SlackBuilds.org/python/pluginbase

PluginBase is a module for Python that enables the development of
flexible plugin systems in Python.

Step 1:
from pluginbase import PluginBase
plugin_base = PluginBase(package='yourapplication.plugins')

Step 2:
plugin_source = plugin_base.make_plugin_source(
searchpath=['./path/to/plugins', './path/to/more/plugins'])

Step 3:
with plugin_source:
from yourapplication.plugins import my_plugin
my_plugin.do_something_cool()