.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "starterkit/Ex03_basics_b2luigi_wrappertask.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_starterkit_Ex03_basics_b2luigi_wrappertask.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_starterkit_Ex03_basics_b2luigi_wrappertask.py:


.. _exercise03_label:

``b2luigi.WrapperTask`` and ``b2luigi`` Settings
================================================

.. hint::
    This example demonstrates the usage of the ``b2luigi.WrapperTask`` class.
    This class is used to define a task that requires multiple other tasks to be executed.
    At the end of this section, we introduce the ``b2luigi`` settings mechanism.

The :class:`b2luigi.WrapperTask` class is used to define a task that requires all parameter combinations of another task to be executed.
The combinations are determined by the ``requires`` method of the :class:`b2luigi.WrapperTask`.

To show the functionality of the :class:`b2luigi.WrapperTask` class, we will create a third task that depends on second task and executes all parameter combinations of the second task.
For this, we define the first and second task in the same way as in the previous example.

.. GENERATED FROM PYTHON SOURCE LINES 18-50

.. code-block:: Python


    import b2luigi


    class MyTask(b2luigi.Task):
        parameter = b2luigi.IntParameter()

        def run(self):
            with open(self.get_output_file_name("output.txt"), "w") as f:
                f.write(f"{self.parameter}")

        def output(self):
            yield self.add_to_output("output.txt")


    class MyOtherTask(b2luigi.Task):
        parameter = b2luigi.IntParameter()

        def requires(self):
            return MyTask(parameter=self.parameter)

        def output(self):
            yield self.add_to_output("output2.txt")

        def run(self):
            with open(self.get_input_file_names("output.txt")[0], "r") as f:
                number = int(f.read())

            with open(self.get_output_file_name("output2.txt"), "w") as f:
                f.write(f"{number**2}")



.. GENERATED FROM PYTHON SOURCE LINES 51-54

Here, we define the ``b2luigi.WrapperTask`` to loop over all parameter combinations of the second task.
In contrast to the usual :class:`b2luigi.Task` class, it does not need a ``run`` and ``output`` method.
The task counts as completed if its requirement is fulfilled.

.. GENERATED FROM PYTHON SOURCE LINES 57-64

.. code-block:: Python

    class MyWrapperTask(b2luigi.WrapperTask):
        max_value = b2luigi.IntParameter()

        def requires(self):
            return [MyOtherTask(parameter=value) for value in range(self.max_value)]



.. GENERATED FROM PYTHON SOURCE LINES 65-77

We make use of the settings mechanism of ``b2luigi`` to define the directory where the results will be stored.
This is done by assigning a value to the `result_dir` key.
Setting the `results_dir` here, globally, will now save all the outputs of the processed tasks in the specified location.
It is also possible to define for each task specifically the settings.
The order in which the settings are respected is as follows:

- Task instance attribute
- Task class property
- Global setting (as demonstrated here)
- Configuration file 'settings.json'

More information about the settings can be found in the :ref:`settings-label` section.

.. GENERATED FROM PYTHON SOURCE LINES 79-83

.. code-block:: Python

    if __name__ == "__main__":
        b2luigi.set_setting("result_dir", "results")
        b2luigi.process(MyWrapperTask(max_value=10))


.. GENERATED FROM PYTHON SOURCE LINES 84-97

Check the output with:

.. code-block:: bash

  for file in results/*/output2.txt; do cat "$file"; echo ""; done

In very easy cases, it is also possible to directly process a list of
tasks at this position. However, this is not recommended for more complex
task trees. The equivalent process call would be:

.. code-block:: python

  b2luigi.process([MyOtherTask(parameter=value) for value in range(10)])


.. _sphx_glr_download_starterkit_Ex03_basics_b2luigi_wrappertask.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: Ex03_basics_b2luigi_wrappertask.py <Ex03_basics_b2luigi_wrappertask.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: Ex03_basics_b2luigi_wrappertask.zip <Ex03_basics_b2luigi_wrappertask.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_