lenskit.metrics.basic.ListLength
================================

.. py:class:: lenskit.metrics.basic.ListLength
   

   Bases: :py:obj:`lenskit.metrics._base.ListMetric`


   Report the length of the output (recommendation list or predictions).

   :Stability: Caller


   .. py:attribute:: label
      :value: 'N'


      The metric's default label in output.
      The base implementation returns the class name by default.


   .. py:method:: measure_list(recs, test)

      Compute measurements for a single list.

      :returns:

                - A float for simple metrics
                - Intermediate data for decomposed metrics
                - A dict mapping metric names to values for multi-metric classes