通过子类的方式实现插件

README

Plugin architecture based on "sub-class discovery method" described in a talk
by Dr. André Roberge. The talk is called "Plugins and monkeypatching:
increasing flexibility, dealing with inflexibility".

Here's the talk recorded at PyCon 2009 in Chicago:
http://us.pycon.org/2009/conference/schedule/event/47/

Plugin writer HOWTO:
1. subclass "Base"
2. implement sayHi()
3. place your plugin (the .py file) in this directory
4. run main.py

Note: written using python 2.6.5 on Ubuntu 10.04

See also:
* http://washort.twistedmatrix.com/2011/01/introducing-exocet.html / https://launchpad.net/exocet (recommended by dash/Allen Short in #python)
* http://stackoverflow.com/questions/932069/building-a-minimal-plugin-architecture-in-python
  * especially http://stackoverflow.com/questions/932069/building-a-minimal-plugin-architecture-in-python/933245#933245
* http://yapsy.sf.net/

base.py

class Base(object):
    pass

main.py

#!/usr/bin/python -tt

from base import Base
import os

plugins = []

def init_plugins():
    plugin_files = [x[:-3] for x in os.listdir('.') if x.endswith('.py')]
    for plugin in plugin_files:
        dummy = __import__(plugin)
    for plugin in Base.__subclasses__():
        plugins.append(plugin)

def run_plugins():
    for plugin in plugins:
        x = plugin()
        x.sayHi()

if __name__ == '__main__':
    init_plugins()
    run_plugins()

plugin_a.py

from base import Base

class A(Base):
    def sayHi(this):
        print "Hi, this is class A!"

plugin_b.py

from base import Base

class B(Base):
    def sayHi(this):
        print "Hi, this is class B!"