| **************************** |
| What's New In Python 3.3 |
| **************************** |
| |
| .. 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 3.3, compared to 3.2. |
| Python 3.3 was released on September 29, 2012. For full details, |
| see the `changelog <http://docs.python.org/3.3/whatsnew/changelog.html>`_. |
| |
| .. seealso:: |
| |
| :pep:`398` - Python 3.3 Release Schedule |
| |
| |
| Summary -- Release highlights |
| ============================= |
| |
| .. This section singles out the most important changes in Python 3.3. |
| Brevity is key. |
| |
| New syntax features: |
| |
| * New ``yield from`` expression for :ref:`generator delegation <pep-380>`. |
| * The ``u'unicode'`` syntax is accepted again for :class:`str` objects. |
| |
| New library modules: |
| |
| * :mod:`faulthandler` (helps debugging low-level crashes) |
| * :mod:`ipaddress` (high-level objects representing IP addresses and masks) |
| * :mod:`lzma` (compress data using the XZ / LZMA algorithm) |
| * :mod:`unittest.mock` (replace parts of your system under test with mock objects) |
| * :mod:`venv` (Python :ref:`virtual environments <pep-405>`, as in the |
| popular ``virtualenv`` package) |
| |
| New built-in features: |
| |
| * Reworked :ref:`I/O exception hierarchy <pep-3151>`. |
| |
| Implementation improvements: |
| |
| * Rewritten :ref:`import machinery <importlib>` based on :mod:`importlib`. |
| * More compact :ref:`unicode strings <pep-393>`. |
| * More compact :ref:`attribute dictionaries <pep-412>`. |
| |
| Significantly Improved Library Modules: |
| |
| * C Accelerator for the :ref:`decimal <new-decimal>` module. |
| * Better unicode handling in the :ref:`email <new-email>` module |
| (:term:`provisional <provisional package>`). |
| |
| Security improvements: |
| |
| * Hash randomization is switched on by default. |
| |
| Please read on for a comprehensive list of user-facing changes. |
| |
| |
| .. _pep-405: |
| |
| PEP 405: Virtual Environments |
| ============================= |
| |
| Virtual environments help create separate Python setups while sharing a |
| system-wide base install, for ease of maintenance. Virtual environments |
| have their own set of private site packages (i.e. locally-installed |
| libraries), and are optionally segregated from the system-wide site |
| packages. Their concept and implementation are inspired by the popular |
| ``virtualenv`` third-party package, but benefit from tighter integration |
| with the interpreter core. |
| |
| This PEP adds the :mod:`venv` module for programmatic access, and the |
| :ref:`pyvenv <scripts-pyvenv>` script for command-line access and |
| administration. The Python interpreter checks for a ``pyvenv.cfg``, |
| file whose existence signals the base of a virtual environment's directory |
| tree. |
| |
| .. seealso:: |
| |
| :pep:`405` - Python Virtual Environments |
| PEP written by Carl Meyer; implementation by Carl Meyer and Vinay Sajip |
| |
| |
| PEP 420: Implicit Namespace Packages |
| ==================================== |
| |
| Native support for package directories that don't require ``__init__.py`` |
| marker files and can automatically span multiple path segments (inspired by |
| various third party approaches to namespace packages, as described in |
| :pep:`420`) |
| |
| .. seealso:: |
| |
| :pep:`420` - Implicit Namespace Packages |
| PEP written by Eric V. Smith; implementation by Eric V. Smith |
| and Barry Warsaw |
| |
| |
| .. _pep-3118-update: |
| |
| PEP 3118: New memoryview implementation and buffer protocol documentation |
| ========================================================================= |
| |
| The implementation of :pep:`3118` has been significantly improved. |
| |
| The new memoryview implementation comprehensively fixes all ownership and |
| lifetime issues of dynamically allocated fields in the Py_buffer struct |
| that led to multiple crash reports. Additionally, several functions that |
| crashed or returned incorrect results for non-contiguous or multi-dimensional |
| input have been fixed. |
| |
| The memoryview object now has a PEP-3118 compliant getbufferproc() |
| that checks the consumer's request type. Many new features have been |
| added, most of them work in full generality for non-contiguous arrays |
| and arrays with suboffsets. |
| |
| The documentation has been updated, clearly spelling out responsibilities |
| for both exporters and consumers. Buffer request flags are grouped into |
| basic and compound flags. The memory layout of non-contiguous and |
| multi-dimensional NumPy-style arrays is explained. |
| |
| Features |
| -------- |
| |
| * All native single character format specifiers in struct module syntax |
| (optionally prefixed with '@') are now supported. |
| |
| * With some restrictions, the cast() method allows changing of format and |
| shape of C-contiguous arrays. |
| |
| * Multi-dimensional list representations are supported for any array type. |
| |
| * Multi-dimensional comparisons are supported for any array type. |
| |
| * One-dimensional memoryviews of hashable (read-only) types with formats B, |
| b or c are now hashable. (Contributed by Antoine Pitrou in :issue:`13411`) |
| |
| * Arbitrary slicing of any 1-D arrays type is supported. For example, it |
| is now possible to reverse a memoryview in O(1) by using a negative step. |
| |
| API changes |
| ----------- |
| |
| * The maximum number of dimensions is officially limited to 64. |
| |
| * The representation of empty shape, strides and suboffsets is now |
| an empty tuple instead of None. |
| |
| * Accessing a memoryview element with format 'B' (unsigned bytes) |
| now returns an integer (in accordance with the struct module syntax). |
| For returning a bytes object the view must be cast to 'c' first. |
| |
| * memoryview comparisons now use the logical structure of the operands |
| and compare all array elements by value. All format strings in struct |
| module syntax are supported. Views with unrecognised format strings |
| are still permitted, but will always compare as unequal, regardless |
| of view contents. |
| |
| * For further changes see `Build and C API Changes`_ and `Porting C code`_. |
| |
| (Contributed by Stefan Krah in :issue:`10181`) |
| |
| .. seealso:: |
| |
| :pep:`3118` - Revising the Buffer Protocol |
| |
| |
| .. _pep-393: |
| |
| PEP 393: Flexible String Representation |
| ======================================= |
| |
| The Unicode string type is changed to support multiple internal |
| representations, depending on the character with the largest Unicode ordinal |
| (1, 2, or 4 bytes) in the represented string. This allows a space-efficient |
| representation in common cases, but gives access to full UCS-4 on all |
| systems. For compatibility with existing APIs, several representations may |
| exist in parallel; over time, this compatibility should be phased out. |
| |
| On the Python side, there should be no downside to this change. |
| |
| On the C API side, PEP 393 is fully backward compatible. The legacy API |
| should remain available at least five years. Applications using the legacy |
| API will not fully benefit of the memory reduction, or - worse - may use |
| a bit more memory, because Python may have to maintain two versions of each |
| string (in the legacy format and in the new efficient storage). |
| |
| Functionality |
| ------------- |
| |
| Changes introduced by :pep:`393` are the following: |
| |
| * Python now always supports the full range of Unicode codepoints, including |
| non-BMP ones (i.e. from ``U+0000`` to ``U+10FFFF``). The distinction between |
| narrow and wide builds no longer exists and Python now behaves like a wide |
| build, even under Windows. |
| |
| * With the death of narrow builds, the problems specific to narrow builds have |
| also been fixed, for example: |
| |
| * :func:`len` now always returns 1 for non-BMP characters, |
| so ``len('\U0010FFFF') == 1``; |
| |
| * surrogate pairs are not recombined in string literals, |
| so ``'\uDBFF\uDFFF' != '\U0010FFFF'``; |
| |
| * indexing or slicing non-BMP characters returns the expected value, |
| so ``'\U0010FFFF'[0]`` now returns ``'\U0010FFFF'`` and not ``'\uDBFF'``; |
| |
| * all other functions in the standard library now correctly handle |
| non-BMP codepoints. |
| |
| * The value of :data:`sys.maxunicode` is now always ``1114111`` (``0x10FFFF`` |
| in hexadecimal). The :c:func:`PyUnicode_GetMax` function still returns |
| either ``0xFFFF`` or ``0x10FFFF`` for backward compatibility, and it should |
| not be used with the new Unicode API (see :issue:`13054`). |
| |
| * The :file:`./configure` flag ``--with-wide-unicode`` has been removed. |
| |
| Performance and resource usage |
| ------------------------------ |
| |
| The storage of Unicode strings now depends on the highest codepoint in the string: |
| |
| * pure ASCII and Latin1 strings (``U+0000-U+00FF``) use 1 byte per codepoint; |
| |
| * BMP strings (``U+0000-U+FFFF``) use 2 bytes per codepoint; |
| |
| * non-BMP strings (``U+10000-U+10FFFF``) use 4 bytes per codepoint. |
| |
| The net effect is that for most applications, memory usage of string |
| storage should decrease significantly - especially compared to former |
| wide unicode builds - as, in many cases, strings will be pure ASCII |
| even in international contexts (because many strings store non-human |
| language data, such as XML fragments, HTTP headers, JSON-encoded data, |
| etc.). We also hope that it will, for the same reasons, increase CPU |
| cache efficiency on non-trivial applications. The memory usage of |
| Python 3.3 is two to three times smaller than Python 3.2, and a little |
| bit better than Python 2.7, on a Django benchmark (see the PEP for |
| details). |
| |
| .. seealso:: |
| |
| :pep:`393` - Flexible String Representation |
| PEP written by Martin von Löwis; implementation by Torsten Becker |
| and Martin von Löwis. |
| |
| |
| .. _pep-397: |
| |
| PEP 397: Python Launcher for Windows |
| ==================================== |
| |
| The Python 3.3 Windows installer now includes a ``py`` launcher application |
| that can be used to launch Python applications in a version independent |
| fashion. |
| |
| This launcher is invoked implicitly when double-clicking ``*.py`` files. |
| If only a single Python version is installed on the system, that version |
| will be used to run the file. If multiple versions are installed, the most |
| recent version is used by default, but this can be overridden by including |
| a Unix-style "shebang line" in the Python script. |
| |
| The launcher can also be used explicitly from the command line as the ``py`` |
| application. Running ``py`` follows the same version selection rules as |
| implicitly launching scripts, but a more specific version can be selected |
| by passing appropriate arguments (such as ``-3`` to request Python 3 when |
| Python 2 is also installed, or ``-2.6`` to specifclly request an earlier |
| Python version when a more recent version is installed). |
| |
| In addition to the launcher, the Windows installer now includes an |
| option to add the newly installed Python to the system PATH (contributed |
| by Brian Curtin in :issue:`3561`). |
| |
| .. seealso:: |
| |
| :pep:`397` - Python Launcher for Windows |
| PEP written by Mark Hammond and Martin v. Löwis; implementation by |
| Vinay Sajip. |
| |
| Launcher documentation: :ref:`launcher` |
| |
| Installer PATH modification: :ref:`windows-path-mod` |
| |
| |
| .. _pep-3151: |
| |
| PEP 3151: Reworking the OS and IO exception hierarchy |
| ===================================================== |
| |
| The hierarchy of exceptions raised by operating system errors is now both |
| simplified and finer-grained. |
| |
| You don't have to worry anymore about choosing the appropriate exception |
| type between :exc:`OSError`, :exc:`IOError`, :exc:`EnvironmentError`, |
| :exc:`WindowsError`, :exc:`mmap.error`, :exc:`socket.error` or |
| :exc:`select.error`. All these exception types are now only one: |
| :exc:`OSError`. The other names are kept as aliases for compatibility |
| reasons. |
| |
| Also, it is now easier to catch a specific error condition. Instead of |
| inspecting the ``errno`` attribute (or ``args[0]``) for a particular |
| constant from the :mod:`errno` module, you can catch the adequate |
| :exc:`OSError` subclass. The available subclasses are the following: |
| |
| * :exc:`BlockingIOError` |
| * :exc:`ChildProcessError` |
| * :exc:`ConnectionError` |
| * :exc:`FileExistsError` |
| * :exc:`FileNotFoundError` |
| * :exc:`InterruptedError` |
| * :exc:`IsADirectoryError` |
| * :exc:`NotADirectoryError` |
| * :exc:`PermissionError` |
| * :exc:`ProcessLookupError` |
| * :exc:`TimeoutError` |
| |
| And the :exc:`ConnectionError` itself has finer-grained subclasses: |
| |
| * :exc:`BrokenPipeError` |
| * :exc:`ConnectionAbortedError` |
