Import module from path

impfrom.py

import sys
import importlib.abc


# =====
def setup(*args, **kwargs):
    finder = _Finder(*args, **kwargs)
    sys.meta_path = [finder] + sys.meta_path
    return finder

def remove(finder):
    sys.meta_path.remove(finder)


# =====
class _Finder(importlib.abc.Finder):
    def __init__(self, root_name, get_path):
        assert callable(get_path), "get_path() must be a callable"
        self._root_name = root_name
        self._get_path = get_path

    def find_module(self, fullname, path=None):
        if fullname.split(".")[0] == self._root_name:
            if sys.version_info[:2] == (3, 2):  # PyPy/Python 3.2 hacks
                import importlib._bootstrap  # pylint: disable=W0621
                finder = importlib._bootstrap._file_path_hook(self._get_path())  # pylint: disable=W0212
                return finder.find_module(fullname)

            elif sys.version_info[:2] == (3, 4):  # Python 3.4
                import importlib.machinery
                finder = importlib.machinery.PathFinder
                return finder.find_module(fullname, [self._get_path()])

            else:
                RuntimeError("No importlib hacks for your Python: {}".format(sys.version_info))
        return None

Test:

# pylint: disable=R0904


import sys
import os
import unittest
import tempfile
import shutil
import contextlib

import impfrom


# =====
@contextlib.contextmanager
def _new_module(name):
    path = tempfile.mkdtemp(prefix="/tmp/")
    finder = impfrom.setup(name, lambda: path)
    yield (path, finder)
    impfrom.remove(finder)
    try:
        del sys.modules[name]
    except KeyError:
        pass
    shutil.rmtree(path)


# =====
class TestImpFrom(unittest.TestCase):
    def test_setup_remove(self):
        with _new_module("test_setup_remove") as (_, finder):
            self.assertTrue(finder in sys.meta_path)

    def test_import_module(self):
        with _new_module("test_import_module") as (path, _):
            with open(os.path.join(path, "test_import_module.py"), "w") as module_file:
                module_file.write("VAR1 = 1")
            import test_import_module  # pylint: disable=F0401
            self.assertEqual(test_import_module.VAR1, 1)

    def test_import_var_from_module(self):
        with _new_module("test_import_var_from_module") as (path, _):
            with open(os.path.join(path, "test_import_var_from_module.py"), "w") as module_file:
                module_file.write("VAR2 = 2")
            from test_import_var_from_module import VAR2  # pylint: disable=F0401
            self.assertEqual(VAR2, 2)