Overview
Pluginlib makes creating plugins for your project simple.
Step 1: Define plugin parent classes
All plugins are subclasses of parent classes. To create a parent class, use the
@Parent
decorator.
The @Parent
decorator can take a plugin type for accessing child plugins
of the parent. If a plugin type isn’t given, the class name will be used.
The @Parent
decorator can also take a group
keyword which
restricts plugins to a specific plugin group. group
should be specified if plugins for
different projects could be accessed in an single program, such as with libraries and frameworks.
For more information, see the Plugin Groups section.
Methods required in child plugins should be labeled as abstract methods. Plugins without these methods or with parameters that don’t match, will not be loaded. For more information, see the Abstract Methods section.
"""
sample.py
"""
import pluginlib
@pluginlib.Parent('parser')
class Parser(object):
@pluginlib.abstractmethod
def parse(self, string):
pass
Step 2: Define plugin classes
To create a plugin, subclass a parent class and include any required methods.
Plugins can be customized through optional class attributes:
_alias_
Changes the name of the plugin which defaults to the class name.
_version_
Sets the version of the plugin. Defaults to the module
__version__
orNone
. If multiple plugins with the same type and name are loaded, the plugin with the highest version is used. For more information, see the Versions section._skipload_
Specifies the plugin should not be loaded. This is useful when a plugin is a parent class for additional plugins or when a plugin should only be loaded under certain conditions. For more information see the Conditional Loading section.
"""
sample_plugins.py
"""
import json
import sample
class JSON(sample.Parser):
_alias_ = 'json'
def parse(self, string):
return json.loads(string)
Step 3: Load plugins
Plugins are loaded when the module they are in is imported. PluginLoader
will load modules from specified locations and provides access to them.
PluginLoader
can load plugins from several locations.A program’s standard library
A list of modules
A list of filesystem paths
Plugins can also be filtered through blacklists and type filters. See the Blacklists and Type Filters sections for more information.
Plugins are accessible through the PluginLoader.plugins
property,
a nested dictionary accessible through dot notation. For other ways to access plugins,
see the Accessing Plugins section.
import pluginlib
import sample
loader = pluginlib.PluginLoader(modules=['sample_plugins'])
plugins = loader.plugins
parser = plugins.parser.json()
print(parser.parse('{"json": "test"}'))