Dagger Python SDK

A client package for running Dagger pipelines.

What is the Dagger Python SDK?

The Dagger Python SDK contains everything you need to develop CI/CD pipelines in Python, and run them on any OCI-compatible container runtime.

Requirements

• Python 3.10 or later
• Docker, or another OCI-compatible container runtime

A compatible version of the Dagger CLI is automatically downloaded and run by the SDK for you, although it’s possible to manage it manually.

Installation

From PyPI, using pip:

pip install dagger-io

You can also install via Conda, from the conda-forge channel:

conda install dagger-io

Example

Create a main.py file:

import sys

import anyio
import dagger
from dagger import dag


async def main(args: list[str]):
    async with dagger.connection():
        # build container with cowsay entrypoint
        ctr = (
            dag.container()
            .from_("python:alpine")
            .with_exec(["pip", "install", "cowsay"])
            .with_entrypoint(["cowsay"])
        )

        # run cowsay with requested message
        result = await ctr.with_exec(args).stdout()

    print(result)


anyio.run(main, sys.argv[1:])

Run with:

$ python main.py "Simple is better than complex"
  _____________________________
| Simple is better than complex |
  =============================
                             \
                              \
                                ^__^
                                (oo)\_______
                                (__)\       )\/\
                                    ||----w |
                                    ||     ||

Note It may take a while for it to finish, especially on first run with cold cache.

If you need to debug, you can stream the logs from the engine with the log_output config:

config = dagger.Config(log_output=sys.stderr)
async with dagger.connection(config):
    ...

Learn more

• Documentation
• API Reference
• Source code

Development

The SDK is managed with a Dagger module in ./dev. To see which tasks are available run:

dagger call -m dev

Common tasks

Run pytest in supported Python versions:

dagger call -m dev tests

Check for linting violations:

dagger call -m dev lint check

Re-format code following common styling conventions:

dagger call -m dev lint format -o .

Update pinned devevelopment dependencies:

dagger call -m dev lock -o .

Build and preview the reference documentation:

dagger call -m dev docs preview up

Add --help to any command to check all the available options.

Engine changes

Testing and regenerating the client may fail if there’s changes in the engine code that haven’t been released yet. Prefix with hack/dev to build a new engine before executing pipelines:

../../hack/dev dagger call -m dev test

To re-generate the client (codegen) after changes to the API schema:

./hack/dev ./hack/make sdk:python:generate