| **************************** |
| What's New In Python 3.9 |
| **************************** |
| |
| :Release: |release| |
| :Date: |today| |
| |
| .. Rules for maintenance: |
| |
| * Anyone can add text to this document. Do not spend very much time |
| on the wording of your changes, because your text will probably |
| get rewritten to some degree. |
| |
| * The maintainer will go through Misc/NEWS periodically and add |
| changes; it's therefore more important to add your changes to |
| Misc/NEWS than to this file. |
| |
| * This is not a complete list of every single change; completeness |
| is the purpose of Misc/NEWS. Some changes I consider too small |
| or esoteric to include. If such a change is added to the text, |
| I'll just remove it. (This is another reason you shouldn't spend |
| too much time on writing your addition.) |
| |
| * If you want to draw your new text to the attention of the |
| maintainer, add 'XXX' to the beginning of the paragraph or |
| section. |
| |
| * It's OK to just add a fragmentary note about a change. For |
| example: "XXX Describe the transmogrify() function added to the |
| socket module." The maintainer will research the change and |
| write the necessary text. |
| |
| * You can comment out your additions if you like, but it's not |
| necessary (especially when a final release is some months away). |
| |
| * Credit the author of a patch or bugfix. Just the name is |
| sufficient; the e-mail address isn't necessary. |
| |
| * It's helpful to add the bug/patch number as a comment: |
| |
| XXX Describe the transmogrify() function added to the socket |
| module. |
| (Contributed by P.Y. Developer in :issue:`12345`.) |
| |
| This saves the maintainer the effort of going through the Mercurial log |
| when researching a change. |
| |
| This article explains the new features in Python 3.9, compared to 3.8. |
| |
| For full details, see the :source:`Misc/NEWS` file. |
| |
| .. note:: |
| |
| Prerelease users should be aware that this document is currently in draft |
| form. It will be updated substantially as Python 3.9 moves towards release, |
| so it's worth checking back even after reading earlier versions. |
| |
| |
| Summary -- Release highlights |
| ============================= |
| |
| .. This section singles out the most important changes in Python 3.9. |
| Brevity is key. |
| |
| |
| .. PEP-sized items next. |
| |
| |
| |
| New Features |
| ============ |
| |
| |
| |
| Other Language Changes |
| ====================== |
| |
| |
| |
| New Modules |
| =========== |
| |
| * None yet. |
| |
| |
| Improved Modules |
| ================ |
| |
| threading |
| --------- |
| |
| In a subinterpreter, spawning a daemon thread now raises an exception. Daemon |
| threads were never supported in subinterpreters. Previously, the subinterpreter |
| finalization crashed with a Pyton fatal error if a daemon thread was still |
| running. |
| |
| |
| Optimizations |
| ============= |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| * Add a new public :c:func:`PyObject_CallNoArgs` function to the C API: |
| call a callable Python object without any arguments. It is the most efficient |
| way to call a callable Python object without any argument. |
| (Contributed by Victor Stinner in :issue:`37194`.) |
| |
| |
| |
| Deprecated |
| ========== |
| |
| * Currently :func:`math.factorial` accepts :class:`float` instances with |
| non-negative integer values (like ``5.0``). It raises a :exc:`ValueError` |
| for non-integral and negative floats. It is deprecated now. In future |
| Python versions it will raise a :exc:`TypeError` for all floats. |
| (Contributed by Serhiy Storchaka in :issue:`37315`.) |
| |
| |
| Removed |
| ======= |
| |
| * The C function ``PyImport_Cleanup()`` has been removed. It was documented as: |
| "Empty the module table. For internal use only." |
| (Contributed by Victor Stinner in :issue:`36710`.) |
| |
| * ``_dummy_thread`` and ``dummy_threading`` modules have been removed. These |
| modules were deprecated since Python 3.7 which requires threading support. |
| (Contributed by Victor Stinner in :issue:`37312`.) |
| |
| * ``aifc.openfp()`` alias to ``aifc.open()``, ``sunau.openfp()`` alias to |
| ``sunau.open()``, and ``wave.openfp()`` alias to ``wave.open()`` have been |
| removed. They were deprecated since Python 3.7. |
| (Contributed by Victor Stinner in :issue:`37320`.) |
| |
| |
| Porting to Python 3.9 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes |
| that may require changes to your code. |
| |
| |