What’s New In Python 3.5

Release:3.5.0a0 Date:July 03, 2014

This article explains the new features in Python 3.5, compared to 3.4.

For full details, see the Misc/NEWS file.

Note

Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.5 moves towards release, so it’s worth checking back even after reading earlier versions.

See also

Summary – Release highlights

New syntax features:

• None yet.

New library modules:

• None yet.

New built-in features:

• None yet.

Implementation improvements:

• When the LC_TYPE locale is the POSIX locale (C locale), sys.stdin and sys.stdout are now using the surrogateescape error handler, instead of the strict error handler (issue 19977).

Significantly Improved Library Modules:

• None yet.

Security improvements:

• None yet.

Please read on for a comprehensive list of user-facing changes.

Other Language Changes

Some smaller changes made to the core Python language are:

• None yet.

New Modules

• None yet.

Improved Modules

doctest

• doctest.DocTestSuite() returns an empty unittest.TestSuite if module contains no docstrings instead of raising ValueError (contributed by Glenn Jones in issue 15916).

imghdr

• what() now recognizes the OpenEXR format (contributed by Martin vignali and Cladui Popa in issue 20295).

importlib

• importlib.util.LazyLoader allows for the lazy loading of modules in applications where startup time is paramount (contributed by Brett Cannon in issue 17621).
• importlib.abc.InspectLoader.source_to_code() is now a static method to make it easier to work with source code in a string. With a module object that you want to initialize you can then use exec(code, module.__dict__) to execute the code in the module.
• importlib.util.module_from_spec() is now the preferred way to create a new module. Compared to types.ModuleType, this new function will set the various import-controlled attributes based on the passed-in spec object.

inspect

• inspect.Signature and inspect.Parameter are now picklable and hashable (contributed by Yury Selivanov in issue 20726 and issue 20334).
• New class method inspect.Signature.from_callable(), which makes subclassing of Signature easier (contributed by Yury Selivanov and Eric Snow in issue 17373).

ipaddress

• ipaddress.IPv4Network and ipaddress.IPv6Network now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses (contributed by Peter Moody and Antoine Pitrou in issue 16531).

os

• os.stat_result now has a st_file_attributes field on Windows, containing the dwFileAttributes member of the BY_HANDLE_FILE_INFORMATION structure returned by GetFileInformationByHandle() (contributed by Ben Hoyt in issue 21719).

shutil

• move() now accepts a copy_function argument, allowing, for example, copy() to be used instead of the default copy2() if there is a need to ignore metadata. (Contributed by Claudiu Popa in issue 19840.)

signal

• Different constants of signal module are now enumeration values using the enum module. This allows meaningful names to be printed during debugging, instead of integer “magic numbers”. (contributed by Giampaolo Rodola’ in issue 21076)

smtpd

• Both SMTPServer and smtpd.SMTPChannel now accept a decode_data keyword to determine if the DATA portion of the SMTP transaction is decoded using the utf-8 codec or is instead provided to process_message() as a byte string. The default is True for backward compatibility reasons, but will change to False in Python 3.6. (Contributed by Maciej Szulik in issue 19662.)
• It is now possible to provide, directly or via name resolution, IPv6 addresses in the SMTPServer constructor, and have it successfully connect. (Contributed by Milan Oberkirch in issue 14758.)

smtplib

• A new auth() method provides a convenient way to implement custom authentication mechanisms (contributed by Milan Oberkirch in issue 15014).

socket

• New socket.socket.sendfile() method allows to send a file over a socket by using high-performance os.sendfile() function on UNIX resulting in uploads being from 2x to 3x faster than when using plain socket.socket.send(). (contributed by Giampaolo Rodola’ in issue 17552)

wsgiref

• headers parameter of wsgiref.headers.Headers is now optional. (Contributed by Pablo Torres Navarrete and SilentGhost in issue 5800.)

xmlrpc

• xmlrpc.client.ServerProxy is now a context manager (contributed by Claudiu Popa in issue 20627).

Optimizations

The following performance enhancements have been added:

• Construction of bytes(int) (filled by zero bytes) is faster and use less memory for large objects. calloc() is used instead of malloc() to allocate memory for these objects.
• Some operations on IPv4Network and IPv6Network have been massively sped up, such as subnets(), supernet(), summarize_address_range(), collapse_addresses(). The speed up can range from 3x to 15x. (issue 21486, issue 21487, issue 20826)

Build and C API Changes

Changes to Python’s build process and to the C API include:

• New calloc functions:
  • PyMem_RawCalloc()
  • PyMem_Calloc()
  • PyObject_Calloc()
  • _PyObject_GC_Calloc()

Deprecated

Unsupported Operating Systems

• None yet.

Deprecated Python modules, functions and methods

• The formatter module has now graduated to full deprecation and is still slated for removal in Python 3.6.
• smtpd has in the past always decoded the DATA portion of email messages using the utf-8 codec. This can now be controlled by the new decode_data keyword to SMTPServer. The default value is True, but this default is deprecated. Specify the decode_data keyword with an appropriate value to avoid the deprecation warning.

Deprecated functions and types of the C API

• None yet.

Deprecated features

• None yet.

Porting to Python 3.5

This section lists previously described changes and other bugfixes that may require changes to your code.

Changes in the Python API

• Before Python 3.5, a datetime.time object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See issue 13936 for full details.
• ssl.SSLSocket.send() now raises either ssl.SSLWantReadError or ssl.SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. See issue 20951.
• The __name__ attribute of generator is now set from the function name, instead of being set from the code name. Use gen.gi_code.co_name to retrieve the code name. Generators also have a new __qualname__ attribute, the qualified name, which is now used for the representation of a generator (repr(gen)). See issue 21205.

Changes in the C API

• The PyMemAllocator structure was renamed to PyMemAllocatorEx and a new calloc field was added.