nextflow.py

nextflow.py is a Python wrapper around the Nextflow pipeline framework. It lets you run Nextflow pipelines from Python code.

import nextflow

pipeline = nextflow.Pipeline("main.nf")
execution = pipeline.run(params={"param1": "123"})
print(execution.status)

Installation

nextflow.py is available through PyPI:

pip install nextflow

You must install the Nextflow executable itself separately: see the Nextflow Documentation for help with this.

Use

The starting point for any nextflow.py pipeline is the Pipeline object. This is initialised with a path to the file in question, and, optionally, the location of an accompanying config file and input schema (formatted acording to nf-core) guidelines:

pipeline1 = nextflow.Pipeline("pipelines/my-pipeline.nf")
pipeline2 = nextflow.Pipeline("main.nf", config="nextflow.config", schema="inputs.json")

These are executed with the run() method. Arguments are:

• location (default ".") - the directory the pipeline will be run from. This is where the work directory will be created, and where the log file will be written to.

• params (default None) - any inputs to be passed to the pipeline at runtime as a Python dictionary.

• profile (default None) - any settings profiles to apply, as a list of profile names.

execution1 = pipeline1.run()
execution2 = pipeline2.run(location="./rundir", params={"param1": "123"}, profile=["docker", "test"])

Upon completion you get an Execution object back. This is a record of the execution that just ran, and you can interrogate various properties from it:

• id - The unique ID of that run, generated by Nextflow.

• datetime - When the pipeline ran.

• duration - how long the execution took.

• status - the status Nextflow reports on completion.

• command - the command used to run the pipeline.

• log - the full text of the log file produced.

• process_executions - the associated ProcessExecution objects.

A ProcessExecution is the record of the execution of a specific process within the overall Pipeline execution. The precise attributes are generated automatically at runtime based on the output of nextflow log, but some useful ones are:

• process - the process's name within Nextflow.

• name - the unique name for this process execution.

• stdout - the process's text output.

• stderr - the process's error text output.

You can get all of the descriptive data at once with the fields attribute.

Changelog

0.1.4

12th January, 2022

• Pipeline command generation no longer applies quotes if there are already quotes.

0.1.3

24th November, 2021

• Fixed Windows file separator issues.
• Renamed NextflowProcess -> ProcessExecution.

0.1.2

3rd November, 2021

• Better handling of missing Nextflow executable.

0.1.1

29th October, 2021

• Renamed nextflow_processes to process_executions.

• Added quotes around paths to handle spaces in paths.

0.1

18th October, 2021

• Basic Pipeline object.

• Basic Execution object.

• Basic ProcessExecution object.