PEP 489: Multi-phase extension module initialization

Known limitations of the current implementation:

- documentation changes are incomplete
- there's a reference leak I haven't tracked down yet

The leak is most visible by running:

  ./python -m test -R3:3 test_importlib

However, you can also see it by running:

  ./python -X showrefcount

Importing the array or _testmultiphase modules, and
then deleting them from both sys.modules and the local
namespace shows significant increases in the total
number of active references each cycle. By contrast,
with _testcapi (which continues to use single-phase
initialisation) the global refcounts stabilise after
a couple of cycles.

1 files changed, 17 insertions, 2 deletions

diff --git a/Doc/whatsnew/3.5.rst b/Doc/whatsnew/3.5.rst
index c0f9346..75bc7fb 100644
--- a/Doc/whatsnew/3.5.rst
+++ b/Doc/whatsnew/3.5.rst
@@ -93,6 +93,7 @@ Implementation improvements:
   (:issue:`19977`).
 
 * :pep:`488`, the elimination of ``.pyo`` files.
+* :pep:`489`, multi-phase initialization of extension modules.
 
 Significantly Improved Library Modules:
 
@@ -265,6 +266,21 @@ updated API to help with this change.
    :pep:`488` -- Elimination of PYO files
 
 
+PEP 489: Multi-phase extension module initialization
+----------------------------------------------------
+
+:pep:`489` updates extension module initialization to take advantage of the
+two step module loading mechanism introduced by :pep:`451` in Python 3.4.
+
+This change brings the import semantics of extension modules that opt-in to
+using the new mechanism much closer to those of Python source and bytecode
+modules, including the ability to any valid identifier as a module name,
+rather than being restricted to ASCII.
+
+.. seealso::
+
+   :pep:`488` -- Multi-phase extension module initialization
+
 Other Language Changes
 ======================
 
@@ -667,7 +683,7 @@ time
 tkinter
 -------
 
-* The :module:`tkinter._fix` module used for setting up the Tcl/Tk environment
+* The :mod:`tkinter._fix` module used for setting up the Tcl/Tk environment
   on Windows has been replaced by a private function in the :module:`_tkinter`
   module which makes no permanent changes to environment variables.
   (Contributed by Zachary Ware in :issue:`20035`.)
@@ -1012,7 +1028,6 @@ Changes in the Python API
   program depends on patching the module level variable to capture the debug
   output, you will need to update it to capture sys.stderr instead.
 
-
 Changes in the C API
 --------------------