Extensions

With a Qudi extension it is possible to add custom gui, logic and hardware modules as well as interfaces.

A Qudi extension is a python package with gui, logic and hardware subpackages. All modules in those subpackages are combined in qudi's gui, logic and hardware namespaces, respectively.

Example:

Folder structure:

• my_qudi_extension
  • hardware
    • my_hardware_module.py

After addition of the extension to qudi the module my_hardware_module will be available in the hardware namespace, i.e. as hardware.my_hardware_module. You can import it by

import hardware.my_hardware_module

Please note:

• The shared gui, logic and hardware namespaces mean that if a module with the same name is defined twice, only the one that is found first, will be loaded. For the search order please see below.
• You are not allowed to use __init__.py files within the qudi extension. This is a requirement posed by the implicit namespaces introduced in python 3.3 which we use for extensions.

Adding extensions to Qudi

There are two ways to add an extension to Qudi:

1. In the configuration file
2. PYTHONPATH environment variable

In a configuration file an extension can be added by defining its directory to the extensions key in the global section.

global:
    extensions:
        - "path_to_extension_1"
        - "path_to_extension_2"

The path to the extension can be absolute or relative to the location of the configuration file. If the directory cannot be found an error is thrown and it is ignored.

An extension can also be added by defining its path to the PYTHONPATH environment variable. One way to do this is to start Qudi by PYTHONPATH="path_to_extension_1" python qudi/start.py

The search order is

1. Qudi directory (gui, logic, hardware)
2. Paths defined in the configuration file in the specified order
3. Paths defined in PYTHONPATH in the specified order