Parsl - Parallel Scripting Library

Parsl is a Python library for programming and executing data-oriented workflows (dataflows) in parallel. Parsl scripts allow selected Python functions and external applications (called apps) to be connected by shared input/output data objects into flexible parallel workflows. Rather than explicitly defining a dependency graph and/or modifying data structures, instead developers simply annotate Python functions and Parsl constructs a dynamic, parallel execution graph derived from the implicit linkage between apps based on shared input/output data objects. Parsl then executes apps when dependencies are met. Parsl is resource-independent, that is, the same Parsl script can be executed on a laptop, cluster, cloud, or supercomputer.

Parsl can be used to realize a variety of workflows:

  • Parallel dataflow in which tasks are executed when their dependencies are met.
  • Interactive and dynamic workflows in which the workflow is dynamically expanded during execution by users or the workflow itself.
  • Procedural workflows in which serial execution of tasks are managed by Parsl.


Parsl collects anonymous usage statistics for reporting and improvement purposes. To understand what stats are collected and to disable collection please refer to the usage tracking guide

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