This code snippet defines a function import_submodules that imports all submodules of a given module recursively, including subpackages.

autoimport.py

from types import ModuleType


def import_submodules(module: ModuleType) -> None:
    """
    Import all submodules of a module, recursively, including subpackages.
    :param module: module (package) to import submodules of
    """
    import importlib
    import pkgutil

    path = getattr(module, "__path__", [])
    if path:
        for _loader, name, is_pkg in pkgutil.iter_modules(path):
            full_name = module.__name__ + "." + name
            print("Importing", full_name)
            submodule = importlib.import_module(full_name)
            if is_pkg:
                import_submodules(submodule)


if __name__ == "__main__":
    import_submodules(__import__("a"))

If using pyinstaller, do not forget to add --collect-submodules MODULENAME so pyinstaller will not forget to add the submodules in the executable.