bpo-32946: Speed up "from ... import ..." from non-packages. (GH-5873)

Lib/importlib/_bootstrap.py

@@ -1016,7 +1016,6 @@ def _handle_fromlist(module, fromlist, import_, *, recursive=False):
     """
     # The hell that is fromlist ...
     # If a package was imported, try to import stuff from fromlist.
-    if hasattr(module, '__path__'):
     for x in fromlist:
         if not isinstance(x, str):
             if recursive:
@@ -1102,8 +1101,10 @@ def __import__(name, globals=None, locals=None, fromlist=(), level=0):
             # Slice end needs to be positive to alleviate need to special-case
             # when ``'.' not in name``.
             return sys.modules[module.__name__[:len(module.__name__)-cut_off]]
-    else:
+    elif hasattr(module, '__path__'):
         return _handle_fromlist(module, fromlist, _gcd_import)
+    else:
+        return module
 
 
 def _builtin_from_name(name):

Misc/NEWS.d/next/Core and Builtins/2018-02-25-10-52-40.bpo-32946.Lo09rG.rst

+Importing names from already imported module with "from ... import ..." is
+now 30% faster if the module is not a package.

Python/import.c

@@ -1800,10 +1800,21 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
         }
     }
     else {
-        final_mod = _PyObject_CallMethodIdObjArgs(interp->importlib,
-                                                  &PyId__handle_fromlist, mod,
-                                                  fromlist, interp->import_func,
-                                                  NULL);
+        _Py_IDENTIFIER(__path__);
+        PyObject *path;
+        if (_PyObject_LookupAttrId(mod, &PyId___path__, &path) < 0) {
+            goto error;
+        }
+        if (path) {
+            Py_DECREF(path);
+            final_mod = _PyObject_CallMethodIdObjArgs(
+                        interp->importlib, &PyId__handle_fromlist,
+                        mod, fromlist, interp->import_func, NULL);
+        }
+        else {
+            final_mod = mod;
+            Py_INCREF(mod);
+        }
     }
 
   error: