gh-104212: Add importlib.util.load_source() function

Author: vstinner

Doc/library/importlib.rst

@@ -1240,6 +1240,13 @@ an :term:`importer`.
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
 
+.. function:: load_source(module_name, filename)
+
+   Load a module from a filename: execute the module and add it to
+   :data:`sys.modules`.
+
+   .. versionadded:: 3.12
+
 .. function:: source_hash(source_bytes)
 
    Return the hash of *source_bytes* as bytes. A hash-based ``.pyc`` file embeds

Doc/whatsnew/3.12.rst

@@ -570,6 +570,12 @@ fractions
 * Objects of type :class:`fractions.Fraction` now support float-style
   formatting. (Contributed by Mark Dickinson in :gh:`100161`.)
 
+importlib
+---------
+
+* Add :func:`importlib.util.load_source` to load a module from a filename.
+  (Contributed by Victor Stinner in :gh:`104212`.)
+
 inspect
 -------
 
@@ -1371,6 +1377,9 @@ Removed
 
   * Replace ``imp.new_module(name)`` with ``types.ModuleType(name)``.
 
+  * Replace ``imp.load_source(module_name, filename)``
+    with ``importlib.util.load_source(module_name, filename)``.
+
 * Removed the ``suspicious`` rule from the documentation Makefile, and
   removed ``Doc/tools/rstlint.py``, both in favor of `sphinx-lint
   <https://github.com/sphinx-contrib/sphinx-lint>`_.

Lib/importlib/util.py

@@ -10,6 +10,7 @@
 from ._bootstrap_external import decode_source
 from ._bootstrap_external import source_from_cache
 from ._bootstrap_external import spec_from_file_location
+from ._bootstrap_external import SourceFileLoader
 
 import _imp
 import sys
@@ -246,3 +247,13 @@ def exec_module(self, module):
         loader_state['__class__'] = module.__class__
         module.__spec__.loader_state = loader_state
         module.__class__ = _LazyModule
+
+
+def load_source(module_name, filename):
+    """Load a module from a filename."""
+    loader = SourceFileLoader(module_name, filename)
+    module = types.ModuleType(loader.name)
+    module.__file__ = filename
+    sys.modules[module.__name__] = module
+    loader.exec_module(module)
+    return module

Lib/test/test_importlib/test_util.py

@@ -1,3 +1,4 @@
+from test.test_importlib import fixtures
 from test.test_importlib import util
 
 abc = util.import_importlib('importlib.abc')
@@ -12,6 +13,7 @@
 import string
 import sys
 from test import support
+from test.support import import_helper, os_helper
 import textwrap
 import types
 import unittest
@@ -758,5 +760,28 @@ def test_complete_multi_phase_init_module(self):
             self.run_with_own_gil(script)
 
 
+class LoadSourceTests(unittest.TestCase):
+    def test_load_source(self):
+        modname = 'test_load_source_mod'
+        filename = 'load_source_filename'
+
+        self.assertNotIn(modname, sys.modules)
+        self.addCleanup(import_helper.unload, modname)
+
+        # Use a temporary directory to remove __pycache__/ subdirectory
+        with fixtures.tempdir_as_cwd():
+            with open(filename, "w", encoding="utf8") as fp:
+                print("attr = 'load_source_attr'", file=fp)
+
+            mod = importlib.util.load_source(modname, filename)
+
+        self.assertIsInstance(mod, types.ModuleType)
+        self.assertEqual(mod.__name__, modname)
+        self.assertEqual(mod.__file__, filename)
+        self.assertIn(modname, sys.modules)
+        self.assertIs(sys.modules[modname], mod)
+        self.assertEqual(mod.attr, 'load_source_attr')
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2023-06-14-00-54-11.gh-issue-104212.4IJaKp.rst

@@ -0,0 +1,2 @@
+Add :func:`importlib.util.load_source` to load a module from a filename.
+Patch by Victor Stinner.