Test your local setup
    version             Show version information

For more information on a specific command, you can run it with the --help option, for example, nextstrain build --help.


Python 3.5 or newer

This program is written in Python 3 and requires at least Python 3.5. There are many ways to install Python 3 on Windows, macOS, or Linux, including the official packages, Homebrew for macOS, and the Anaconda Distribution. Details are beyond the scope of this guide, but make sure you install Python 3.5 or higher. You may already have Python 3 installed, especially if you're on Linux. Check by running python --version or python3 --version.


With Python 3 installed, you can use Pip to install the nextstrain-cli package:

$ python3 -m pip install nextstrain-cli
Collecting nextstrain-cli
[…a lot of output…]
Successfully installed nextstrain-cli-1.16.5

This package also works great with Pipx, a nice alternative to Pip for command-line apps like this one:

$ pipx install nextstrain-cli
Installing to directory '/home/tom/.local/pipx/venvs/nextstrain-cli'
  installed package nextstrain-cli 1.16.5, Python 3.6.9
  These apps are now globally available
    - nextstrain
done! ✨ 🌟 ✨

Either way you choose, make sure the nextstrain command is available after installation by running nextstrain version:

$ nextstrain version
nextstrain.cli 1.16.5

The version you get will probably be different than the one shown in the example above.

Computing environment

The Nextstrain CLI provides a consistent interface for running and visualizing Nextstrain pathogen builds across several different computing environments, such as Docker, Conda, and AWS Batch. Each computing environment provides specific versions of Nextstrain's software components and is responsible for running Nextstrain's programs like Augur and Auspice. For this reason, the different computing environments are called "runners" by the CLI.

At least one of these computing environments, or runners, must be setup in order for many of nextstrain's subcommands to work, such as nextstrain build and nextstrain view.

The default runner is Docker, using the nextstrain/base container image. Containers provide a tremendous amount of benefit for scientific workflows by isolating dependencies and increasing reproducibility. However, they're not always appropriate, so a "native" runner is also supported. The installation and setup of supported runners is described below.


Docker is a very popular container system freely-available for all platforms. When you use Docker with the Nextstrain CLI, you don't need to install any other Nextstrain software dependencies as validated versions are already bundled into a container image by the Nextstrain team.

On macOS, download and install Docker Desktop, also known previously as "Docker for Mac".

On Linux, install Docker with the standard package manager. For example, on Ubuntu, you can install Docker with sudo apt install

On Windows, there are still significant obstacles to running with Docker, as documented in our issue tracking the problems. However, if you have access to WSL2, you should be able to use Docker inside it by following the Linux install instructions. Alternatively, you can use the native or AWS Batch runners.

Once you've installed Docker, proceed with checking your setup.


The "native" runner allows you to use the Nextstrain CLI without installing Docker, for cases when you cannot or do not want to use containers.

However, you will need to make sure all of the Nextstrain software dependencies are available locally or "natively" on your computer. The easiest and most common way to do this is by using Conda to install our Conda environment, as documented here. It is also possible to install the required Nextstrain software Augur and Auspice and their dependencies manually, although this is not recommended.

Once you've installed dependencies, proceed with checking your setup.

AWS Batch

AWS Batch is an advanced computing environment which allows you to launch and monitor Nextstrain builds in the cloud from the comfort of your own computer. The same image used by the local Docker runner is used by AWS Batch, making your builds more reproducible, and builds have access to computers with very large CPU and memory allocations if necessary.

The initial setup is quite a bit more involved, but detailed instructions are available.

Once you've setup AWS, proceed with checking your setup.

Checking your setup

After installation and setup, run nextstrain check-setup --set-default to ensure everything works and automatically pick an appropriate default runner based on what's available. You should see output similar to the following:

$ nextstrain check-setup --set-default
nextstrain-cli is up to date!

Testing your setup…

# docker is supported
✔ yes: docker is installed
✔ yes: docker run works
✔ yes: containers have access to >2 GiB of memory
✔ yes: image is new enough for this CLI version

# native is not supported
✔ yes: snakemake is installed
✘ no: augur is installed
✘ no: auspice is installed

# aws-batch is not supported
✘ no: job description "nextstrain-job" exists
✘ no: job queue "nextstrain-job-queue" exists
✘ no: S3 bucket "nextstrain-jobs" exists

All good!  Supported Nextstrain environments: docker

Setting default environment to docker.

If the output doesn't say "All good!" and list at least one supported Nextstrain computing environment (typically Docker or native), then something may be wrong with your installation.

The default is written to the ~/.nextstrain/config file. If multiple environments are supported, you can override the default for specific runs using command-line options such as --docker, --native, and --aws-batch, e.g. nextstrain build --native ….

Big picture

The Nextstrain CLI glues together many different components. Below is a brief overview of the big picture:

The Nextstrain CLI glues together many components


Development of nextstrain-cli happens at

We currently target compatibility with Python 3.5 and higher. This may be increased to 3.6 in the future.

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 ./bin/nextstrain to test your local changes without installing them. (Note that ./bin/nextstrain is not the script that gets installed by pip as nextstrain; that script is generated by the entry_points configuration in


New releases are made frequently and tagged in git using a signed tag. The source and wheel (binary) distributions are uploaded to the nextstrain-cli project on PyPi.

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!

There are also many editor integrations for mypy.

Note that our goal of compatibility with Python 3.5 means that type comments are necessary to annotate variable declarations:

# Not available in Python 3.5:
foo: int = 3

# Instead, use trailing type hint comments:
foo = 3  # type: int

The typing_extensions module should be used for features added to the standard typings module after 3.5. (Currently this isn't necessary since we don't use those features.)

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!

Project details

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