# Plugin system¶

This page explains how to contribute to the plugin system in aiida-core. For instrucions on how to develop plugins, see 如何打包插件.

## Design Principles¶

1. Only restrict plugin developers when really necessary;

2. Avoid database schema changes whenever reasonably possible;

3. Finding and loading plugins must be as fast as the plugin allows, especially for command line interface (CLI) commands. In other words, directly importing a plugin class should not be noticeably faster than using the plugin loader/factory;

4. Implement as a drop-in replacement, provide backwards compatibility to pre-0.9 plugin system;

5. Plugin management should be as user friendly from the verdi shell as from the CLI.

## Mini-Spec¶

### Nomenclature¶

plugin_name

A unique name identifying the plugin. Suggested naming scheme is

• aiida-<plugin-name> for pypi distribution / source code repository

• aiida_<plugin_name> for python package (import aiida_<plugin_name>; dashes replaced by underscores)

• <plugin_name>.ep_name for entry points

category

A name given to each aspect of AiiDA that can be extended via plugins, such as calculations, schedulers, … (see output of verdi plugin list for a complete list).

Each category maps to an entry point group aiida.<category>.

### Interfaces¶

The plugin loading functionality is defined in aiida.plugins.entry_point and relies on the reentry package to find and load entry points. reentry is about 10x faster than the equivalent functionality in pkg_resources from setuptools, leading to significant speedup of tab-autocompletion in the verdi cli. If, for some reason, reentry is not found, the plugin system falls back on pkg_resources.
See the API documentation in aiida.plugins.