plug-in loading example; https://github.com/lemon24/reader/issues/80

exampleplugin.py

def example():
    print('Example!')

loadplugin.py

import pkg_resources
import configparser


class PluginConfigParser(configparser.ConfigParser):

    optionxform = staticmethod(str)

    def __init__(self):
        super().__init__(
            allow_no_value=True,
            delimiters=('=', ),
            comment_prefixes=('#', ),
            inline_comment_prefixes=('#', ),
        )


def write_config_with_available_entry_points(file, groups):
    import_name = lambda ep: "{ep.module_name}:{ep.attrs[0]}".format(ep=ep)

    config = PluginConfigParser()
    for group in groups:
        entry_points = sorted(pkg_resources.iter_entry_points(group), key=import_name)
        config.add_section(group)
        for ep in entry_points:
            comment = ' # {ep.name} from {ep.dist.project_name}'.format(ep=ep)
            config[group][import_name(ep) + comment] = None

    config.write(file)


def import_string(import_name):
    ep = pkg_resources.EntryPoint.parse('none = ' + import_name)
    return ep.load(require=False)


def load_entry_points_from_file(file):
    config = PluginConfigParser()
    config.read_file(file)
    rv = {}
    for section in config.sections():
        rv[section] = []
        for ep in config[section]:
            rv.setdefault(section, []).append(import_string(ep))
    return rv



if __name__ == '__main__':
    import io

    file = io.StringIO()
    write_config_with_available_entry_points(file, [
        'reader.plugins.examples',
        'reader.plugins.otherexamples'
    ])

    print(file.getvalue())

    file.seek(0)
    entry_points = load_entry_points_from_file(file)

    for group, entry_points in sorted(entry_points.items()):
        for ep in entry_points:
            print('running', ep, 'from group', group)
            ep()

setup.py

from setuptools import setup

setup(
    name='ExamplePlugin',
    version='1.0',
    author='lemon24',
    url='https://github.com/lemon24/reader',
    py_modules=['exampleplugin'],
    entry_points={
        'reader.plugins.examples': ['example_name=exampleplugin:example'],
    },
    description="",
)

~output.txt

$ pip install -e .
Obtaining file:///home/lemon/code/reader/_plugins
Installing collected packages: ExamplePlugin
  Found existing installation: ExamplePlugin 1.0
    Uninstalling ExamplePlugin-1.0:
      Successfully uninstalled ExamplePlugin-1.0
  Running setup.py develop for ExamplePlugin
Successfully installed ExamplePlugin
$ python loadplugin.py 
[reader.plugins.examples]
exampleplugin:example # example_name from ExamplePlugin

[reader.plugins.otherexamples]


running <function example at 0x7f9cfc78b2f0> from group reader.plugins.examples
Example!
$