Tasks#

Task is a fundamental building block and an extension point of Flyte, which encapsulates the users’ code. They possess the following properties:

  1. Versioned (usually tied to the git sha)

  2. Strong interfaces (specified inputs and outputs)

  3. Declarative

  4. Independently executable

  5. Unit testable

A task in Flytekit can be of two types:

  1. A task that has a Python function associated with it. The execution of the task is equivalent to the execution of this function.

  2. A task that doesn’t have a Python function, e.g., an SQL query or any portable task like Sagemaker prebuilt algorithms, or a service that invokes an API.

Flyte provides multiple plugins for tasks, which can be a backend plugin as well (Athena).

In this example, you will learn how to write and execute a Python function task. Other types of tasks will be covered in the later sections.

For any task in Flyte, there is one necessary import, which is:

from flytekit import task

A PythonFunctionTask must always be decorated with the @task flytekit.task() decorator. The task in itself is a regular Python function, although with one exception: it needs all the inputs and outputs to be clearly annotated with the types. The types are regular Python types; we’ll go over more on this in the type-system section.

@task
def square(n: int) -> int:
    """
     Parameters:
        n (int): name of the parameter for the task will be derived from the name of the input variable
               the type will be automatically deduced to be Types.Integer

    Return:
        int: The label for the output will be automatically assigned and type will be deduced from the annotation

    """
    return n * n

In this task, one input is n which has type int. The task square takes the number n and returns a new integer (squared value).

Note

Flytekit will assign a default name to the output variable like out0. In case of multiple outputs, each output will be numbered in the order starting with 0, e.g., -> out0, out1, out2, ....

You can execute a Flyte task as any normal function.

if __name__ == "__main__":
    print(square(n=10))

Invoke a Task within a Workflow#

The primary way to use Flyte tasks is to invoke them in the context of a workflow.

from flytekit import workflow


@workflow
def wf(n: int) -> int:
    return square(n=square(n=n))

In this toy example, we’re calling the square task twice and returning the result.

Total running time of the script: ( 0 minutes 0.000 seconds)

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