Inline Plugin
=============

The ``inline`` plugin lets you use Python to customize your path formats. Using
it, you can define template fields in your beets configuration file and refer to
them from your template strings in the ``paths:`` section (see
:doc:`/reference/config/`).

To use the ``inline`` plugin, enable it in your configuration (see
:ref:`using-plugins`). Then, make a ``item_fields:`` block in your config file.
Under this key, every line defines a new template field; the key is the name of
the field (you'll use the name to refer to the field in your templates) and the
value is a Python expression or function body. The Python code has all of a
track's fields in scope, so you can refer to any normal attributes (such as
``artist`` or ``title``) as Python variables.

Here are a couple of examples of expressions:

::

    item_fields:
        initial: albumartist[0].upper() + u'.'
        disc_and_track: f"{disc:02d}.{track:02d}" if disctotal > 1 else f"{track:02d}"

Note that YAML syntax allows newlines in values if the subsequent lines are
indented.

These examples define ``$initial`` and ``$disc_and_track`` fields that can be
referenced in path templates like so:

::

    paths:
        default: $initial/$artist/$album%aunique{}/$disc_and_track $title

Block Definitions
-----------------

If you need to use statements like ``import``, you can write a Python function
body instead of a single expression. In this case, you'll need to ``return`` a
result for the value of the path field, like so:

::

    item_fields:
        filename: |
            import os
            from beets.util import bytestring_path
            return bytestring_path(os.path.basename(path))

You might want to use the YAML syntax for "block literals," in which a leading
``|`` character indicates a multi-line block of text.

Album Fields
------------

The above examples define fields for *item* templates, but you can also define
fields for *album* templates. Use the ``album_fields`` configuration section. In
this context, all existing album fields are available as variables along with
``items``, which is a list of items in the album.

This example defines a ``$bitrate`` field for albums as the average of the
tracks' fields:

::

    album_fields:
        bitrate: |
            total = 0
            for item in items:
                total += item.bitrate
            return total / len(items)
