custom Python module importer

app.py

from hook import register_import_hook


register_import_hook()

try:
    import test_foo
    print("✓ imported", test_foo.TEST_NAME, test_foo.TEST)
except Exception as err:
    print("✗ import failed:", err)

try:
    import test_bar
    print("✓ imported", test_bar.TEST_NAME, test_bar.TEST)
except Exception as err:
    print("✗ import failed:", err)

hook.py

import sys


class CustomImporter:

    PATH_TRIGGER = "test_"

    def __init__(self, path_entry):
        print("~~ INIT", path_entry)
        return

    def find_module(self, fullname, path=None):
        print("~~ FIND", fullname, path)

        mod = default_import(fullname, path) # TODO
        mod.TEST = True

        return mod


def register_import_hook():
    sys.path_hooks.append(CustomImporter)
    sys.path.insert(0, CustomImporter.PATH_TRIGGER)

test_bar.py

TEST_NAME = "BAR"
print("TEST", TEST_NAME)

test_foo.py

TEST_NAME = "FOO"
print("TEST", TEST_NAME)