Tasks

Tags: Basic

A task serves as the fundamental building block and an extension point within Flyte. It exhibits the following characteristics:

1. Versioned (typically aligned with the git sha)

2. Strong interfaces (annotated inputs and outputs)

3. Declarative

4. Independently executable

5. Suitable for unit testing

A Flyte task operates within its own container and runs on a Kubernetes pod. It can be classified into two types:

1. A task associated with a Python function. Executing the task is the same as executing the function.

2. A task without a Python function, such as a SQL query or a portable task like prebuilt algorithms in SageMaker, or a service calling an API.

Flyte offers numerous plugins for tasks, including backend plugins like Athena.

This example demonstrates how to write and execute a Python function task.

Note

To clone and run the example code on this page, see the Flytesnacks repo.

To begin, import task from the flytekit library:

basics/task.py

from flytekit import task

The use of the task() decorator is mandatory for a PythonFunctionTask. A task is essentially a regular Python function, with the exception that all inputs and outputs must be clearly annotated with their types. Learn more about the supported types in the type-system section.

We create a task that computes the slope of a regression line:

basics/task.py

@task
def slope(x: list[int], y: list[int]) -> float:
    sum_xy = sum([x[i] * y[i] for i in range(len(x))])
    sum_x_squared = sum([x[i] ** 2 for i in range(len(x))])
    n = len(x)
    return (n * sum_xy - sum(x) * sum(y)) / (n * sum_x_squared - sum(x) ** 2)

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 just like any regular Python function:

basics/task.py

if __name__ == "__main__":
    print(slope(x=[-3, 0, 3], y=[7, 4, -2]))

Note

When invoking a Flyte task, you need to use keyword arguments to specify the values for the corresponding parameters.

To run it locally, you can use the following pyflyte run command:

pyflyte run \
  https://raw.githubusercontent.com/flyteorg/flytesnacks/master/examples/basics/basics/task.py \
  slope --x '[-3,0,3]' --y '[7,4,-2]'

If you want to run it remotely on the Flyte cluster, simply add the --remote flag to the pyflyte run command:

pyflyte run --remote \
  https://raw.githubusercontent.com/flyteorg/flytesnacks/master/examples/basics/basics/task.py \
  slope --x '[-3,0,3]' --y '[7,4,-2]'