Define a lambda/callable entity ############################### This step will help you define an entity referring to a callable object. First, we create a callable ``write_json`` at ``app/func.py``: .. code-block:: python def write_json(where, content): with open(where, 'w') as f: f.write(content) Then, register this class as a lambda/callable entity in ``containers.xml``: .. code-block:: xml Now, you have an entity called **happy_panda.write_to_file**. We call this a lambda (or callable) entity (see more at :doc:`../definitions`). .. warning:: This type of entities does not allow parameters as the entity directly refers to a callable object. How to work with the first-place report entity ============================================== To refer the first-place report entity, for example, in ``main.py``, simply do: .. code-block:: python # Omitted the code for main.py already shown above write = assembler.core.get('happy_panda.write_to_file') .. tip:: For more information about the DTD of the configuration file, please check out `the DTD `_ on GitHub. Next step? :doc:`07-aspect-oriented-programming`.