Python Processor#

Annotated Python Processor editor
Modifies incoming continuous data and handles events and spikes using custom code written in Python.#

Plugin Type



Windows, Linux, macOS

Built in?


Key Developers

Spencer Blackwood, Anjal Doshi

Source Code


Installing and upgrading#

The Python Processor is not included by default in the Open Ephys GUI. To install, use ctrl-P or ⌘P to open the Plugin Installer, browse to the “Python Processor” plugin, and click the “Install” button.

The Plugin Installer also allows you to upgrade to the latest version of this plugin, if it’s already installed.

Setting up a Python environment#

This plugin must be able to find a local installation of Python version 3.10 with numpy installed correctly.

To avoid conflicts with other Python installations, we recommend using Conda to manage your Python environments. You can install Conda either using Miniconda or Anaconda by following the instructions here. More information on how to use Conda can be found here.


On macOS, conda needs to be installed using the x86_64 Miniconda / Anaconda installer.

To create a new Conda environment that uses Python 3.10, enter the following conda command in your Anaconda prompt (Windows) or Terminal (Linux and macOS):

conda create -n oe-python-plugin python=3.10

This will create a new Conda environment with Python 3.10 installed. Then, activate this newly created environment like so:

conda activate oe-python-plugin

After this, numpy needs to be installed in the same environment as follows:

conda install numpy


On Windows, if you use pip to install Python packages, the plugin will fail to load your Python module. We are still investigating the cause of this issue.

Setting the Python Interpreter Path#

Once a dedicated Python 3.10 Conda environment has been created, the plugin is ready to be loaded into any desired signal chain. As soon as the plugin is dropped into the signal chain, it asks for the path to Python Home directory, which is where the Python Interpreter is located. This allows the plugin to be flexible in terms of which Python libraries to use during runtime, and not rely on the system PATH to figure out the Python Home location.

When using Conda, this path is usually where the Conda environment got created. Some examples of where it may be located:

  • Windows: C:\Users\<username>\miniconda3 or C:\miniconda3

  • macOS - ~/miniconda3 or /Users/<username>/miniconda3

  • Linux - ~/miniconda3 or /home/<username>/miniconda3

The Python image in a Conda environment called “oe-python-plugin” might be in a location such as ${USERHOME}\miniconda3\envs\oe-python-plugin

If you have installed Anaconda instead of Miniconda, the folder might be named Anaconda or Anaconda3.

Once the path is selected, the plugin should load into the signal chain successfully. If it fails to load the Python Interpreter, then it will ask for the PATH to Python Home again. This means that either the provided PATH was incorrect, or an incompatible version of Python was installed (i.e., not 3.10). If this happens, it is recommended to close and relaunch the GUI to reset the PATH variables.

Creating & loading a Python Module#

Once the plugin is loaded into the signal chain, a Python module (script) needs to be loaded into the GUI. This module should take the same form as the processor template provided in the plugin’s GitHub repository. The PyProcessor class is designed to expose the following functions to the Python module to allow interaction with the incoming data:

__init__(processor, num_channels, sample_rate)#

A new processor is initialized when the module is imported/reloaded, or the plugin’s settings are updated (i.e., the number of input channels changes, or a new stream is selected).

  • processor (object) – Python Processor class object used for adding events from python.

  • num_channels (int) – number of input channels from the selected stream

  • sample_rate (float) – the selected stream’s sample rate


Process each incoming data buffer. Any modifications to the data variable will be passed to downstream processors.


data (ndarrary) – N x M numpy array, where N = num_channles, M = num of samples in the buffer.


Called before starting acquisition. Allows the script to do some setup/initialization before acquisition starts.


Called after stopping acquisition. Allows the script to do some finalization after acquisition stops.


Called before starting recording. Informs the plugin that the GUI is now recording data, in case it needs to save any information of its own.


recording_dir (str) – directory where recording related files are supposed to be stored


Called before stopping recording. Informs the plugin that the GUI is no longer recording data.

handle_ttl_event(source_node, channel, sample_number, line, state)#

Handle each incoming ttl event.

  • source_node (int) – id of the processor this event was generated from

  • channel (str) – name of the event channel

  • sample_number (int) – sample number of the event

  • line (int) – the line on which event was generated (0-255)

  • state (bool) – event state True (ON) or False (OFF)

handle_spike(source_node, electrode_name, num_channels, num_samples, sample_number, sorted_id, spike_data)#

Handle each incoming spike.

  • source_node (int) – id of the processor this spike was generated from

  • electrode_name (str) – name of the electrode

  • num_channels (int) – number of channels associated with the electrode type

  • num_samples (int) – total number of samples in the spike waveform

  • sample_number (int) – sample number of the spike

  • sorted_id (int) – the sorted ID for this spike

  • spike_data (ndarrary) – waveform as N x M numpy array, where N = num_channels & M = num_samples (read-only).

Using this template, any type of data processing can be done in Python in real-time. The data buffer should be overwritten with the new processed data, which will be received by downstream processors.


Pay careful attention to the latency introduced by processing data in Python, especially with high-channel-count data.

There is also a way to send TTL events back from Python to C++. These events will be added to the event buffer for the downstream processors to handle. It is possible using a C++ function exposed to the Python module via an embedded module called oe_pyprocessor.

add_python_event(line, state)#

Send TTL event from Python to C++

  • line (int) – event line number [0-255]

  • state (bool) – event state True (ON) or False (OFF)

To use this function, the oe_pyprocessor module needs to be imported inside the script and then the C++ function can be invoked by using the processor object provided in the __init__() method, like this: self.processor.add_python_event(line, state)

An example script is provided in the plugin’s GitHub repository in the form of a Butterworth Bandpass filter. This filter is the same as the one used in the GUI’s built-in Filter Node plugin.


  • Unlike continuous data and events, sending spikes back from Python is not currently possible.

  • Only one instance of the plugin is allowed at a time in a signal chain. Having multiple instances of the plugin in the same signal chain will result in random crashes.

  • Creating visualizations in real-time using Python libraries such as matplotlib is not possible.