Script to find and load classes from a specific directory

findmodules.py

import os
import inspect
import logging
from importlib.machinery import SourceFileLoader
import pkg_resources

logger = logging.getLogger(__name__)

# Search in "project/modules/"
SEARCH_PATHS = [pkg_resources.resource_filename("project", "modules")]

def search(base):
    """
    Search subclasses of class 'base' and return a list.
    """
    class_list = set()
    class_list_modules = set()  # for preventing module reload
    for path in SEARCH_PATHS:
        logger.debug('Entering path \'{}\''.format(path))
        for root, d, files in os.walk(path):
            # search for files with .py extension
            candidates = [fname for fname in files if fname.endswith('.py') and
                          not fname.startswith('__')]
            classes = []
            for c in candidates:
                # get filename
                modname = os.path.splitext(c)[0]
                try:
                    if modname in class_list_modules:
                        # module already loaded
                        continue

                    # load class into current Python env
                    module = SourceFileLoader(
                        modname,
                        os.path.join(root, c)).load_module()

                    # add loaded module to set
                    class_list_modules.add(modname)
                    logger.debug('Loaded module \'{}\''.format(modname))
                except (SystemError, ImportError,
                        NotImplementedError, SyntaxError) as e:
                    logger.debug(e)
                    logger.warn(f'Module could not be loaded: {modname}')
                    continue

                # enumerate classes found in module
                for cls in dir(module):
                    # for every class, get the actual "class" object" for checks
                    cls = getattr(module, cls)

                    # if class is a class and is part of the module 
                    # and is a subclass of argument base (but not the base itself)
                    if (inspect.isclass(cls) and
                            inspect.getmodule(cls) == module and
                            issubclass(cls, base) and
                            cls != base):

                        logger.info('Class found in {f}'.format(f=module))
                        # found
                        classes.append(cls)
            class_list.update(classes)

    logger.debug('Imported modules: {}'.format(str(class_list_modules)))
    logger.debug('Returned class list: {}'.format(str(class_list)))
    return list(class_list)