This section is about creating and developing libraries. For introductory information about libraries and their use see Using Libraries.

Creating new libraries

When Sympathy starts it looks for nodes in all library folders, seen in Node Libraries Preferences and to create your own node or plugins, first you have to create a library and add it to Sympathy’s list of libraries.

To create a library all you need to do is use the Library Wizard. Start it by clicking File -> Wizards -> New Library.

On the first page you will add some meta data about your library. Only name and identifier are mandatory, but go ahead and add as much as you can!

On the second page you will select the path where the library will be saved, and a preview of the folders and files created will be displayed. You can change the Package name (symbolizied by <package-name> in the following sections) if you want, but this is not needed.

When you have finished the wizard, the library has been automatically added to Node Libraries Preferences. Note, this is not synonymous with adding libraries to the library view.

New Library Format

Starting with Sympathy 2.0.0 there is a new format for libraries that is more “python-like”. One benefit from the new format is the ability to distribute libraries like any other python package. When you are creating a new library the new format is recommended unless you also need to support older Sympathy versions.

Library structure

This is the new, recommended way to structure a node library:

├── doc
│   └── <package-name>
│       ├── config.ini
│       └── index.rst
├── src
│   └── <package-name>
│       ├──
│       └── library
│           ├── flows
│           │   └── ... (flows)
│           ├── nodes
│           │   └── ... (nodes)
│           ├── plugins
│           │   └── ... (plugins)
│           └── examples
│               └── ... (example flows)
└── test
    ├── flows
    │   └── ... (test flows)
    └── ... (unit tests)

Tests of your library’s functionality should be placed in test and Example flows that show off how your nodes work should be placed in example. Test and examples folders are completely optional.

Library meta data

Meta data fields are defined as functions without arguments.


Tags for organizing nodes in Library View.

Return value and type ommited, see the source for actual values.


Port type definitions.

Return value and type ommited, see the source for actual values.

sympathy.api.library.copyright() str[source]


sympathy.api.library.documentation_url() str[source]

URL to public documentation.

sympathy.api.library.examples_path() str[source]

Path to examples.

sympathy.api.library.flows() List[str][source]

Paths to python files containing flow nodes.

sympathy.api.library.home_url() str[source]

URL to public home page.

sympathy.api.library.icon() str[source]

Path to icon file.

sympathy.api.library.identifier() str[source]

Library identifier, which should be unique. See

sympathy.api.library.maintainer() str[source]

Maintainer. Format Name <email>. str[source]

Library name as shown in Library View, documentation etc.

sympathy.api.library.nodes() List[str][source]

Paths to python files containing nodes.

sympathy.api.library.plugins() List[str][source]

Paths to python files containing node plugins.

sympathy.api.library.repository_url() str[source]

URL to public source repository.

sympathy.api.library.required_features() List[str][source]

Features required for enabling the library.

sympathy.api.library.version() str[source]

Version. Format minor.major.micro

The file in the <package-name> can be edited to customize the meta data for libraries.

Old Library Format

Older library format used in Sympathy before 2.0.0. Recommended if you want the library to be usable from older Sympathy versions.

Library structure

This is the old way to structure a node library:

├─ doc
│  └─ <package-name>
│     ├─ config.ini
│     └─ index.rst
├─ Library
│  └─ <Library-name>
│     └─ ... (nodes & plugins)
├─ Common
│  └─ <package-name>
│     └─ ... (python modules)
├─ Tests
│  ├─ Unit
│  │  └─
│  └─ Workflow
│     └─ ... (test flows)
├─ Examples
└─ library.ini

The Library folder is where you put nodes and plugins. The Common folder is for additional python modules. Tests of your library’s functionality should be placed in Tests and Example flows that show off how your nodes work should be placed in Examples. Tests and Examples folders are completely optional.

Library meta data

The file Library.ini in the library root may contain extra meta data for the library. The following fields are recognized in the General section:


The human readable name of the library.


The human readable description of the library.


And identifier for this library. Should only contain


The path of the library folder relative to the library root.


The path of the package inside the common folder relative to the library root.


The name and contact information of the current maintainer of the libary. Can be an indiviual person, an organisation or a community.


A copyright notice that is shown with all nodes.


The version of the library.


Url to repository for the library).


Url to documentation for the library).


Url to home for the library).

