The Expyriment plugin system (extras)


The design, stimuli, io and misc packages can be extended with plugins (additional classes) that can be accessed via the ‘extras’ namespace of each package. Expyriment will look for installed plugins in the following locations within the .expyriment/extras (or ~expyriment/extras) directory located in the current user’s home directory:

  • expyriment_extras_design
  • expyriment_extras_stmuli
  • expyriment_extras_io
  • expyriment_extras_misc

Any plugins found will be integrated into the .extras namespace of each package (e.g. expyriment.stimuli.extras.DotCloud).

There are three ways to import extras:

  1. Import all extras in one go:

    import expyriment
  2. Import all extras from a specific package:

    import expyriment
    import expyriment.stimuli.extras
  3. Import a specific plugin:

    import expyriment
    from expyriment_stimuli_extras.dotcloud import DotCloud

Download plugins from stash

Several extra plugins can be found in the Expyriment stash. When Expyriment has been installed with the option download (or all), all plugins can be downloaded automatically by calling:


Alternatively, you can use the Command Line Interface:

expyriment -D


When developing extra plugins, please consider making them available publicly in the Expyriment stash, by creating a pull request.

Basically, extra plugins are a simple Python module with a single class, where the filename is the class name in lowercase. Additionally a file called can be created which will hold the default values for all parameters given when initializing the class. The naming convention is classname_parameter.

For design and misc extras this is all there is, but for io and stimuli plugins, additional conventions need to be taken care of.


IO plugins have to inherit from or or both. This means they can also inherit from any other io class.


Stimulus plugins have to inherit from expyriment.stimuli.Stimulus. This means they can also inherit from any other stimulus class. Additionally, every visual extra stimulus class (inherited from expyriment.stimuli.Visual) needs a _create_surface method that defines what happens when the stimulus is preloaded, plotted or presented.