| * :exc:`ConnectionRefusedError` |
| * :exc:`ConnectionResetError` |
| |
| Thanks to the new exceptions, common usages of the :mod:`errno` can now be |
| avoided. For example, the following code written for Python 3.2:: |
| |
| from errno import ENOENT, EACCES, EPERM |
| |
| try: |
| with open("document.txt") as f: |
| content = f.read() |
| except IOError as err: |
| if err.errno == ENOENT: |
| print("document.txt file is missing") |
| elif err.errno in (EACCES, EPERM): |
| print("You are not allowed to read document.txt") |
| else: |
| raise |
| |
| can now be written without the :mod:`errno` import and without manual |
| inspection of exception attributes:: |
| |
| try: |
| with open("document.txt") as f: |
| content = f.read() |
| except FileNotFoundError: |
| print("document.txt file is missing") |
| except PermissionError: |
| print("You are not allowed to read document.txt") |
| |
| .. seealso:: |
| |
| :pep:`3151` - Reworking the OS and IO Exception Hierarchy |
| PEP written and implemented by Antoine Pitrou |
| |
| |
| .. index:: |
| single: yield; yield from (in What's New) |
| |
| .. _pep-380: |
| |
| PEP 380: Syntax for Delegating to a Subgenerator |
| ================================================ |
| |
| PEP 380 adds the ``yield from`` expression, allowing a :term:`generator` to |
| delegate |
| part of its operations to another generator. This allows a section of code |
| containing :keyword:`yield` to be factored out and placed in another generator. |
| Additionally, the subgenerator is allowed to return with a value, and the |
| value is made available to the delegating generator. |
| |
| While designed primarily for use in delegating to a subgenerator, the ``yield |
| from`` expression actually allows delegation to arbitrary subiterators. |
| |
| For simple iterators, ``yield from iterable`` is essentially just a shortened |
| form of ``for item in iterable: yield item``:: |
| |
| >>> def g(x): |
| ... yield from range(x, 0, -1) |
| ... yield from range(x) |
| ... |
| >>> list(g(5)) |
| [5, 4, 3, 2, 1, 0, 1, 2, 3, 4] |
| |
| However, unlike an ordinary loop, ``yield from`` allows subgenerators to |
| receive sent and thrown values directly from the calling scope, and |
| return a final value to the outer generator:: |
| |
| >>> def accumulate(): |
| ... tally = 0 |
| ... while 1: |
| ... next = yield |
| ... if next is None: |
| ... return tally |
| ... tally += next |
| ... |
| >>> def gather_tallies(tallies): |
| ... while 1: |
| ... tally = yield from accumulate() |
| ... tallies.append(tally) |
| ... |
| >>> tallies = [] |
| >>> acc = gather_tallies(tallies) |
| >>> next(acc) # Ensure the accumulator is ready to accept values |
| >>> for i in range(4): |
| ... acc.send(i) |
| ... |
| >>> acc.send(None) # Finish the first tally |
| >>> for i in range(5): |
| ... acc.send(i) |
| ... |
| >>> acc.send(None) # Finish the second tally |
| >>> tallies |
| [6, 10] |
| |
| The main principle driving this change is to allow even generators that are |
| designed to be used with the ``send`` and ``throw`` methods to be split into |
| multiple subgenerators as easily as a single large function can be split into |
| multiple subfunctions. |
| |
| .. seealso:: |
| |
| :pep:`380` - Syntax for Delegating to a Subgenerator |
| PEP written by Greg Ewing; implementation by Greg Ewing, integrated into |
| 3.3 by Renaud Blanch, Ryan Kelly and Nick Coghlan; documentation by |
| Zbigniew Jędrzejewski-Szmek and Nick Coghlan |
| |
| |
| PEP 409: Suppressing exception context |
| ====================================== |
| |
| PEP 409 introduces new syntax that allows the display of the chained |
| exception context to be disabled. This allows cleaner error messages in |
| applications that convert between exception types:: |
| |
| >>> class D: |
| ... def __init__(self, extra): |
| ... self._extra_attributes = extra |
| ... def __getattr__(self, attr): |
| ... try: |
| ... return self._extra_attributes[attr] |
| ... except KeyError: |
| ... raise AttributeError(attr) from None |
| ... |
| >>> D({}).x |
| Traceback (most recent call last): |
| File "<stdin>", line 1, in <module> |
| File "<stdin>", line 8, in __getattr__ |
| AttributeError: x |
| |
| Without the ``from None`` suffix to suppress the cause, the original |
| exception would be displayed by default:: |
| |
| >>> class C: |
| ... def __init__(self, extra): |
| ... self._extra_attributes = extra |
| ... def __getattr__(self, attr): |
| ... try: |
| ... return self._extra_attributes[attr] |
| ... except KeyError: |
| ... raise AttributeError(attr) |
| ... |
| >>> C({}).x |
| Traceback (most recent call last): |
| File "<stdin>", line 6, in __getattr__ |
| KeyError: 'x' |
| |
| During handling of the above exception, another exception occurred: |
| |
| Traceback (most recent call last): |
| File "<stdin>", line 1, in <module> |
| File "<stdin>", line 8, in __getattr__ |
| AttributeError: x |
| |
| No debugging capability is lost, as the original exception context remains |
| available if needed (for example, if an intervening library has incorrectly |
| suppressed valuable underlying details):: |
| |
| >>> try: |
| ... D({}).x |
| ... except AttributeError as exc: |
| ... print(repr(exc.__context__)) |
| ... |
| KeyError('x',) |
| |
| .. seealso:: |
| |
| :pep:`409` - Suppressing exception context |
| PEP written by Ethan Furman; implemented by Ethan Furman and Nick |
| Coghlan. |
| |
| |
| PEP 414: Explicit Unicode literals |
| ====================================== |
| |
| To ease the transition from Python 2 for Unicode aware Python applications |
| that make heavy use of Unicode literals, Python 3.3 once again supports the |
| "``u``" prefix for string literals. This prefix has no semantic significance |
| in Python 3, it is provided solely to reduce the number of purely mechanical |
| changes in migrating to Python 3, making it easier for developers to focus on |
| the more significant semantic changes (such as the stricter default |
| separation of binary and text data). |
| |
| .. seealso:: |
| |
| :pep:`414` - Explicit Unicode literals |
| PEP written by Armin Ronacher. |
| |
| |
| PEP 3155: Qualified name for classes and functions |
| ================================================== |
| |
| Functions and class objects have a new ``__qualname__`` attribute representing |
| the "path" from the module top-level to their definition. For global functions |
| and classes, this is the same as ``__name__``. For other functions and classes, |
| it provides better information about where they were actually defined, and |
| how they might be accessible from the global scope. |
| |
| Example with (non-bound) methods:: |
| |
| >>> class C: |
| ... def meth(self): |
| ... pass |
| >>> C.meth.__name__ |
| 'meth' |
| >>> C.meth.__qualname__ |
| 'C.meth' |
| |
| Example with nested classes:: |
| |
| >>> class C: |
| ... class D: |
| ... def meth(self): |
| ... pass |
| ... |
| >>> C.D.__name__ |
| 'D' |
| >>> C.D.__qualname__ |
| 'C.D' |
| >>> C.D.meth.__name__ |
| 'meth' |
| >>> C.D.meth.__qualname__ |
| 'C.D.meth' |
| |
| Example with nested functions:: |
| |
| >>> def outer(): |
| ... def inner(): |
| ... pass |
| ... return inner |
| ... |
| >>> outer().__name__ |
| 'inner' |
| >>> outer().__qualname__ |
| 'outer.<locals>.inner' |
| |
| The string representation of those objects is also changed to include the |
| new, more precise information:: |
| |
| >>> str(C.D) |
| "<class '__main__.C.D'>" |
| >>> str(C.D.meth) |
| '<function C.D.meth at 0x7f46b9fe31e0>' |
| |
| .. seealso:: |
| |
| :pep:`3155` - Qualified name for classes and functions |
| PEP written and implemented by Antoine Pitrou. |
| |
| |
| .. _pep-412: |
| |
| PEP 412: Key-Sharing Dictionary |
| =============================== |
| |
| Dictionaries used for the storage of objects' attributes are now able to |
| share part of their internal storage between each other (namely, the part |
| which stores the keys and their respective hashes). This reduces the memory |
| consumption of programs creating many instances of non-builtin types. |
| |
| .. seealso:: |
| |
| :pep:`412` - Key-Sharing Dictionary |
| PEP written and implemented by Mark Shannon. |
| |
| |
| PEP 362: Function Signature Object |
| ================================== |
| |
| A new function :func:`inspect.signature` makes introspection of python |
| callables easy and straightforward. A broad range of callables is supported: |
| python functions, decorated or not, classes, and :func:`functools.partial` |
| objects. New classes :class:`inspect.Signature`, :class:`inspect.Parameter` |
| and :class:`inspect.BoundArguments` hold information about the call signatures, |
| such as, annotations, default values, parameters kinds, and bound arguments, |
| which considerably simplifies writing decorators and any code that validates |
| or amends calling signatures or arguments. |
| |
| .. seealso:: |
| |
| :pep:`362`: - Function Signature Object |
| PEP written by Brett Cannon, Yury Selivanov, Larry Hastings, Jiwon Seo; |
| implemented by Yury Selivanov. |
| |
| |
| PEP 421: Adding sys.implementation |
| ================================== |
| |
| A new attribute on the :mod:`sys` module exposes details specific to the |
| implementation of the currently running interpreter. The initial set of |
| attributes on :attr:`sys.implementation` are ``name``, ``version``, |
| ``hexversion``, and ``cache_tag``. |
| |
| The intention of ``sys.implementation`` is to consolidate into one namespace |
| the implementation-specific data used by the standard library. This allows |
| different Python implementations to share a single standard library code base |
| much more easily. In its initial state, ``sys.implementation`` holds only a |
| small portion of the implementation-specific data. Over time that ratio will |
| shift in order to make the standard library more portable. |
| |
| One example of improved standard library portability is ``cache_tag``. As of |
| Python 3.3, ``sys.implementation.cache_tag`` is used by :mod:`importlib` to |
| support :pep:`3147` compliance. Any Python implementation that uses |
| ``importlib`` for its built-in import system may use ``cache_tag`` to control |
| the caching behavior for modules. |
| |
| SimpleNamespace |
| --------------- |
| |
| The implementation of ``sys.implementation`` also introduces a new type to |
| Python: :class:`types.SimpleNamespace`. In contrast to a mapping-based |
| namespace, like :class:`dict`, ``SimpleNamespace`` is attribute-based, like |
| :class:`object`. However, unlike ``object``, ``SimpleNamespace`` instances |
| are writable. This means that you can add, remove, and modify the namespace |
| through normal attribute access. |
| |
| .. seealso:: |
| |
| :pep:`421` - Adding sys.implementation |
| PEP written and implemented by Eric Snow. |
| |
| |
| .. _importlib: |
| |
| Using importlib as the Implementation of Import |
| =============================================== |
| :issue:`2377` - Replace __import__ w/ importlib.__import__ |
| :issue:`13959` - Re-implement parts of :mod:`imp` in pure Python |
| :issue:`14605` - Make import machinery explicit |
| :issue:`14646` - Require loaders set __loader__ and __package__ |
| |
| The :func:`__import__` function is now powered by :func:`importlib.__import__`. |
| This work leads to the completion of "phase 2" of :pep:`302`. There are |
| multiple benefits to this change. First, it has allowed for more of the |
| machinery powering import to be exposed instead of being implicit and hidden |
| within the C code. It also provides a single implementation for all Python VMs |
| supporting Python 3.3 to use, helping to end any VM-specific deviations in |
| import semantics. And finally it eases the maintenance of import, allowing for |
| future growth to occur. |
| |
| For the common user, there should be no visible change in semantics. For |
| those whose code currently manipulates import or calls import |
| programmatically, the code changes that might possibly be required are covered |
| in the `Porting Python code`_ section of this document. |
| |
| New APIs |
| -------- |
| One of the large benefits of this work is the exposure of what goes into |
| making the import statement work. That means the various importers that were |
| once implicit are now fully exposed as part of the :mod:`importlib` package. |
| |
| The abstract base classes defined in :mod:`importlib.abc` have been expanded |
| to properly delineate between :term:`meta path finders <meta path finder>` |
| and :term:`path entry finders <path entry finder>` by introducing |
| :class:`importlib.abc.MetaPathFinder` and |
| :class:`importlib.abc.PathEntryFinder`, respectively. The old ABC of |
| :class:`importlib.abc.Finder` is now only provided for backwards-compatibility |
| and does not enforce any method requirements. |
| |
| In terms of finders, :class:`importlib.machinery.FileFinder` exposes the |
| mechanism used to search for source and bytecode files of a module. Previously |
| this class was an implicit member of :attr:`sys.path_hooks`. |
| |
| For loaders, the new abstract base class :class:`importlib.abc.FileLoader` helps |
| write a loader that uses the file system as the storage mechanism for a module's |
| code. The loader for source files |
| (:class:`importlib.machinery.SourceFileLoader`), sourceless bytecode files |
| (:class:`importlib.machinery.SourcelessFileLoader`), and extension modules |
| (:class:`importlib.machinery.ExtensionFileLoader`) are now available for |
| direct use. |
| |
| :exc:`ImportError` now has ``name`` and ``path`` attributes which are set when |
| there is relevant data to provide. The message for failed imports will also |
| provide the full name of the module now instead of just the tail end of the |
| module's name. |
| |
| The :func:`importlib.invalidate_caches` function will now call the method with |
| the same name on all finders cached in :attr:`sys.path_importer_cache` to help |
| clean up any stored state as necessary. |
| |
| Visible Changes |
| --------------- |
| |
| For potential required changes to code, see the `Porting Python code`_ |
| section. |
| |
| Beyond the expanse of what :mod:`importlib` now exposes, there are other |
| visible changes to import. The biggest is that :attr:`sys.meta_path` and |
| :attr:`sys.path_hooks` now store all of the meta path finders and path entry |
| hooks used by import. Previously the finders were implicit and hidden within |
| the C code of import instead of being directly exposed. This means that one can |
| now easily remove or change the order of the various finders to fit one's needs. |
| |
| Another change is that all modules have a ``__loader__`` attribute, storing the |
| loader used to create the module. :pep:`302` has been updated to make this |
| attribute mandatory for loaders to implement, so in the future once 3rd-party |
| loaders have been updated people will be able to rely on the existence of the |
| attribute. Until such time, though, import is setting the module post-load. |
| |
| Loaders are also now expected to set the ``__package__`` attribute from |
| :pep:`366`. Once again, import itself is already setting this on all loaders |
| from :mod:`importlib` and import itself is setting the attribute post-load. |
| |
| ``None`` is now inserted into :attr:`sys.path_importer_cache` when no finder |
| can be found on :attr:`sys.path_hooks`. Since :class:`imp.NullImporter` is not |
| directly exposed on :attr:`sys.path_hooks` it could no longer be relied upon to |
| always be available to use as a value representing no finder found. |
| |
| All other changes relate to semantic changes which should be taken into |
| consideration when updating code for Python 3.3, and thus should be read about |
| in the `Porting Python code`_ section of this document. |
| |
| (Implementation by Brett Cannon) |
| |
| |
| Other Language Changes |
| ====================== |
| |
| Some smaller changes made to the core Python language are: |
| |
| * Added support for Unicode name aliases and named sequences. |
| Both :func:`unicodedata.lookup()` and ``'\N{...}'`` now resolve name aliases, |
| and :func:`unicodedata.lookup()` resolves named sequences too. |
| |
| (Contributed by Ezio Melotti in :issue:`12753`) |
| |
| * Unicode database updated to UCD version 6.1.0 |
| |
| * Equality comparisons on :func:`range` objects now return a result reflecting |
| the equality of the underlying sequences generated by those range objects. |
| (:issue:`13201`) |
| |
| * The ``count()``, ``find()``, ``rfind()``, ``index()`` and ``rindex()`` |
| methods of :class:`bytes` and :class:`bytearray` objects now accept an |
| integer between 0 and 255 as their first argument. |
| |
| (Contributed by Petri Lehtinen in :issue:`12170`) |
| |
| * The ``rjust()``, ``ljust()``, and ``center()`` methods of :class:`bytes` |
| and :class:`bytearray` now accept a :class:`bytearray` for the ``fill`` |
| argument. (Contributed by Petri Lehtinen in :issue:`12380`.) |
| |
| * New methods have been added to :class:`list` and :class:`bytearray`: |
| ``copy()`` and ``clear()`` (:issue:`10516`). Consequently, |
| :class:`~collections.abc.MutableSequence` now also defines a |
| :meth:`~collections.abc.MutableSequence.clear` method (:issue:`11388`). |
| |
| * Raw bytes literals can now be written ``rb"..."`` as well as ``br"..."``. |
| |
| (Contributed by Antoine Pitrou in :issue:`13748`.) |
| |
| * :meth:`dict.setdefault` now does only one lookup for the given key, making |
| it atomic when used with built-in types. |
| |
| (Contributed by Filip Gruszczyński in :issue:`13521`.) |
| |
| * The error messages produced when a function call does not match the function |
| signature have been significantly improved. |
| |
| (Contributed by Benjamin Peterson.) |
| |
| |
| A Finer-Grained Import Lock |
| =========================== |
| |
| Previous versions of CPython have always relied on a global import lock. |
| This led to unexpected annoyances, such as deadlocks when importing a module |
| would trigger code execution in a different thread as a side-effect. |
| Clumsy workarounds were sometimes employed, such as the |
| :c:func:`PyImport_ImportModuleNoBlock` C API function. |
| |
| In Python 3.3, importing a module takes a per-module lock. This correctly |
| serializes importation of a given module from multiple threads (preventing |
| the exposure of incompletely initialized modules), while eliminating the |
| aforementioned annoyances. |
| |
| (Contributed by Antoine Pitrou in :issue:`9260`.) |
| |
| |
| Builtin functions and types |
| =========================== |
| |
| * :func:`open` gets a new *opener* parameter: the underlying file descriptor |
| for the file object is then obtained by calling *opener* with (*file*, |
| *flags*). It can be used to use custom flags like :data:`os.O_CLOEXEC` for |
| example. The ``'x'`` mode was added: open for exclusive creation, failing if |
| the file already exists. |
| * :func:`print`: added the *flush* keyword argument. If the *flush* keyword |
| argument is true, the stream is forcibly flushed. |
| * :func:`hash`: hash randomization is enabled by default, see |
| :meth:`object.__hash__` and :envvar:`PYTHONHASHSEED`. |
| * The :class:`str` type gets a new :meth:`~str.casefold` method: return a |
| casefolded copy of the string, casefolded strings may be used for caseless |
| matching. For example, ``'ß'.casefold()`` returns ``'ss'``. |
| * The sequence documentation has been substantially rewritten to better |
| explain the binary/text sequence distinction and to provide specific |
| documentation sections for the individual builtin sequence types |
| (:issue:`4966`) |
| |
| |
| New Modules |
| =========== |
| |
| faulthandler |
| ------------ |
| |
| This new debug module :mod:`faulthandler` contains functions to dump Python tracebacks explicitly, |
| on a fault (a crash like a segmentation fault), after a timeout, or on a user |
| signal. Call :func:`faulthandler.enable` to install fault handlers for the |
| :const:`SIGSEGV`, :const:`SIGFPE`, :const:`SIGABRT`, :const:`SIGBUS`, and |
| :const:`SIGILL` signals. You can also enable them at startup by setting the |
| :envvar:`PYTHONFAULTHANDLER` environment variable or by using :option:`-X` |
| ``faulthandler`` command line option. |
| |
| Example of a segmentation fault on Linux: :: |
| |
| $ python -q -X faulthandler |
| >>> import ctypes |
| >>> ctypes.string_at(0) |
| Fatal Python error: Segmentation fault |
| |
| Current thread 0x00007fb899f39700: |
| File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at |
| File "<stdin>", line 1 in <module> |
| Segmentation fault |
| |
| |
| ipaddress |
| --------- |
| |
| The new :mod:`ipaddress` module provides tools for creating and manipulating |
| objects representing IPv4 and IPv6 addresses, networks and interfaces (i.e. |
| an IP address associated with a specific IP subnet). |
| |
| (Contributed by Google and Peter Moody in :pep:`3144`) |
| |
| lzma |
| ---- |
| |
| The newly-added :mod:`lzma` module provides data compression and decompression |
| using the LZMA algorithm, including support for the ``.xz`` and ``.lzma`` |
| file formats. |
| |
| (Contributed by Nadeem Vawda and Per Øyvind Karlsen in :issue:`6715`) |
| |
| |
| Improved Modules |
| ================ |
| |
| abc |
| --- |
| |
| Improved support for abstract base classes containing descriptors composed with |
| abstract methods. The recommended approach to declaring abstract descriptors is |
| now to provide :attr:`__isabstractmethod__` as a dynamically updated |
| property. The built-in descriptors have been updated accordingly. |
| |
| * :class:`abc.abstractproperty` has been deprecated, use :class:`property` |
| with :func:`abc.abstractmethod` instead. |
| * :class:`abc.abstractclassmethod` has been deprecated, use |
| :class:`classmethod` with :func:`abc.abstractmethod` instead. |
| * :class:`abc.abstractstaticmethod` has been deprecated, use |
| :class:`staticmethod` with :func:`abc.abstractmethod` instead. |
| |
| (Contributed by Darren Dale in :issue:`11610`) |
| |
| :meth:`abc.ABCMeta.register` now returns the registered subclass, which means |
| it can now be used as a class decorator (:issue:`10868`). |
| |
| |
| array |
| ----- |
| |
| The :mod:`array` module supports the :c:type:`long long` type using ``q`` and |
| ``Q`` type codes. |
| |
| (Contributed by Oren Tirosh and Hirokazu Yamamoto in :issue:`1172711`) |
| |
| |
| base64 |
| ------ |
| |
| ASCII-only Unicode strings are now accepted by the decoding functions of the |
| :mod:`base64` modern interface. For example, ``base64.b64decode('YWJj')`` |
| returns ``b'abc'``. (Contributed by Catalin Iacob in :issue:`13641`.) |
| |
| |
| binascii |
| -------- |
| |
| In addition to the binary objects they normally accept, the ``a2b_`` functions |
| now all also accept ASCII-only strings as input. (Contributed by Antoine |
| Pitrou in :issue:`13637`.) |
| |
| |
| bz2 |
| --- |
| |
| The :mod:`bz2` module has been rewritten from scratch. In the process, several |
| new features have been added: |
| |
| * New :func:`bz2.open` function: open a bzip2-compressed file in binary or |
| text mode. |
| |
| * :class:`bz2.BZ2File` can now read from and write to arbitrary file-like |
| objects, by means of its constructor's *fileobj* argument. |
| |
| (Contributed by Nadeem Vawda in :issue:`5863`) |
| |
| * :class:`bz2.BZ2File` and :func:`bz2.decompress` can now decompress |
| multi-stream inputs (such as those produced by the :program:`pbzip2` tool). |
| :class:`bz2.BZ2File` can now also be used to create this type of file, using |
| the ``'a'`` (append) mode. |
| |
| (Contributed by Nir Aides in :issue:`1625`) |
| |
| * :class:`bz2.BZ2File` now implements all of the :class:`io.BufferedIOBase` API, |
| except for the :meth:`detach` and :meth:`truncate` methods. |
| |
| |
| codecs |
| ------ |
| |
| The :mod:`~encodings.mbcs` codec has been rewritten to handle correctly |
| ``replace`` and ``ignore`` error handlers on all Windows versions. The |
| :mod:`~encodings.mbcs` codec now supports all error handlers, instead of only |
| ``replace`` to encode and ``ignore`` to decode. |
| |
| A new Windows-only codec has been added: ``cp65001`` (:issue:`13216`). It is the |
| Windows code page 65001 (Windows UTF-8, ``CP_UTF8``). For example, it is used |
| by ``sys.stdout`` if the console output code page is set to cp65001 (e.g., using |
| ``chcp 65001`` command). |
| |
| Multibyte CJK decoders now resynchronize faster. They only ignore the first |
| byte of an invalid byte sequence. For example, ``b'\xff\n'.decode('gb2312', |
| 'replace')`` now returns a ``\n`` after the replacement character. |
| |
| (:issue:`12016`) |
| |
| Incremental CJK codec encoders are no longer reset at each call to their |
| encode() methods. For example:: |
| |
| $ ./python -q |
| >>> import codecs |
| >>> encoder = codecs.getincrementalencoder('hz')('strict') |
| >>> b''.join(encoder.encode(x) for x in '\u52ff\u65bd\u65bc\u4eba\u3002 Bye.') |
| b'~{NpJ)l6HK!#~} Bye.' |
| |
| This example gives ``b'~{Np~}~{J)~}~{l6~}~{HK~}~{!#~} Bye.'`` with older Python |
| versions. |
| |
| (:issue:`12100`) |
| |
| The ``unicode_internal`` codec has been deprecated. |
| |
| |
| collections |
| ----------- |
| |
| Addition of a new :class:`~collections.ChainMap` class to allow treating a |
| number of mappings as a single unit. (Written by Raymond Hettinger for |
| :issue:`11089`, made public in :issue:`11297`) |
| |
| The abstract base classes have been moved in a new :mod:`collections.abc` |
| module, to better differentiate between the abstract and the concrete |
| collections classes. Aliases for ABCs are still present in the |
| :mod:`collections` module to preserve existing imports. (:issue:`11085`) |
| |
| .. XXX addition of __slots__ to ABCs not recorded here: internal detail |
| |
| The :class:`~collections.Counter` class now supports the unary ``+`` and ``-`` |
| operators, as well as the in-place operators ``+=``, ``-=``, ``|=``, and |
| ``&=``. (Contributed by Raymond Hettinger in :issue:`13121`.) |
| |
| |
| contextlib |
| ---------- |
| |
| :class:`~contextlib.ExitStack` now provides a solid foundation for |
| programmatic manipulation of context managers and similar cleanup |
| functionality. Unlike the previous ``contextlib.nested`` API (which was |
| deprecated and removed), the new API is designed to work correctly |
| regardless of whether context managers acquire their resources in |
| their ``__init__`` method (for example, file objects) or in their |
| ``__enter__`` method (for example, synchronisation objects from the |
| :mod:`threading` module). |
| |
| (:issue:`13585`) |
| |
| |
| crypt |
| ----- |
| |
| Addition of salt and modular crypt format (hashing method) and the :func:`~crypt.mksalt` |
| function to the :mod:`crypt` module. |
| |
| (:issue:`10924`) |
| |
| curses |
| ------ |
| |
| * If the :mod:`curses` module is linked to the ncursesw library, use Unicode |
| functions when Unicode strings or characters are passed (e.g. |
| :c:func:`waddwstr`), and bytes functions otherwise (e.g. :c:func:`waddstr`). |
| * Use the locale encoding instead of ``utf-8`` to encode Unicode strings. |
| * :class:`curses.window` has a new :attr:`curses.window.encoding` attribute. |
| * The :class:`curses.window` class has a new :meth:`~curses.window.get_wch` |
| method to get a wide character |
| * The :mod:`curses` module has a new :meth:`~curses.unget_wch` function to |
| push a wide character so the next :meth:`~curses.window.get_wch` will return |
| it |
| |
| (Contributed by Iñigo Serna in :issue:`6755`) |
| |
| datetime |
| -------- |
| |
| * Equality comparisons between naive and aware :class:`~datetime.datetime` |
| instances now return :const:`False` instead of raising :exc:`TypeError` |
| (:issue:`15006`). |
| * New :meth:`datetime.datetime.timestamp` method: Return POSIX timestamp |
| corresponding to the :class:`~datetime.datetime` instance. |
| * The :meth:`datetime.datetime.strftime` method supports formatting years |
| older than 1000. |
| * The :meth:`datetime.datetime.astimezone` method can now be |
| called without arguments to convert datetime instance to the system |
| timezone. |
| |
| |
| .. _new-decimal: |
| |
| decimal |
| ------- |
| |
| :issue:`7652` - integrate fast native decimal arithmetic. |
| C-module and libmpdec written by Stefan Krah. |
| |
| The new C version of the decimal module integrates the high speed libmpdec |
| library for arbitrary precision correctly-rounded decimal floating point |
| arithmetic. libmpdec conforms to IBM's General Decimal Arithmetic Specification. |
| |
| Performance gains range from 10x for database applications to 100x for |
| numerically intensive applications. These numbers are expected gains |
| for standard precisions used in decimal floating point arithmetic. Since |
| the precision is user configurable, the exact figures may vary. For example, |
| in integer bignum arithmetic the differences can be significantly higher. |
| |
| The following table is meant as an illustration. Benchmarks are available |
| at http://www.bytereef.org/mpdecimal/quickstart.html. |
| |
| +---------+-------------+--------------+-------------+ |
| | | decimal.py | _decimal | speedup | |
| +=========+=============+==============+=============+ |
| | pi | 42.02s | 0.345s | 120x | |
| +---------+-------------+--------------+-------------+ |
| | telco | 172.19s | 5.68s | 30x | |
| +---------+-------------+--------------+-------------+ |
| | psycopg | 3.57s | 0.29s | 12x | |
| +---------+-------------+--------------+-------------+ |
| |
| Features |
| ~~~~~~~~ |
| |
| * The :exc:`~decimal.FloatOperation` signal optionally enables stricter |
| semantics for mixing floats and Decimals. |
| |
| * If Python is compiled without threads, the C version automatically |
| disables the expensive thread local context machinery. In this case, |
| the variable :data:`~decimal.HAVE_THREADS` is set to ``False``. |
| |
| API changes |
| ~~~~~~~~~~~ |
| |
| * The C module has the following context limits, depending on the machine |
| architecture: |
| |
| +-------------------+---------------------+------------------------------+ |
| | | 32-bit | 64-bit | |
| +===================+=====================+==============================+ |
| | :const:`MAX_PREC` | :const:`425000000` | :const:`999999999999999999` | |
| +-------------------+---------------------+------------------------------+ |
| | :const:`MAX_EMAX` | :const:`425000000` | :const:`999999999999999999` | |
| +-------------------+---------------------+------------------------------+ |
| | :const:`MIN_EMIN` | :const:`-425000000` | :const:`-999999999999999999` | |
| +-------------------+---------------------+------------------------------+ |
| |
| * In the context templates (:class:`~decimal.DefaultContext`, |
| :class:`~decimal.BasicContext` and :class:`~decimal.ExtendedContext`) |
| the magnitude of :attr:`~decimal.Context.Emax` and |
| :attr:`~decimal.Context.Emin` has changed to :const:`999999`. |
| |
| * The :class:`~decimal.Decimal` constructor in decimal.py does not observe |
| the context limits and converts values with arbitrary exponents or precision |
| exactly. Since the C version has internal limits, the following scheme is |
| used: If possible, values are converted exactly, otherwise |
| :exc:`~decimal.InvalidOperation` is raised and the result is NaN. In the |
| latter case it is always possible to use :meth:`~decimal.Context.create_decimal` |
| in order to obtain a rounded or inexact value. |
| |
| |
| * The power function in decimal.py is always correctly-rounded. In the |
| C version, it is defined in terms of the correctly-rounded |
| :meth:`~decimal.Decimal.exp` and :meth:`~decimal.Decimal.ln` functions, |
| but the final result is only "almost always correctly rounded". |
| |
| |
| * In the C version, the context dictionary containing the signals is a |
| :class:`~collections.abc.MutableMapping`. For speed reasons, |
| :attr:`~decimal.Context.flags` and :attr:`~decimal.Context.traps` always |
| refer to the same :class:`~collections.abc.MutableMapping` that the context |
| was initialized with. If a new signal dictionary is assigned, |
| :attr:`~decimal.Context.flags` and :attr:`~decimal.Context.traps` |
| are updated with the new values, but they do not reference the RHS |
| dictionary. |
| |
| |
| * Pickling a :class:`~decimal.Context` produces a different output in order |
| to have a common interchange format for the Python and C versions. |
| |
| |
| * The order of arguments in the :class:`~decimal.Context` constructor has been |
| changed to match the order displayed by :func:`repr`. |
| |
| |
| * The ``watchexp`` parameter in the :meth:`~decimal.Decimal.quantize` method |
| is deprecated. |
| |
| |
| .. _new-email: |
| |
| email |
| ----- |
| |
| Policy Framework |
| ~~~~~~~~~~~~~~~~ |
| |
| The email package now has a :mod:`~email.policy` framework. A |
| :class:`~email.policy.Policy` is an object with several methods and properties |
| that control how the email package behaves. The primary policy for Python 3.3 |
| is the :class:`~email.policy.Compat32` policy, which provides backward |
| compatibility with the email package in Python 3.2. A ``policy`` can be |
| specified when an email message is parsed by a :mod:`~email.parser`, or when a |
| :class:`~email.message.Message` object is created, or when an email is |
| serialized using a :mod:`~email.generator`. Unless overridden, a policy passed |
| to a ``parser`` is inherited by all the ``Message`` object and sub-objects |
| created by the ``parser``. By default a ``generator`` will use the policy of |
| the ``Message`` object it is serializing. The default policy is |
| :data:`~email.policy.compat32`. |
| |
| The minimum set of controls implemented by all ``policy`` objects are: |
| |
| .. tabularcolumns:: |l|L| |
| |
| =============== ======================================================= |
| max_line_length The maximum length, excluding the linesep character(s), |
| individual lines may have when a ``Message`` is |
| serialized. Defaults to 78. |
| |
| linesep The character used to separate individual lines when a |
| ``Message`` is serialized. Defaults to ``\n``. |
| |
| cte_type ``7bit`` or ``8bit``. ``8bit`` applies only to a |
| ``Bytes`` ``generator``, and means that non-ASCII may |
| be used where allowed by the protocol (or where it |
| exists in the original input). |
| |
| raise_on_defect Causes a ``parser`` to raise error when defects are |
| encountered instead of adding them to the ``Message`` |
| object's ``defects`` list. |
| =============== ======================================================= |
| |
| A new policy instance, with new settings, is created using the |
| :meth:`~email.policy.Policy.clone` method of policy objects. ``clone`` takes |
| any of the above controls as keyword arguments. Any control not specified in |
| the call retains its default value. Thus you can create a policy that uses |
| ``\r\n`` linesep characters like this:: |
| |
| mypolicy = compat32.clone(linesep='\r\n') |
| |
| Policies can be used to make the generation of messages in the format needed by |
| your application simpler. Instead of having to remember to specify |
| ``linesep='\r\n'`` in all the places you call a ``generator``, you can specify |
| it once, when you set the policy used by the ``parser`` or the ``Message``, |
| whichever your program uses to create ``Message`` objects. On the other hand, |
| if you need to generate messages in multiple forms, you can still specify the |
| parameters in the appropriate ``generator`` call. Or you can have custom |
| policy instances for your different cases, and pass those in when you create |
| the ``generator``. |
| |
| |
| Provisional Policy with New Header API |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| While the policy framework is worthwhile all by itself, the main motivation for |
| introducing it is to allow the creation of new policies that implement new |
| features for the email package in a way that maintains backward compatibility |
| for those who do not use the new policies. Because the new policies introduce a |
| new API, we are releasing them in Python 3.3 as a :term:`provisional policy |
| <provisional package>`. Backwards incompatible changes (up to and including |
| removal of the code) may occur if deemed necessary by the core developers. |
| |
| The new policies are instances of :class:`~email.policy.EmailPolicy`, |
| and add the following additional controls: |
| |
| .. tabularcolumns:: |l|L| |
| |
| =============== ======================================================= |
| refold_source Controls whether or not headers parsed by a |
| :mod:`~email.parser` are refolded by the |
| :mod:`~email.generator`. It can be ``none``, ``long``, |
| or ``all``. The default is ``long``, which means that |
| source headers with a line longer than |
| ``max_line_length`` get refolded. ``none`` means no |
| line get refolded, and ``all`` means that all lines |
| get refolded. |
| |
| header_factory A callable that take a ``name`` and ``value`` and |
| produces a custom header object. |
| =============== ======================================================= |
| |
| The ``header_factory`` is the key to the new features provided by the new |
| policies. When one of the new policies is used, any header retrieved from |
| a ``Message`` object is an object produced by the ``header_factory``, and any |
| time you set a header on a ``Message`` it becomes an object produced by |
| ``header_factory``. All such header objects have a ``name`` attribute equal |
| to the header name. Address and Date headers have additional attributes |
| that give you access to the parsed data of the header. This means you can now |
| do things like this:: |
| |
| >>> m = Message(policy=SMTP) |
| >>> m['To'] = 'Éric <foo@example.com>' |
| >>> m['to'] |
| 'Éric <foo@example.com>' |
| >>> m['to'].addresses |
| (Address(display_name='Éric', username='foo', domain='example.com'),) |
| >>> m['to'].addresses[0].username |
| 'foo' |
| >>> m['to'].addresses[0].display_name |
| 'Éric' |
| >>> m['Date'] = email.utils.localtime() |
| >>> m['Date'].datetime |
| datetime.datetime(2012, 5, 25, 21, 39, 24, 465484, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000), 'EDT')) |
| >>> m['Date'] |
| 'Fri, 25 May 2012 21:44:27 -0400' |
| >>> print(m) |
| To: =?utf-8?q?=C3=89ric?= <foo@example.com> |
| Date: Fri, 25 May 2012 21:44:27 -0400 |
| |
| You will note that the unicode display name is automatically encoded as |
| ``utf-8`` when the message is serialized, but that when the header is accessed |
| directly, you get the unicode version. This eliminates any need to deal with |
| the :mod:`email.header` :meth:`~email.header.decode_header` or |
| :meth:`~email.header.make_header` functions. |
| |
| You can also create addresses from parts:: |
| |
| >>> m['cc'] = [Group('pals', [Address('Bob', 'bob', 'example.com'), |
| ... Address('Sally', 'sally', 'example.com')]), |
| ... Address('Bonzo', addr_spec='bonz@laugh.com')] |
| >>> print(m) |
| To: =?utf-8?q?=C3=89ric?= <foo@example.com> |
| Date: Fri, 25 May 2012 21:44:27 -0400 |
| cc: pals: Bob <bob@example.com>, Sally <sally@example.com>;, Bonzo <bonz@laugh.com> |
| |
| Decoding to unicode is done automatically:: |
| |
| >>> m2 = message_from_string(str(m)) |
| >>> m2['to'] |
| 'Éric <foo@example.com>' |
| |
| When you parse a message, you can use the ``addresses`` and ``groups`` |
| attributes of the header objects to access the groups and individual |
| addresses:: |
| |
| >>> m2['cc'].addresses |
| (Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com'), Address(display_name='Bonzo', username='bonz', domain='laugh.com')) |
| >>> m2['cc'].groups |
| (Group(display_name='pals', addresses=(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com')), Group(display_name=None, addresses=(Address(display_name='Bonzo', username='bonz', domain='laugh.com'),)) |
| |
| In summary, if you use one of the new policies, header manipulation works the |
| way it ought to: your application works with unicode strings, and the email |
| package transparently encodes and decodes the unicode to and from the RFC |
| standard Content Transfer Encodings. |
| |
| Other API Changes |
| ~~~~~~~~~~~~~~~~~ |
| |
| New :class:`~email.parser.BytesHeaderParser`, added to the :mod:`~email.parser` |
| module to complement :class:`~email.parser.HeaderParser` and complete the Bytes |
| API. |
| |
| New utility functions: |
| |
| * :func:`~email.utils.format_datetime`: given a :class:`~datetime.datetime`, |
| produce a string formatted for use in an email header. |
| |
| * :func:`~email.utils.parsedate_to_datetime`: given a date string from |
| an email header, convert it into an aware :class:`~datetime.datetime`, |
| or a naive :class:`~datetime.datetime` if the offset is ``-0000``. |
| |
| * :func:`~email.utils.localtime`: With no argument, returns the |
| current local time as an aware :class:`~datetime.datetime` using the local |
| :class:`~datetime.timezone`. Given an aware :class:`~datetime.datetime`, |
| converts it into an aware :class:`~datetime.datetime` using the |
| local :class:`~datetime.timezone`. |
| |
| |
| ftplib |
| ------ |
| |
| * :class:`ftplib.FTP` now accepts a ``source_address`` keyword argument to |
| specify the ``(host, port)`` to use as the source address in the bind call |
| when creating the outgoing socket. (Contributed by Giampaolo Rodolà |
| in :issue:`8594`.) |
| |
| * The :class:`~ftplib.FTP_TLS` class now provides a new |
| :func:`~ftplib.FTP_TLS.ccc` function to revert control channel back to |
| plaintext. This can be useful to take advantage of firewalls that know how |
| to handle NAT with non-secure FTP without opening fixed ports. (Contributed |
| by Giampaolo Rodolà in :issue:`12139`) |
| |
| * Added :meth:`ftplib.FTP.mlsd` method which provides a parsable directory |
| listing format and deprecates :meth:`ftplib.FTP.nlst` and |
| :meth:`ftplib.FTP.dir`. (Contributed by Giampaolo Rodolà in :issue:`11072`) |
| |
| |
| functools |
| --------- |
| |
| The :func:`functools.lru_cache` decorator now accepts a ``typed`` keyword |
| argument (that defaults to ``False`` to ensure that it caches values of |
| different types that compare equal in separate cache slots. (Contributed |
| by Raymond Hettinger in :issue:`13227`.) |
| |
| |
| gc |
| -- |
| |
| It is now possible to register callbacks invoked by the garbage collector |
| before and after collection using the new :data:`~gc.callbacks` list. |
| |
| |
| hmac |
| ---- |
| |
| A new :func:`~hmac.compare_digest` function has been added to prevent side |
| channel attacks on digests through timing analysis. (Contributed by Nick |
| Coghlan and Christian Heimes in :issue:`15061`) |
| |
| |
| http |
| ---- |
| |
| :class:`http.server.BaseHTTPRequestHandler` now buffers the headers and writes |
| them all at once when :meth:`~http.server.BaseHTTPRequestHandler.end_headers` is |
| called. A new method :meth:`~http.server.BaseHTTPRequestHandler.flush_headers` |
| can be used to directly manage when the accumlated headers are sent. |
| (Contributed by Andrew Schaaf in :issue:`3709`.) |
| |
| :class:`http.server` now produces valid ``HTML 4.01 strict`` output. |
| (Contributed by Ezio Melotti in :issue:`13295`.) |
| |
| :class:`http.client.HTTPResponse` now has a |
| :meth:`~http.client.HTTPResponse.readinto` method, which means it can be used |
| as a :class:`io.RawIOBase` class. (Contributed by John Kuhn in |
| :issue:`13464`.) |
| |
| |
| html |
| ---- |
| |
| :class:`html.parser.HTMLParser` is now able to parse broken markup without |
| raising errors, therefore the *strict* argument of the constructor and the |
| :exc:`~html.parser.HTMLParseError` exception are now deprecated. |
| The ability to parse broken markup is the result of a number of bug fixes that |
| are also available on the latest bug fix releases of Python 2.7/3.2. |
| (Contributed by Ezio Melotti in :issue:`15114`, and :issue:`14538`, |
| :issue:`13993`, :issue:`13960`, :issue:`13358`, :issue:`1745761`, |
| :issue:`755670`, :issue:`13357`, :issue:`12629`, :issue:`1200313`, |
| :issue:`670664`, :issue:`13273`, :issue:`12888`, :issue:`7311`) |
| |
| A new :data:`~html.entities.html5` dictionary that maps HTML5 named character |
| references to the equivalent Unicode character(s) (e.g. ``html5['gt;'] == |
| '>'``) has been added to the :mod:`html.entities` module. The dictionary is |
| now also used by :class:`~html.parser.HTMLParser`. (Contributed by Ezio |
| Melotti in :issue:`11113` and :issue:`15156`) |
| |
| |
| imaplib |
| ------- |
| |
| The :class:`~imaplib.IMAP4_SSL` constructor now accepts an SSLContext |
| parameter to control parameters of the secure channel. |
| |
| (Contributed by Sijin Joseph in :issue:`8808`) |
| |
| |
| inspect |
| ------- |
| |
| A new :func:`~inspect.getclosurevars` function has been added. This function |
| reports the current binding of all names referenced from the function body and |
| where those names were resolved, making it easier to verify correct internal |
| state when testing code that relies on stateful closures. |
| |
| (Contributed by Meador Inge and Nick Coghlan in :issue:`13062`) |
| |
| A new :func:`~inspect.getgeneratorlocals` function has been added. This |
| function reports the current binding of local variables in the generator's |
| stack frame, making it easier to verify correct internal state when testing |
| generators. |
| |
| (Contributed by Meador Inge in :issue:`15153`) |
| |
| io |
| -- |
| |
| The :func:`~io.open` function has a new ``'x'`` mode that can be used to |
| exclusively create a new file, and raise a :exc:`FileExistsError` if the file |
| already exists. It is based on the C11 'x' mode to fopen(). |
| |
| (Contributed by David Townshend in :issue:`12760`) |
| |
| The constructor of the :class:`~io.TextIOWrapper` class has a new |
| *write_through* optional argument. If *write_through* is ``True``, calls to |
| :meth:`~io.TextIOWrapper.write` are guaranteed not to be buffered: any data |
| written on the :class:`~io.TextIOWrapper` object is immediately handled to its |
| underlying binary buffer. |
| |
| |
| itertools |
| --------- |
| |
| :func:`~itertools.accumulate` now takes an optional ``func`` argument for |
| providing a user-supplied binary function. |
| |
| |
| logging |
| ------- |
| |
| The :func:`~logging.basicConfig` function now supports an optional ``handlers`` |
| argument taking an iterable of handlers to be added to the root logger. |
| |
| A class level attribute :attr:`~logging.handlers.SysLogHandler.append_nul` has |
| been added to :class:`~logging.handlers.SysLogHandler` to allow control of the |
| appending of the ``NUL`` (``\000``) byte to syslog records, since for some |
| deamons it is required while for others it is passed through to the log. |
| |
| |
| |
| math |
| ---- |
| |
| The :mod:`math` module has a new function, :func:`~math.log2`, which returns |
| the base-2 logarithm of *x*. |
| |
| (Written by Mark Dickinson in :issue:`11888`). |
| |
| |
| mmap |
| ---- |
| |
| The :meth:`~mmap.mmap.read` method is now more compatible with other file-like |
| objects: if the argument is omitted or specified as ``None``, it returns the |
| bytes from the current file position to the end of the mapping. (Contributed |
| by Petri Lehtinen in :issue:`12021`.) |
| |
| |
| multiprocessing |
| --------------- |
| |
| The new :func:`multiprocessing.connection.wait` function allows to poll |
| multiple objects (such as connections, sockets and pipes) with a timeout. |
| (Contributed by Richard Oudkerk in :issue:`12328`.) |
| |
| :class:`multiprocessing.Connection` objects can now be transferred over |
| multiprocessing connections. |
| (Contributed by Richard Oudkerk in :issue:`4892`.) |
| |
| :class:`multiprocessing.Process` now accepts a ``daemon`` keyword argument |
| to override the default behavior of inheriting the ``daemon`` flag from |
| the parent process (:issue:`6064`). |
| |
| New attribute attribute :data:`multiprocessing.Process.sentinel` allows a |
| program to wait on multiple :class:`~multiprocessing.Process` objects at one |
| time using the appropriate OS primitives (for example, :mod:`select` on |
| posix systems). |
| |
| New methods :meth:`multiprocessing.pool.Pool.starmap` and |
| :meth:`~multiprocessing.pool.Pool.starmap_async` provide |
| :func:`itertools.starmap` equivalents to the existing |
| :meth:`multiprocessing.pool.Pool.map` and |
| :meth:`~multiprocessing.pool.Pool.map_async` functions. (Contributed by Hynek |
| Schlawack in :issue:`12708`.) |
| |
| |
| nntplib |
| ------- |
| |
| The :class:`nntplib.NNTP` class now supports the context management protocol to |
| unconditionally consume :exc:`socket.error` exceptions and to close the NNTP |
| connection when done:: |
| |
| >>> from nntplib import NNTP |
| >>> with NNTP('news.gmane.org') as n: |
| ... n.group('gmane.comp.python.committers') |
| ... |
| ('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers') |
| >>> |
| |
| (Contributed by Giampaolo Rodolà in :issue:`9795`) |
| |
| |
| os |
| -- |
| |
| * The :mod:`os` module has a new :func:`~os.pipe2` function that makes it |
| possible to create a pipe with :data:`~os.O_CLOEXEC` or |
| :data:`~os.O_NONBLOCK` flags set atomically. This is especially useful to |
| avoid race conditions in multi-threaded programs. |
| |
| * The :mod:`os` module has a new :func:`~os.sendfile` function which provides |
| an efficent "zero-copy" way for copying data from one file (or socket) |
| descriptor to another. The phrase "zero-copy" refers to the fact that all of |
| the copying of data between the two descriptors is done entirely by the |
| kernel, with no copying of data into userspace buffers. :func:`~os.sendfile` |
| can be used to efficiently copy data from a file on disk to a network socket, |
| e.g. for downloading a file. |
| |
| (Patch submitted by Ross Lagerwall and Giampaolo Rodolà in :issue:`10882`.) |
| |
| * To avoid race conditions like symlink attacks and issues with temporary |
| files and directories, it is more reliable (and also faster) to manipulate |
| file descriptors instead of file names. Python 3.3 enhances existing functions |
| and introduces new functions to work on file descriptors (:issue:`4761`, |
| :issue:`10755` and :issue:`14626`). |
| |
| - The :mod:`os` module has a new :func:`~os.fwalk` function similar to |
| :func:`~os.walk` except that it also yields file descriptors referring to the |
| directories visited. This is especially useful to avoid symlink races. |
| |
| - The following functions get new optional *dir_fd* (:ref:`paths relative to |
| directory descriptors <dir_fd>`) and/or *follow_symlinks* (:ref:`not |
| following symlinks <follow_symlinks>`): |
| :func:`~os.access`, :func:`~os.chflags`, :func:`~os.chmod`, :func:`~os.chown`, |
| :func:`~os.link`, :func:`~os.lstat`, :func:`~os.mkdir`, :func:`~os.mkfifo`, |
| :func:`~os.mknod`, :func:`~os.open`, :func:`~os.readlink`, :func:`~os.remove`, |
| :func:`~os.rename`, :func:`~os.replace`, :func:`~os.rmdir`, :func:`~os.stat`, |
| :func:`~os.symlink`, :func:`~os.unlink`, :func:`~os.utime`. Platform |
| support for using these parameters can be checked via the sets |
| :data:`os.supports_dir_fd` and :data:`os.supports_follows_symlinks`. |
| |
| - The following functions now support a file descriptor for their path argument: |
| :func:`~os.chdir`, :func:`~os.chmod`, :func:`~os.chown`, |
| :func:`~os.execve`, :func:`~os.listdir`, :func:`~os.pathconf`, :func:`~os.path.exists`, |
| :func:`~os.stat`, :func:`~os.statvfs`, :func:`~os.utime`. Platform support |
| for this can be checked via the :data:`os.supports_fd` set. |
| |
| * :func:`~os.access` accepts an ``effective_ids`` keyword argument to turn on |
| using the effective uid/gid rather than the real uid/gid in the access check. |
| Platform support for this can be checked via the |
| :data:`~os.supports_effective_ids` set. |
| |
| * The :mod:`os` module has two new functions: :func:`~os.getpriority` and |
| :func:`~os.setpriority`. They can be used to get or set process |
| niceness/priority in a fashion similar to :func:`os.nice` but extended to all |
| processes instead of just the current one. |
| |
| (Patch submitted by Giampaolo Rodolà in :issue:`10784`.) |
| |
| * The new :func:`os.replace` function allows cross-platform renaming of a |
| file with overwriting the destination. With :func:`os.rename`, an existing |
| destination file is overwritten under POSIX, but raises an error under |
| Windows. |
| (Contributed by Antoine Pitrou in :issue:`8828`.) |
| |
| * The stat family of functions (:func:`~os.stat`, :func:`~os.fstat`, |
| and :func:`~os.lstat`) now support reading a file's timestamps |
| with nanosecond precision. Symmetrically, :func:`~os.utime` |
| can now write file timestamps with nanosecond precision. (Contributed by |
| Larry Hastings in :issue:`14127`.) |
| |
| * The new :func:`os.get_terminal_size` function queries the size of the |
| terminal attached to a file descriptor. See also |
| :func:`shutil.get_terminal_size`. |
| (Contributed by Zbigniew Jędrzejewski-Szmek in :issue:`13609`.) |
| |
| .. XXX sort out this mess after beta1 |
| |
| * New functions to support Linux extended attributes (:issue:`12720`): |
| :func:`~os.getxattr`, :func:`~os.listxattr`, :func:`~os.removexattr`, |
| :func:`~os.setxattr`. |
| |
| * New interface to the scheduler. These functions |
| control how a process is allocated CPU time by the operating system. New |
| functions: |
| :func:`~os.sched_get_priority_max`, :func:`~os.sched_get_priority_min`, |
| :func:`~os.sched_getaffinity`, :func:`~os.sched_getparam`, |
| :func:`~os.sched_getscheduler`, :func:`~os.sched_rr_get_interval`, |
| :func:`~os.sched_setaffinity`, :func:`~os.sched_setparam`, |
| :func:`~os.sched_setscheduler`, :func:`~os.sched_yield`, |
| |
| * New functions to control the file system: |
| |
| * :func:`~os.posix_fadvise`: Announces an intention to access data in a |
| specific pattern thus allowing the kernel to make optimizations. |
| * :func:`~os.posix_fallocate`: Ensures that enough disk space is allocated |
| for a file. |
| * :func:`~os.sync`: Force write of everything to disk. |
| |
| * Additional new posix functions: |
| |
| * :func:`~os.lockf`: Apply, test or remove a POSIX lock on an open file descriptor. |
| * :func:`~os.pread`: Read from a file descriptor at an offset, the file |
| offset remains unchanged. |
| * :func:`~os.pwrite`: Write to a file descriptor from an offset, leaving |
| the file offset unchanged. |
| * :func:`~os.readv`: Read from a file descriptor into a number of writable buffers. |
| * :func:`~os.truncate`: Truncate the file corresponding to *path*, so that |
| it is at most *length* bytes in size. |
| * :func:`~os.waitid`: Wait for the completion of one or more child processes. |
| * :func:`~os.writev`: Write the contents of *buffers* to a file descriptor, |
| where *buffers* is an arbitrary sequence of buffers. |
| * :func:`~os.getgrouplist` (:issue:`9344`): Return list of group ids that |
| specified user belongs to. |
| |
| * :func:`~os.times` and :func:`~os.uname`: Return type changed from a tuple to |
| a tuple-like object with named attributes. |
| |
| * Some platforms now support additional constants for the :func:`~os.lseek` |
| function, such as ``os.SEEK_HOLE`` and ``os.SEEK_DATA``. |
| |
| * New constants :data:`~os.RTLD_LAZY`, :data:`~os.RTLD_NOW`, |
| :data:`~os.RTLD_GLOBAL`, :data:`~os.RTLD_LOCAL`, :data:`~os.RTLD_NODELETE`, |
| :data:`~os.RTLD_NOLOAD`, and :data:`~os.RTLD_DEEPBIND` are available on |
| platforms that support them. These are for use with the |
| :func:`sys.setdlopenflags` function, and supersede the similar constants |
| defined in :mod:`ctypes` and :mod:`DLFCN`. (Contributed by Victor Stinner |
| in :issue:`13226`.) |
| |
| * :func:`os.symlink` now accepts (and ignores) the ``target_is_directory`` |
| keyword argument on non-Windows platforms, to ease cross-platform support. |
| |
| |
| pdb |
| --- |
| |
| Tab-completion is now available not only for command names, but also their |
| arguments. For example, for the ``break`` command, function and file names |
| are completed. |
| |
| (Contributed by Georg Brandl in :issue:`14210`) |
| |
| |
| pickle |
| ------ |
| |
| :class:`pickle.Pickler` objects now have an optional |
| :attr:`~pickle.Pickler.dispatch_table` attribute allowing to set per-pickler |
| reduction functions. |
| |
| (Contributed by Richard Oudkerk in :issue:`14166`.) |
| |
| |
| pydoc |
| ----- |
| |
| The Tk GUI and the :func:`~pydoc.serve` function have been removed from the |
| :mod:`pydoc` module: ``pydoc -g`` and :func:`~pydoc.serve` have been deprecated |
| in Python 3.2. |
| |
| |
| re |
| -- |
| |
| :class:`str` regular expressions now support ``\u`` and ``\U`` escapes. |
| |
| (Contributed by Serhiy Storchaka in :issue:`3665`.) |
| |
| |
| sched |
| ----- |
| |
| * :meth:`~sched.scheduler.run` now accepts a *blocking* parameter which when |
| set to False makes the method execute the scheduled events due to expire |
| soonest (if any) and then return immediately. |
| This is useful in case you want to use the :class:`~sched.scheduler` in |
| non-blocking applications. (Contributed by Giampaolo Rodolà in :issue:`13449`) |
| |
| * :class:`~sched.scheduler` class can now be safely used in multi-threaded |
| environments. (Contributed by Josiah Carlson and Giampaolo Rodolà in |
| :issue:`8684`) |
| |
| * *timefunc* and *delayfunct* parameters of :class:`~sched.scheduler` class |
| constructor are now optional and defaults to :func:`time.time` and |
| :func:`time.sleep` respectively. (Contributed by Chris Clark in |
| :issue:`13245`) |
| |
| * :meth:`~sched.scheduler.enter` and :meth:`~sched.scheduler.enterabs` |
| *argument* parameter is now optional. (Contributed by Chris Clark in |
| :issue:`13245`) |
| |
| * :meth:`~sched.scheduler.enter` and :meth:`~sched.scheduler.enterabs` |
| now accept a *kwargs* parameter. (Contributed by Chris Clark in |
| :issue:`13245`) |
| |
| |
| select |
| ------ |
| |
| Solaris and derivative platforms have a new class :class:`select.devpoll` |
| for high performance asynchronous sockets via :file:`/dev/poll`. |
| (Contributed by Jesús Cea Avión in :issue:`6397`.) |
| |
| |
| shlex |
| ----- |
| |
| The previously undocumented helper function ``quote`` from the |
| :mod:`pipes` modules has been moved to the :mod:`shlex` module and |
| documented. :func:`~shlex.quote` properly escapes all characters in a string |
| that might be otherwise given special meaning by the shell. |
| |
| |
| shutil |
| ------ |
| |
| * New functions: |
| |
| * :func:`~shutil.disk_usage`: provides total, used and free disk space |
| statistics. (Contributed by Giampaolo Rodolà in :issue:`12442`) |
| * :func:`~shutil.chown`: allows one to change user and/or group of the given |
| path also specifying the user/group names and not only their numeric |
| ids. (Contributed by Sandro Tosi in :issue:`12191`) |
| * :func:`shutil.get_terminal_size`: returns the size of the terminal window |
| to which the interpreter is attached. (Contributed by Zbigniew |
| Jędrzejewski-Szmek in :issue:`13609`.) |
| |
| * :func:`~shutil.copy2` and :func:`~shutil.copystat` now preserve file |
| timestamps with nanosecond precision on platforms that support it. |
| They also preserve file "extended attributes" on Linux. (Contributed |
| by Larry Hastings in :issue:`14127` and :issue:`15238`.) |
| |
| * Several functions now take an optional ``symlinks`` argument: when that |
| parameter is true, symlinks aren't dereferenced and the operation instead |
| acts on the symlink itself (or creates one, if relevant). |
| (Contributed by Hynek Schlawack in :issue:`12715`.) |
| |
| * When copying files to a different file system, :func:`~shutil.move` now |
| handles symlinks the way the posix ``mv`` command does, recreating the |
| symlink rather than copying the target file contents. (Contributed by |
| Jonathan Niehof in :issue:`9993`.) :func:`~shutil.move` now also returns |
| the ``dst`` argument as its result. |
| |
| * :func:`~shutil.rmtree` is now resistant to symlink attacks on platforms |
| which support the new ``dir_fd`` parameter in :func:`os.open` and |
| :func:`os.unlink`. (Contributed by Martin von Löwis and Hynek Schlawack |
| in :issue:`4489`.) |
| |
| |
| signal |
| ------ |
| |
| * The :mod:`signal` module has new functions: |
| |
| * :func:`~signal.pthread_sigmask`: fetch and/or change the signal mask of the |
| calling thread (Contributed by Jean-Paul Calderone in :issue:`8407`); |
| * :func:`~signal.pthread_kill`: send a signal to a thread; |
| * :func:`~signal.sigpending`: examine pending functions; |
| * :func:`~signal.sigwait`: wait a signal; |
| * :func:`~signal.sigwaitinfo`: wait for a signal, returning detailed |
| information about it; |
| * :func:`~signal.sigtimedwait`: like :func:`~signal.sigwaitinfo` but with a |
| timeout. |
| |
| * The signal handler writes the signal number as a single byte instead of |
| a nul byte into the wakeup file descriptor. So it is possible to wait more |
| than one signal and know which signals were raised. |
| |
| * :func:`signal.signal` and :func:`signal.siginterrupt` raise an OSError, |
| instead of a RuntimeError: OSError has an errno attribute. |
| |
| |
| smtpd |
| ----- |
| |
| The :mod:`smtpd` module now supports :rfc:`5321` (extended SMTP) and :rfc:`1870` |
| (size extension). Per the standard, these extensions are enabled if and only |
| if the client initiates the session with an ``EHLO`` command. |
| |
| (Initial ``ELHO`` support by Alberto Trevino. Size extension by Juhana |
| Jauhiainen. Substantial additional work on the patch contributed by Michele |
| Orrù and Dan Boswell. :issue:`8739`) |
| |
| |
| smtplib |
| ------- |
| |
| The :class:`~smtplib.SMTP`, :class:`~smtplib.SMTP_SSL`, and |
| :class:`~smtplib.LMTP` classes now accept a ``source_address`` keyword argument |
| to specify the ``(host, port)`` to use as the source address in the bind call |
| when creating the outgoing socket. (Contributed by Paulo Scardine in |
| :issue:`11281`.) |
| |
| :class:`~smtplib.SMTP` now supports the context management protocol, allowing an |
| ``SMTP`` instance to be used in a ``with`` statement. (Contributed |
| by Giampaolo Rodolà in :issue:`11289`.) |
| |
| The :class:`~smtplib.SMTP_SSL` constructor and the :meth:`~smtplib.SMTP.starttls` |
| method now accept an SSLContext parameter to control parameters of the secure |
| channel. (Contributed by Kasun Herath in :issue:`8809`) |
| |
| |
| socket |
| ------ |
| |
| * The :class:`~socket.socket` class now exposes additional methods to process |
| ancillary data when supported by the underlying platform: |
| |
| * :func:`~socket.socket.sendmsg` |
| * :func:`~socket.socket.recvmsg` |
| * :func:`~socket.socket.recvmsg_into` |
| |
| (Contributed by David Watson in :issue:`6560`, based on an earlier patch by |
| Heiko Wundram) |
| |
| * The :class:`~socket.socket` class now supports the PF_CAN protocol family |
| (http://en.wikipedia.org/wiki/Socketcan), on Linux |
| (http://lwn.net/Articles/253425). |
| |
| (Contributed by Matthias Fuchs, updated by Tiago Gonçalves in :issue:`10141`) |
| |
| * The :class:`~socket.socket` class now supports the PF_RDS protocol family |
| (http://en.wikipedia.org/wiki/Reliable_Datagram_Sockets and |
| http://oss.oracle.com/projects/rds/). |
| |
| * The :class:`~socket.socket` class now supports the ``PF_SYSTEM`` protocol |
| family on OS X. (Contributed by Michael Goderbauer in :issue:`13777`.) |
| |
| * New function :func:`~socket.sethostname` allows the hostname to be set |
| on unix systems if the calling process has sufficient privileges. |
| (Contributed by Ross Lagerwall in :issue:`10866`.) |
| |
| |
| socketserver |
| ------------ |
| |
| :class:`~socketserver.BaseServer` now has an overridable method |
| :meth:`~socketserver.BaseServer.service_actions` that is called by the |
| :meth:`~socketserver.BaseServer.serve_forever` method in the service loop. |
| :class:`~socketserver.ForkingMixIn` now uses this to clean up zombie |
| child proceses. (Contributed by Justin Warkentin in :issue:`11109`.) |
| |
| |
| sqlite3 |
| ------- |