Add extra modules to your library

If your node code is starting to become too big to keep it all in a single file or if you created some nice utility functions that you want to use in several different node files you can place them in the <package-name> folder.

Open your favorite editor and create the file:


The parent of the <package-name> folder will automatically be added to sys.path so you will be able to import modules from that package in your node code:

from <package-name> import mymodule

Library tags

Each library may define additional node tags. These tag definitions go into the file <package_name>/, and it can look something like this:

from sympathy.api.nodeconfig import LibraryTags, TagType, GroupTagType

    # Assuming a new library format.
    # If you use Old Library Format, rename tags() function to library_tags().
def tags():
    return [

class ExamplelibLibraryTags(LibraryTags):
    class_tags = (

            # First group
                         'Tag description'),
                         'Tag description')]

            # Second group
                         'Tag description',
                         name='Optional tag name that can hold non-alphabetic characters')]

            # Third group
                         'Tag description'),
                         'Tag description'),
                         'Tag description')],
                name='Optional group name that can hold non-alphabetic characters')

    def __init__(self):
        self._root = self.class_tags

This will create a structure like below (if using Separated Tag Layout, otherwise the tags will be mixed in with those already existing):

Custom tags example

Note that tags won’t show up in the tree until they are used by at least one node. The tags are searchable when using Wizards to create new nodes.

Example flows

Workflows in the Examples directory (create it, if it does not exist, before adding example flows) of a library will be treated as examples.

Example flows are treated similarly to test workflows in that they are executed automatically when running the built-in test suite. See Writing tests for your nodes.

Additionally, example flows can specify (on the top-level) that they are examples for one or several nodes by including a reference in the following format: Node example: *<node-identifier>* (for example, Node example: *com.example.boblib.helloworld*) inside text fields. Alternatively, to make the example reference fit better as part of a sentence, the following format is also supported: Node example for *<node-identifier>*.

The documentation for referenced nodes will include links to referencing example flows. Example flows are copied into the documentation folder and as a rule, it is best if they are self-contained and do not depend on other workflows or data files.

Documenting Libraries

Sympathy includes a system for building HTML documentation for compliant libraries. The generated documentation includes information about nodes and plugins in the same style as in this documentation. The system internally uses Sphinx to build the documentation, and inherits many of its behaviors and requirements.

See Documenting nodes for information about how to document nodes in a way that is supported by the system.

The documentation can then be built from the command-line:

sympathy doc --library-dir <PATH_TO_NODE_LIB>

Note that <PATH_TO_NODE_LIB> should be a path to <library-root>/src/<package-name> for New Library Format libraries and a path to <library-root> for Old Library Format libraries.

For more information about the different command-line options, see Command options.

If you are distributing your library to other users, consider building its documentation yourself and including that with the distributed library. This will save your end-users the hassle of building the documentation themselves.

The generated library documentation will contain a listing of nodes and plugins with a generic index page. It is also possible to do certain customization of the documentation.


The documentation can be customized with a custom index page, logo, and favicon (tab icon). It is also possible to include additional documents from the index page. Customization is done by adding files under the package’s documentation root folder: <library-root>/doc/<package-name>. See, for example, config.ini or index.rst in Library Structure.

The default filenames for logo and favicon are logo.png and favicon.ico, respectively. To customize logo or favicon filenames, create config.ini and define the new filenames as seen below:

logo = alternative_logo.png
favicon = icons/alternative_favicon.ico

Relative paths with / as separator can be used to refer to files under the package’s documentation root folder. Referenced files needs to be present under the folder.

To customize the index page, create index.rst as seen below:

Example library

:Copyright: |sy_lib_copyright|
:Maintainer: |sy_lib_maintainer|
:Version: |sy_lib_version|

This is the index page of the documentation for the custom `Example library`


.. toctree::
   :maxdepth: 2


The index page (index.rst) should be written in Sphinx compliant reStructuredText format.

You can customize the content of the index page and even add new pages (.rst) and images (.svg, .gif and .png) by placing them under the package’s documentation folder and then referencing them from rst. Note that Library/index.rst is the index for the library nodes, generated by the documentation system and should be present. The Library folder is reserved for generation and should not exist in the folder.

The above index page uses substitution variables sy_lib_copyright, sy_lib_maintainer and sy_lib_version. These will be substituted with the corresponding values (copyright, maintainer and version respectively) from the Library Meta Data, this is not necessary but can be used to avoid duplication.