.. _python_37:
Python 3.7
==========
New Features:
.. table::
:widths: 20 60 20
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| **Feature** | **Status** |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 538 `_ | Coercing the legacy C locale to a UTF-8 based | |
| | locale | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 539 `_ | A New C-API for Thread-Local Storage in CPython | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 540 `_ | UTF-8 mode | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 552 `_ | Deterministic pyc | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 553 `_ | Built-in ``breakpoint()`` | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 557 `_ | Data Classes | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 560 `_ | Core support for typing module and generic types | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 562 `_ | Module ``__getattr__`` and ``__dir__`` | Partial |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 563 `_ | Postponed Evaluation of Annotations | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 564 `_ | Time functions with nanosecond resolution | Partial [#ftimenanosec]_ |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 565 `_ | Show DeprecationWarning in ``__main__`` | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
| `PEP 567 `_ | Context Variables | |
+--------------------------------------------------------+--------------------------------------------------+--------------------------------------+
Other Language Changes:
.. table::
:widths: 90 10
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``async`` and ``await`` are now reserved keywords | Complete |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``dict`` objects must preserve insertion-order | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| More than 255 arguments can now be passed to a function; a function can now have more than 255 parameters | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``bytes.fromhex()`` and ``bytearray.fromhex()`` now ignore all ASCII whitespace, not only spaces | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``str``, ``bytes``, and ``bytearray`` gained support for the new ``isascii()`` method, which can be used to | |
| test if a string or bytes contain only the ASCII characters | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``ImportError`` now displays module name and module ``__file__`` path when ``from ... import ...`` fails | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| Circular imports involving absolute imports with binding a submodule to a name are now supported | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| ``object.__format__(x, '')`` is now equivalent to ``str(x)`` rather than ``format(str(self), '')`` | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| In order to better support dynamic creation of stack traces, ``types.TracebackType`` can now be | |
| instantiated from Python code, and the ``tb_next`` attribute on tracebacks is now writable | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| When using the ``-m`` switch, ``sys.path[0]`` is now eagerly expanded to the full starting directory path, | |
| rather than being left as the empty directory (which allows imports from the current working directory | |
| at the time when an import occurs) | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
| The new ``-X importtime`` option or the ``PYTHONPROFILEIMPORTTIME`` environment variable can be used to | |
| show the timing of each module import | |
+-----------------------------------------------------------------------------------------------------------------+----------------+
Changes to built-in modules:
.. table::
:widths: 90 10
+------------------------------------------------------------------------------------------------------------+----------------+
| `asyncio `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| Too many to list | |
+------------------------------------------------------------------------------------------------------------+----------------+
| `gc `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| New features include *gc.freeze()*, *gc.unfreeze()*, *gc-get_freeze_count* | |
+------------------------------------------------------------------------------------------------------------+----------------+
| `math `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| math.remainder() added to implement IEEE 754-style remainder | |
+------------------------------------------------------------------------------------------------------------+----------------+
| `re `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| A number of tidy up features including better support for splitting on empty strings and copy support for | |
| compiled expressions and match objects | |
+------------------------------------------------------------------------------------------------------------+----------------+
| `sys `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| sys.breakpointhook() added. sys.get(/set)_coroutine_origin_tracking_depth() added | |
+------------------------------------------------------------------------------------------------------------+----------------+
| `time `_ | |
+------------------------------------------------------------------------------------------------------------+----------------+
| Mostly updates to support nanosecond resolution in PEP564, see above | |
+------------------------------------------------------------------------------------------------------------+----------------+
.. rubric:: Notes
.. [#ftimenanosec] Only :func:`time.time_ns` is implemented.