python auto load sub module class.

__init__.py

from inspect import isclass
from pkgutil import iter_modules
from pathlib import Path
from importlib import import_module


REF = {}     
# iterate through the modules in the current package
package_dir = str(Path(__file__).resolve().parent)

def load_class(package_dir, import_path):
    for (_, module_name, ispkg) in iter_modules([package_dir]):
        if ispkg:
            import_path  = f'{import_path}.{module_name}'
            package_dir = f'{package_dir}/{module_name}'
            load_class(package_dir, import_path)
        else:
            # import the module and iterate through its attributes
            module = import_module(f"{import_path}.{module_name}")
            for attribute_name in dir(module):
                attribute = getattr(module, attribute_name)
                if isclass(attribute):            
                # Add the class to this package's variables
                    REF[attribute_name] = attribute

load_class(package_dir, __name__)