.. _`Filter List Predicate`:

.. _`org.sysess.sympathy.list.filterlistpredicate`:

Filter List Predicate
`````````````````````

.. image:: filter_list.svg
   :width: 48


Filter a list using a configured item-based predicate.




Documentation
:::::::::::::

This node takes a predicate function (a function that returns True or
False) from the configuration and uses it to decide which inputs to include
in the output.

The function is applied once for each input element in the list and for
each element where the function returned True the element is also included
in the output.

Examples with port type == [table] and item type == table:

Propagate tables with at least 10 rows to output::

    lambda item: item.number_of_rows() >= 10

Propagate only non-empty tables::

    lambda item: not item.is_empty()

The name of the argument is not important.

See https://docs.python.org/3/tutorial/controlflow.html#lambda-expressions
for a description of lambda functions. Have a look at the :ref:`Data type
APIs<datatypeapis>` to see what methods and attributes are available on the
data type that you are working with.


Definition
::::::::::


Input ports
...........

    **list**  [<a>]
        List


Output ports
............

    **index**  table
        Index

    **list**  [<a>]
        List




Configuration
.............

    **Filter function** (predicate)
        Function, called for each item in `list` to determine which inputs to filter. Should return a boolean





Related nodes
.............

* :ref:`org.sysess.sympathy.list.filterlisttable`




Examples
........

* :download:`Predicates.syx </Examples/Sympathy/Generic/List/Predicates.syx>`




Implementation
..............

.. automodule:: node_filter_list
    :noindex:

.. class:: FilterListPredicate
    :noindex: