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[Pre-alpha] Janis: an open source tool to machine generate type-safe CWL and WDL workflows
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Janis (Pre-alpha)

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Janis is a framework creating specialised, simple workflow definitions that are then transpiled to
Common Workflow Language or Workflow Definition Language.

Documentation is hosted here:


WARNING: this project is work-in-progress and is provided as-is without warranty of any kind. There may be breaking changes committed to this repository without notice.

Janis gives you an API to build computational workflows and will generate a workflow description in CWL and WDL. By using Janis, you get type-safety, portability and reproducibility across all of your execution environments.

Janis requires a Python installation > 3.6, and can be installed through PIP (project page):

# Install janis and the bioinformatics tools
pip3 install janis-pipelines[bioinformatics]  

You can import Janis into your project with:

import janis as j  


Janis is structured into components:

  • core - contains classes and functions to assist in the workflow building.
    • bioinformatics - has bioinformatics tools and data types (import janis.bioinformatics )
    • unix - Installed by default (import janis.unix)
  • runner - An assistant to run Janis workflows using different workflow engines with common semantics.

This repository manages the dependencies for installation and drives the documentation.


Further information: Simple Workflow

Below we've constructed a simple example that takes a string input, calls the echo tool and exposes the Echo tool's output as a workflow output.

import janis as j
from import Echo

w = j.Workflow("workflowId")

inp = j.Input("inputIdentifier", data_type=j.String(), value="Hello, World!")
echo = j.Step("stepIdentifier", tool=Echo())
out = j.Output("outputIdentifier")

    (inp, echo.inp),  # Connect 'inp' to 'echostep'
    (echo.out, out),  # Connect output of 'echostep' to 'out'

# Will print the CWL, input file and relevant tools to the console
w.translate("cwl", to_disk=False)  # or "wdl"

We can export a CWL representation to the console using .translate("cwl"). By including the to_disk=True parameter, we can write this workflow to disk at the current location.

More examples


Janis has an API that mirrors the workflow concepts:

  • j.Workflow: A workflow represents the Edges between Input, Step, Output

    • j.Input: An input to a Workflow, has an identifier, a type and a value.
    • j.Step: A step also has an identifier and a Tool (CommandTool or a nested Workflow).
    • j.Output: An output to a workflow has an identifier and is connected to a step.
  • j.CommandTool: A command line style tool that builds it's command through the inputs and arguments.

    • j.ToolInput: An input to a tool, has an identifier, a type and command line options like position, prefix
    • j.ToolArgument: An argument to a tool that cannot be overridden. Has a value and command line options like position and prefix. The value can be a derived type, like an InputSelector or StringFormatter.
    • j.ToolOutput: Output to a tool, has an identifier, a type and a glob.


Further information: About

This project was produced as part of the Portable Pipelines Project in partnership with:


Through conference or talks, this project has been referenced by the following titles:

  • Walter and Eliza Hall Institute Talk (WEHI) 2019: Portable Pipelines Project: Developing reproducible bioinformatics pipelines with standardised workflow languages
  • Bioinformatics Open Source Conference (BOSC) 2019: Janis: an open source tool to machine generate type-safe CWL and WDL workflows
  • Victorian Cancer Bioinformatics Symposium (VCBS) 2019: Developing portable variant calling pipelines with Janis



Further information: Development

This project is work-in-progress and is still in developments. Although we welcome contributions, due to the immature state of this project we recommend raising issues through the Github issues page for Pipeline related issues.

Information about the project structure and more on contributing can be found within the documentation.

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