How to find all child modules in Python?

Question

While it is fairly trivial in Python to import a \"child\" module into another module and list its attributes, it becomes slightly more difficult when you want to import all

Answer 1

When I was a kind and just beginning programming in Python I've written this for my modular IRC bot:

    # Load plugins

    _plugins = []

    def ifName(name):
        try:
            return re.match('([^_.].+)\.[^.]+', a).group(1)
        except:
            return None

    def isValidPlugin(obj):
        from common.base import PluginBase
        try:
            if obj.__base__ == PluginBase:
                return True
            else:
                return False
        except:
            return False

    plugin_names = set(ifilter(lambda a: a!=None, [ifName(a) for a in os.listdir(os.path.join(os.getcwd(), 'plugins'))]))
    for plugin_name in plugin_names:
        try:
            plugin = __import__('plugins.'+plugin_name, fromlist=['plugins'])
            valid_plugins = filter(lambda a: isValidPlugin(a), [plugin.__getattribute__(a) for a in dir(plugin)])
            _plugins.extend(valid_plugins)
        except Exception, e:
            logger.exception('Error loading plugin %s', plugin_name)

    # Run plugins

    _plugins = [klass() for klass in _plugins]

It's not secure or "right" way, but maybe it we'll be useful nevertheless. It's very old code so please don't beat me.