| |
| New :class:`sqlite3.Connection` method |
| :meth:`~sqlite3.Connection.set_trace_callback` can be used to capture a trace of |
| all sql commands processed by sqlite. (Contributed by Torsten Landschoff |
| in :issue:`11688`.) |
| |
| |
| ssl |
| --- |
| |
| * The :mod:`ssl` module has two new random generation functions: |
| |
| * :func:`~ssl.RAND_bytes`: generate cryptographically strong |
| pseudo-random bytes. |
| * :func:`~ssl.RAND_pseudo_bytes`: generate pseudo-random bytes. |
| |
| (Contributed by Victor Stinner in :issue:`12049`) |
| |
| * The :mod:`ssl` module now exposes a finer-grained exception hierarchy |
| in order to make it easier to inspect the various kinds of errors. |
| (Contributed by Antoine Pitrou in :issue:`11183`) |
| |
| * :meth:`~ssl.SSLContext.load_cert_chain` now accepts a *password* argument |
| to be used if the private key is encrypted. |
| (Contributed by Adam Simpkins in :issue:`12803`) |
| |
| * Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is |
| now supported through the :meth:`~ssl.SSLContext.load_dh_params` and |
| :meth:`~ssl.SSLContext.set_ecdh_curve` methods. |
| (Contributed by Antoine Pitrou in :issue:`13626` and :issue:`13627`) |
| |
| * SSL sockets have a new :meth:`~ssl.SSLSocket.get_channel_binding` method |
| allowing the implementation of certain authentication mechanisms such as |
| SCRAM-SHA-1-PLUS. (Contributed by Jacek Konieczny in :issue:`12551`) |
| |
| * You can query the SSL compression algorithm used by an SSL socket, thanks |
| to its new :meth:`~ssl.SSLSocket.compression` method. The new attribute |
| :attr:`~ssl.OP_NO_COMPRESSION` can be used to disable compression. |
| (Contributed by Antoine Pitrou in :issue:`13634`) |
| |
| * Support has been added for the Next Procotol Negotiation extension using |
| the :meth:`ssl.SSLContext.set_npn_protocols` method. |
| (Contributed by Colin Marc in :issue:`14204`) |
| |
| * SSL errors can now be introspected more easily thanks to |
| :attr:`~ssl.SSLError.library` and :attr:`~ssl.SSLError.reason` attributes. |
| (Contributed by Antoine Pitrou in :issue:`14837`) |
| |
| * The :func:`~ssl.get_server_certificate` function now supports IPv6. |
| (Contributed by Charles-François Natali in :issue:`11811`.) |
| |
| * New attribute :attr:`~ssl.OP_CIPHER_SERVER_PREFERENCE` allows setting |
| SSLv3 server sockets to use the server's cipher ordering preference rather |
| than the client's (:issue:`13635`). |
| |
| |
| stat |
| ---- |
| |
| The undocumented tarfile.filemode function has been moved to |
| :func:`stat.filemode`. It can be used to convert a file's mode to a string of |
| the form '-rwxrwxrwx'. |
| |
| (Contributed by Giampaolo Rodolà in :issue:`14807`) |
| |
| |
| struct |
| ------ |
| |
| The :mod:`struct` module now supports ``ssize_t`` and ``size_t`` via the |
| new codes ``n`` and ``N``, respectively. (Contributed by Antoine Pitrou |
| in :issue:`3163`.) |
| |
| |
| subprocess |
| ---------- |
| |
| Command strings can now be bytes objects on posix platforms. (Contributed by |
| Victor Stinner in :issue:`8513`.) |
| |
| A new constant :data:`~subprocess.DEVNULL` allows suppressing output in a |
| platform-independent fashion. (Contributed by Ross Lagerwall in |
| :issue:`5870`.) |
| |
| |
| sys |
| --- |
| |
| The :mod:`sys` module has a new :data:`~sys.thread_info` :term:`struct |
| sequence` holding informations about the thread implementation |
| (:issue:`11223`). |
| |
| |
| tarfile |
| ------- |
| |
| :mod:`tarfile` now supports ``lzma`` encoding via the :mod:`lzma` module. |
| (Contributed by Lars Gustäbel in :issue:`5689`.) |
| |
| |
| tempfile |
| -------- |
| |
| :class:`tempfile.SpooledTemporaryFile`\'s |
| :meth:`~tempfile.SpooledTemporaryFile.truncate` method now accepts |
| a ``size`` parameter. (Contributed by Ryan Kelly in :issue:`9957`.) |
| |
| |
| textwrap |
| -------- |
| |
| The :mod:`textwrap` module has a new :func:`~textwrap.indent` that makes |
| it straightforward to add a common prefix to selected lines in a block |
| of text (:issue:`13857`). |
| |
| |
| threading |
| --------- |
| |
| :class:`threading.Condition`, :class:`threading.Semaphore`, |
| :class:`threading.BoundedSemaphore`, :class:`threading.Event`, and |
| :class:`threading.Timer`, all of which used to be factory functions returning a |
| class instance, are now classes and may be subclassed. (Contributed by Éric |
| Araujo in :issue:`10968`). |
| |
| The :class:`threading.Thread` constructor now accepts a ``daemon`` keyword |
| argument to override the default behavior of inheriting the ``deamon`` flag |
| value from the parent thread (:issue:`6064`). |
| |
| The formerly private function ``_thread.get_ident`` is now available as the |
| public function :func:`threading.get_ident`. This eliminates several cases of |
| direct access to the ``_thread`` module in the stdlib. Third party code that |
| used ``_thread.get_ident`` should likewise be changed to use the new public |
| interface. |
| |
| |
| time |
| ---- |
| |
| The :pep:`418` added new functions to the :mod:`time` module: |
| |
| * :func:`~time.get_clock_info`: Get information on a clock. |
| * :func:`~time.monotonic`: Monotonic clock (cannot go backward), not affected |
| by system clock updates. |
| * :func:`~time.perf_counter`: Performance counter with the highest available |
| resolution to measure a short duration. |
| * :func:`~time.process_time`: Sum of the system and user CPU time of the |
| current process. |
| |
| Other new functions: |
| |
| * :func:`~time.clock_getres`, :func:`~time.clock_gettime` and |
| :func:`~time.clock_settime` functions with ``CLOCK_xxx`` constants. |
| (Contributed by Victor Stinner in :issue:`10278`) |
| |
| To improve cross platform consistency, :func:`~time.sleep` now raises a |
| :exc:`ValueError` when passed a negative sleep value. Previously this was an |
| error on posix, but produced an infinite sleep on Windows. |
| |
| |
| types |
| ----- |
| |
| Add a new :class:`types.MappingProxyType` class: Read-only proxy of a mapping. |
| (:issue:`14386`) |
| |
| |
| The new functions `types.new_class` and `types.prepare_class` provide support |
| for PEP 3115 compliant dynamic type creation. (:issue:`14588`) |
| |
| |
| unittest |
| -------- |
| |
| :meth:`.assertRaises`, :meth:`.assertRaisesRegex`, :meth:`.assertWarns`, and |
| :meth:`.assertWarnsRegex` now accept a keyword argument *msg* when used as |
| context managers. (Contributed by Ezio Melotti and Winston Ewert in |
| :issue:`10775`) |
| |
| :meth:`unittest.TestCase.run` now returns the :class:`~unittest.TestResult` |
| object. |
| |
| |
| urllib |
| ------ |
| |
| The :class:`~urllib.request.Request` class, now accepts a *method* argument |
| used by :meth:`~urllib.request.Request.get_method` to determine what HTTP method |
| should be used. For example, this will send a ``'HEAD'`` request:: |
| |
| >>> urlopen(Request('http://www.python.org', method='HEAD')) |
| |
| (:issue:`1673007`) |
| |
| |
| webbrowser |
| ---------- |
| |
| The :mod:`webbrowser` module supports more "browsers": Google Chrome (named |
| :program:`chrome`, :program:`chromium`, :program:`chrome-browser` or |
| :program:`chromium-browser` depending on the version and operating system), |
| and the generic launchers :program:`xdg-open`, from the FreeDesktop.org |
| project, and :program:`gvfs-open`, which is the default URI handler for GNOME |
| 3. (The former contributed by Arnaud Calmettes in :issue:`13620`, the latter |
| by Matthias Klose in :issue:`14493`) |
| |
| |
| xml.etree.ElementTree |
| --------------------- |
| |
| The :mod:`xml.etree.ElementTree` module now imports its C accelerator by |
| default; there is no longer a need to explicitly import |
| :mod:`xml.etree.cElementTree` (this module stays for backwards compatibility, |
| but is now deprecated). In addition, the ``iter`` family of methods of |
| :class:`~xml.etree.ElementTree.Element` has been optimized (rewritten in C). |
| The module's documentation has also been greatly improved with added examples |
| and a more detailed reference. |
| |
| |
| zlib |
| ---- |
| |
| New attribute :attr:`zlib.Decompress.eof` makes it possible to distinguish |
| between a properly-formed compressed stream and an incomplete or truncated one. |
| (Contributed by Nadeem Vawda in :issue:`12646`.) |
| |
| New attribute :attr:`zlib.ZLIB_RUNTIME_VERSION` reports the version string of |
| the underlying ``zlib`` library that is loaded at runtime. (Contributed by |
| Torsten Landschoff in :issue:`12306`.) |
| |
| |
| Optimizations |
| ============= |
| |
| Major performance enhancements have been added: |
| |
| * Thanks to :pep:`393`, some operations on Unicode strings have been optimized: |
| |
| * the memory footprint is divided by 2 to 4 depending on the text |
| * encode an ASCII string to UTF-8 doesn't need to encode characters anymore, |
| the UTF-8 representation is shared with the ASCII representation |
| * the UTF-8 encoder has been optimized |
| * repeating a single ASCII letter and getting a substring of a ASCII strings |
| is 4 times faster |
| |
| * UTF-8 is now 2x to 4x faster. UTF-16 encoding is now up to 10x faster. |
| |
| (contributed by Serhiy Storchaka, :issue:`14624`, :issue:`14738` and |
| :issue:`15026`.) |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| Changes to Python's build process and to the C API include: |
| |
| * New :pep:`3118` related function: |
| |
| * :c:func:`PyMemoryView_FromMemory` |
| |
| * :pep:`393` added new Unicode types, macros and functions: |
| |
| * High-level API: |
| |
| * :c:func:`PyUnicode_CopyCharacters` |
| * :c:func:`PyUnicode_FindChar` |
| * :c:func:`PyUnicode_GetLength`, :c:macro:`PyUnicode_GET_LENGTH` |
| * :c:func:`PyUnicode_New` |
| * :c:func:`PyUnicode_Substring` |
| * :c:func:`PyUnicode_ReadChar`, :c:func:`PyUnicode_WriteChar` |
| |
| * Low-level API: |
| |
| * :c:type:`Py_UCS1`, :c:type:`Py_UCS2`, :c:type:`Py_UCS4` types |
| * :c:type:`PyASCIIObject` and :c:type:`PyCompactUnicodeObject` structures |
| * :c:macro:`PyUnicode_READY` |
| * :c:func:`PyUnicode_FromKindAndData` |
| * :c:func:`PyUnicode_AsUCS4`, :c:func:`PyUnicode_AsUCS4Copy` |
| * :c:macro:`PyUnicode_DATA`, :c:macro:`PyUnicode_1BYTE_DATA`, |
| :c:macro:`PyUnicode_2BYTE_DATA`, :c:macro:`PyUnicode_4BYTE_DATA` |
| * :c:macro:`PyUnicode_KIND` with :c:type:`PyUnicode_Kind` enum: |
| :c:data:`PyUnicode_WCHAR_KIND`, :c:data:`PyUnicode_1BYTE_KIND`, |
| :c:data:`PyUnicode_2BYTE_KIND`, :c:data:`PyUnicode_4BYTE_KIND` |
| * :c:macro:`PyUnicode_READ`, :c:macro:`PyUnicode_READ_CHAR`, :c:macro:`PyUnicode_WRITE` |
| * :c:macro:`PyUnicode_MAX_CHAR_VALUE` |
| |
| * :c:macro:`PyArg_ParseTuple` now accepts a :class:`bytearray` for the ``c`` |
| format (:issue:`12380`). |
| |
| |
| |
| Deprecated |
| ========== |
| |
| Unsupported Operating Systems |
| ----------------------------- |
| |
| OS/2 and VMS are no longer supported due to the lack of a maintainer. |
| |
| Windows 2000 and Windows platforms which set ``COMSPEC`` to ``command.com`` |
| are no longer supported due to maintenance burden. |
| |
| OSF support, which was deprecated in 3.2, has been completely removed. |
| |
| |
| Deprecated Python modules, functions and methods |
| ------------------------------------------------ |
| |
| * Passing a non-empty string to ``object.__format__()`` is deprecated, and |
| will produce a :exc:`TypeError` in Python 3.4 (:issue:`9856`). |
| * The ``unicode_internal`` codec has been deprecated because of the |
| :pep:`393`, use UTF-8, UTF-16 (``utf-16-le`` or ``utf-16-be``), or UTF-32 |
| (``utf-32-le`` or ``utf-32-be``) |
| * :meth:`ftplib.FTP.nlst` and :meth:`ftplib.FTP.dir`: use |
| :meth:`ftplib.FTP.mlsd` |
| * :func:`platform.popen`: use the :mod:`subprocess` module. Check especially |
| the :ref:`subprocess-replacements` section (:issue:`11377`). |
| * :issue:`13374`: The Windows bytes API has been deprecated in the :mod:`os` |
| module. Use Unicode filenames, instead of bytes filenames, to not depend on |
| the ANSI code page anymore and to support any filename. |
| * :issue:`13988`: The :mod:`xml.etree.cElementTree` module is deprecated. The |
| accelerator is used automatically whenever available. |
| * The behaviour of :func:`time.clock` depends on the platform: use the new |
| :func:`time.perf_counter` or :func:`time.process_time` function instead, |
| depending on your requirements, to have a well defined behaviour. |
| * The :func:`os.stat_float_times` function is deprecated. |
| * :mod:`abc` module: |
| |
| * :class:`abc.abstractproperty` has been deprecated, use :class:`property` |
| with :func:`abc.abstractmethod` instead. |
| * :class:`abc.abstractclassmethod` has been deprecated, use |
| :class:`classmethod` with :func:`abc.abstractmethod` instead. |
| * :class:`abc.abstractstaticmethod` has been deprecated, use |
| :class:`staticmethod` with :func:`abc.abstractmethod` instead. |
| |
| * :mod:`importlib` package: |
| |
| * :meth:`importlib.abc.SourceLoader.path_mtime` is now deprecated in favour of |
| :meth:`importlib.abc.SourceLoader.path_stats` as bytecode files now store |
| both the modification time and size of the source file the bytecode file was |
| compiled from. |
| |
| |
| |
| |
| |
| Deprecated functions and types of the C API |
| ------------------------------------------- |
| |
| The :c:type:`Py_UNICODE` has been deprecated by :pep:`393` and will be |
| removed in Python 4. All functions using this type are deprecated: |
| |
| Unicode functions and methods using :c:type:`Py_UNICODE` and |
| :c:type:`Py_UNICODE*` types: |
| |
| * :c:macro:`PyUnicode_FromUnicode`: use :c:func:`PyUnicode_FromWideChar` or |
| :c:func:`PyUnicode_FromKindAndData` |
| * :c:macro:`PyUnicode_AS_UNICODE`, :c:func:`PyUnicode_AsUnicode`, |
| :c:func:`PyUnicode_AsUnicodeAndSize`: use :c:func:`PyUnicode_AsWideCharString` |
| * :c:macro:`PyUnicode_AS_DATA`: use :c:macro:`PyUnicode_DATA` with |
| :c:macro:`PyUnicode_READ` and :c:macro:`PyUnicode_WRITE` |
| * :c:macro:`PyUnicode_GET_SIZE`, :c:func:`PyUnicode_GetSize`: use |
| :c:macro:`PyUnicode_GET_LENGTH` or :c:func:`PyUnicode_GetLength` |
| * :c:macro:`PyUnicode_GET_DATA_SIZE`: use |
| ``PyUnicode_GET_LENGTH(str) * PyUnicode_KIND(str)`` (only work on ready |
| strings) |
| * :c:func:`PyUnicode_AsUnicodeCopy`: use :c:func:`PyUnicode_AsUCS4Copy` or |
| :c:func:`PyUnicode_AsWideCharString` |
| * :c:func:`PyUnicode_GetMax` |
| |
| |
| Functions and macros manipulating Py_UNICODE* strings: |
| |
| * :c:macro:`Py_UNICODE_strlen`: use :c:func:`PyUnicode_GetLength` or |
| :c:macro:`PyUnicode_GET_LENGTH` |
| * :c:macro:`Py_UNICODE_strcat`: use :c:func:`PyUnicode_CopyCharacters` or |
| :c:func:`PyUnicode_FromFormat` |
| * :c:macro:`Py_UNICODE_strcpy`, :c:macro:`Py_UNICODE_strncpy`, |
| :c:macro:`Py_UNICODE_COPY`: use :c:func:`PyUnicode_CopyCharacters` or |
| :c:func:`PyUnicode_Substring` |
| * :c:macro:`Py_UNICODE_strcmp`: use :c:func:`PyUnicode_Compare` |
| * :c:macro:`Py_UNICODE_strncmp`: use :c:func:`PyUnicode_Tailmatch` |
| * :c:macro:`Py_UNICODE_strchr`, :c:macro:`Py_UNICODE_strrchr`: use |
| :c:func:`PyUnicode_FindChar` |
| * :c:macro:`Py_UNICODE_FILL`: use :c:func:`PyUnicode_Fill` |
| * :c:macro:`Py_UNICODE_MATCH` |
| |
| Encoders: |
| |
| * :c:func:`PyUnicode_Encode`: use :c:func:`PyUnicode_AsEncodedObject` |
| * :c:func:`PyUnicode_EncodeUTF7` |
| * :c:func:`PyUnicode_EncodeUTF8`: use :c:func:`PyUnicode_AsUTF8` or |
| :c:func:`PyUnicode_AsUTF8String` |
| * :c:func:`PyUnicode_EncodeUTF32` |
| * :c:func:`PyUnicode_EncodeUTF16` |
| * :c:func:`PyUnicode_EncodeUnicodeEscape:` use |
| :c:func:`PyUnicode_AsUnicodeEscapeString` |
| * :c:func:`PyUnicode_EncodeRawUnicodeEscape:` use |
| :c:func:`PyUnicode_AsRawUnicodeEscapeString` |
| * :c:func:`PyUnicode_EncodeLatin1`: use :c:func:`PyUnicode_AsLatin1String` |
| * :c:func:`PyUnicode_EncodeASCII`: use :c:func:`PyUnicode_AsASCIIString` |
| * :c:func:`PyUnicode_EncodeCharmap` |
| * :c:func:`PyUnicode_TranslateCharmap` |
| * :c:func:`PyUnicode_EncodeMBCS`: use :c:func:`PyUnicode_AsMBCSString` or |
| :c:func:`PyUnicode_EncodeCodePage` (with ``CP_ACP`` code_page) |
| * :c:func:`PyUnicode_EncodeDecimal`, |
| :c:func:`PyUnicode_TransformDecimalToASCII` |
| |
| |
| Deprecated features |
| ------------------- |
| |
| The :mod:`array` module's ``'u'`` format code is now deprecated and will be |
| removed in Python 4 together with the rest of the (:c:type:`Py_UNICODE`) API. |
| |
| |
| Porting to Python 3.3 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes |
| that may require changes to your code. |
| |
| .. _portingpythoncode: |
| |
| Porting Python code |
| ------------------- |
| |
| * Hash randomization is enabled by default. Set the :envvar:`PYTHONHASHSEED` |
| environment variable to ``0`` to disable hash randomization. See also the |
| :meth:`object.__hash__` method. |
| |
| * :issue:`12326`: On Linux, sys.platform doesn't contain the major version |
| anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending |
| on the Linux version used to build Python. Replace sys.platform == 'linux2' |
| with sys.platform.startswith('linux'), or directly sys.platform == 'linux' if |
| you don't need to support older Python versions. |
| |
| * :issue:`13847`, :issue:`14180`: :mod:`time` and :mod:`datetime`: |
| :exc:`OverflowError` is now raised instead of :exc:`ValueError` if a |
| timestamp is out of range. :exc:`OSError` is now raised if C functions |
| :c:func:`gmtime` or :c:func:`localtime` failed. |
| |
| * The default finders used by import now utilize a cache of what is contained |
| within a specific directory. If you create a Python source file or sourceless |
| bytecode file, make sure to call :func:`importlib.invalidate_caches` to clear |
| out the cache for the finders to notice the new file. |
| |
| * :exc:`ImportError` now uses the full name of the module that was attemped to |
| be imported. Doctests that check ImportErrors' message will need to be |
| updated to use the full name of the module instead of just the tail of the |
| name. |
| |
| * The *index* argument to :func:`__import__` now defaults to 0 instead of -1 |
| and no longer support negative values. It was an oversight when :pep:`328` was |
| implemented that the default value remained -1. If you need to continue to |
| perform a relative import followed by an absolute import, then perform the |
| relative import using an index of 1, followed by another import using an |
| index of 0. It is preferred, though, that you use |
| :func:`importlib.import_module` rather than call :func:`__import__` directly. |
| |
| * :func:`__import__` no longer allows one to use an index value other than 0 |
| for top-level modules. E.g. ``__import__('sys', level=1)`` is now an error. |
| |
| * Because :attr:`sys.meta_path` and :attr:`sys.path_hooks` now have finders on |
| them by default, you will most likely want to use :meth:`list.insert` instead |
| of :meth:`list.append` to add to those lists. |
| |
| * Because ``None`` is now inserted into :attr:`sys.path_importer_cache`, if you |
| are clearing out entries in the dictionary of paths that do not have a |
| finder, you will need to remove keys paired with values of ``None`` **and** |
| :class:`imp.NullImporter` to be backwards-compatible. This will lead to extra |
| overhead on older versions of Python that re-insert ``None`` into |
| :attr:`sys.path_importer_cache` where it repesents the use of implicit |
| finders, but semantically it should not change anything. |
| |
| * :class:`importlib.abc.Finder` no longer specifies a `find_module()` abstract |
| method that must be implemented. If you were relying on subclasses to |
| implement that method, make sure to check for the method's existence first. |
| You will probably want to check for `find_loader()` first, though, in the |
| case of working with :term:`path entry finders <path entry finder>`. |
| |
| * :mod:`pkgutil` has been converted to use :mod:`importlib` internally. This |
| eliminates many edge cases where the old behaviour of the PEP 302 import |
| emulation failed to match the behaviour of the real import system. The |
| import emulation itself is still present, but is now deprecated. The |
| :func:`pkgutil.iter_importers` and :func:`pkgutil.walk_packages` functions |
| special case the standard import hooks so they are still supported even |
| though they do not provide the non-standard ``iter_modules()`` method. |
| |
| * A longstanding RFC-compliance bug (:issue:`1079`) in the parsing done by |
| :func:`email.header.decode_header` has been fixed. Code that uses the |
| standard idiom to convert encoded headers into unicode |
| (``str(make_header(decode_header(h))``) will see no change, but code that |
| looks at the individual tuples returned by decode_header will see that |
| whitespace that precedes or follows ``ASCII`` sections is now included in the |
| ``ASCII`` section. Code that builds headers using ``make_header`` should |
| also continue to work without change, since ``make_header`` continues to add |
| whitespace between ``ASCII`` and non-``ASCII`` sections if it is not already |
| present in the input strings. |
| |
| * :func:`email.utils.formataddr` now does the correct content transfer |
| encoding when passed non-``ASCII`` display names. Any code that depended on |
| the previous buggy behavior that preserved the non-``ASCII`` unicode in the |
| formatted output string will need to be changed (:issue:`1690608`). |
| |
| * :meth:`poplib.POP3.quit` may now raise protocol errors like all other |
| ``poplib`` methods. Code that assumes ``quit`` does not raise |
| :exc:`poplib.error_proto` errors may need to be changed if errors on ``quit`` |
| are encountered by a particular application (:issue:`11291`). |
| |
| * The ``strict`` argument to :class:`email.parser.Parser`, deprecated since |
| Python 2.4, has finally been removed. |
| |
| * The deprecated method ``unittest.TestCase.assertSameElements`` has been |
| removed. |
| |
| * The deprecated variable ``time.accept2dyear`` has been removed. |
| |
| * The deprecated ``Context._clamp`` attribute has been removed from the |
| :mod:`decimal` module. It was previously replaced by the public attribute |
| :attr:`~decimal.Context.clamp`. (See :issue:`8540`.) |
| |
| * The undocumented internal helper class ``SSLFakeFile`` has been removed |
| from :mod:`smtplib`, since its functionality has long been provided directly |
| by :meth:`socket.socket.makefile`. |
| |
| * Passing a negative value to :func:`time.sleep` on Windows now raises an |
| error instead of sleeping forever. It has always raised an error on posix. |
| |
| * The ``ast.__version__`` constant has been removed. If you need to |
| make decisions affected by the AST version, use :attr:`sys.version_info` |
| to make the decision. |
| |
| * Code that used to work around the fact that the :mod:`threading` module used |
| factory functions by subclassing the private classes will need to change to |
| subclass the now-public classes. |
| |
| * The undocumented debugging machinery in the threading module has been |
| removed, simplifying the code. This should have no effect on production |
| code, but is mentioned here in case any application debug frameworks were |
| interacting with it (:issue:`13550`). |
| |
| |
| Porting C code |
| -------------- |
| |
| * In the course of changes to the buffer API the undocumented |
| :c:member:`~Py_buffer.smalltable` member of the |
| :c:type:`Py_buffer` structure has been removed and the |
| layout of the :c:type:`PyMemoryViewObject` has changed. |
| |
| All extensions relying on the relevant parts in ``memoryobject.h`` |
| or ``object.h`` must be rebuilt. |
| |
| * Due to :ref:`PEP 393 <pep-393>`, the :c:type:`Py_UNICODE` type and all |
| functions using this type are deprecated (but will stay available for |
| at least five years). If you were using low-level Unicode APIs to |
| construct and access unicode objects and you want to benefit of the |
| memory footprint reduction provided by PEP 393, you have to convert |
| your code to the new :doc:`Unicode API <../c-api/unicode>`. |
| |
| However, if you only have been using high-level functions such as |
| :c:func:`PyUnicode_Concat()`, :c:func:`PyUnicode_Join` or |
| :c:func:`PyUnicode_FromFormat()`, your code will automatically take |
| advantage of the new unicode representations. |
| |
| * :c:func:`PyImport_GetMagicNumber` now returns -1 upon failure. |
| |
| * As a negative value for the *level* argument to :func:`__import__` is no |
| longer valid, the same now holds for :c:func:`PyImport_ImportModuleLevel`. |
| This also means that the value of *level* used by |
| :c:func:`PyImport_ImportModuleEx` is now 0 instead of -1. |
| |
| |
| Building C extensions |
| --------------------- |
| |
| * The range of possible file names for C extensions has been narrowed. |
| Very rarely used spellings have been suppressed: under POSIX, files |
| named ``xxxmodule.so``, ``xxxmodule.abi3.so`` and |
| ``xxxmodule.cpython-*.so`` are no longer recognized as implementing |
| the ``xxx`` module. If you had been generating such files, you have |
| to switch to the other spellings (i.e., remove the ``module`` string |
| from the file names). |
| |
| (implemented in :issue:`14040`.) |
| |
| |
| Command Line Switch Changes |
| --------------------------- |
| |
| * The -Q command-line flag and related artifacts have been removed. Code |
| checking sys.flags.division_warning will need updating. |
| |
| (:issue:`10998`, contributed by Éric Araujo.) |
| |
| * When :program:`python` is started with :option:`-S`, ``import site`` |
| will no longer add site-specific paths to the module search paths. In |
| previous versions, it did. |
| |
| (:issue:`11591`, contributed by Carl Meyer with editions by Éric Araujo.) |