Python 3.5

Below is a list of finalised/accepted PEPs for Python 3.5 grouped into their impact to MicroPython.

Extensions to the syntax:


PEP 448

additional unpacking generalizations

PEP 465

a new matrix multiplication operator


PEP 492

coroutines with async and await syntax


Extensions and changes to runtime:

PEP 461

% formatting for binary strings


PEP 475

retrying system calls that fail with EINTR


PEP 479

change StopIteration handling inside generators


Standard library changes:

PEP 471


PEP 485

math.isclose(), a function for testing approximate equality


Miscellaneous changes:

PEP 441

improved Python zip application support

PEP 486

make the Python Laucher aware of virtual environments

PEP 484

type hints (advisory only)

In Progress

PEP 488

elimination of PYO files

Not relevant

PEP 489

redesigning extension module loading

Other Language Changes:

Added the namereplace error handlers. The backslashreplace error handlers now work with decoding and translating.

Property docstrings are now writable. This is especially useful for collections.namedtuple() docstrings

Circular imports involving relative imports are now supported.

New Modules:

Changes to built-in modules:


The OrderedDict class is now implemented in C, which makes it 4 to 100 times faster.

OrderedDict.items() , OrderedDict.keys() , OrderedDict.values() views now support reversed() iteration.

The deque class now defines index(), insert(), and copy(), and supports the + and * operators.

Docstrings produced by namedtuple() can now be updated.

The UserString class now implements the __getnewargs__(), __rmod__(), casefold(), format_map(), isprintable(), and maketrans() methods to match the corresponding methods of str.


Element comparison in merge() can now be customized by passing a key function in a new optional key keyword argument, and a new optional reverse keyword argument can be used to reverse element comparison


A new BufferedIOBase.readinto1() method, that uses at most one call to the underlying raw stream’s or RawIOBase.readinto() methods


JSON decoder now raises JSONDecodeError instead of ValueError to provide better context information about the error.


Two new constants have been added to the math module: inf and nan.

A new function isclose() provides a way to test for approximate equality.

A new gcd() function has been added. The fractions.gcd() function is now deprecated.


The new scandir() function returning an iterator of DirEntry objects has been added.

The urandom() function now uses the getrandom() syscall on Linux 3.17 or newer, and getentropy() on OpenBSD 5.6 and newer, removing the need to use /dev/urandom and avoiding failures due to potential file descriptor exhaustion.

New get_blocking() and set_blocking() functions allow getting and setting a file descriptor’s blocking mode (O_NONBLOCK.)

There is a new os.path.commonpath() function returning the longest common sub-path of each passed pathname


References and conditional references to groups with fixed length are now allowed in lookbehind assertions

The number of capturing groups in regular expressions is no longer limited to 100.

The sub() and subn() functions now replace unmatched groups with empty strings instead of raising an exception.

The re.error exceptions have new attributes, msg, pattern, pos, lineno, and colno, that provide better context information about the error


Functions with timeouts now use a monotonic clock, instead of a system clock.

A new socket.sendfile() method allows sending a file over a socket by using the high-performance os.sendfile() function on UNIX, resulting in uploads being from 2 to 3 times faster than when using plain socket.send()

The socket.sendall() method no longer resets the socket timeout every time bytes are received or sent. The socket timeout is now the maximum total duration to send all data.

The backlog argument of the socket.listen() method is now optional. By default it is set to SOMAXCONN or to 128, whichever is less.


Memory BIO Support

Application-Layer Protocol Negotiation Support

There is a new SSLSocket.version() method to query the actual protocol version in use.

The SSLSocket class now implements a SSLSocket.sendfile() method.

The SSLSocket.send() method now raises either the ssl.SSLWantReadError or ssl.SSLWantWriteError exception on a non-blocking socket if the operation would block. Previously, it would return 0.

The cert_time_to_seconds() function now interprets the input time as UTC and not as local time, per RFC 5280. Additionally, the return value is always an int.

New SSLObject.shared_ciphers() and SSLSocket.shared_ciphers() methods return the list of ciphers sent by the client during the handshake.

The SSLSocket.do_handshake(),, SSLSocket.shutdown(), and SSLSocket.write() methods of the SSLSocket class no longer reset the socket timeout every time bytes are received or sent.

The match_hostname() function now supports matching of IP addresses.


A new set_coroutine_wrapper() function allows setting a global hook that will be called whenever a coroutine object is created by an async def function. A corresponding get_coroutine_wrapper() can be used to obtain a currently set wrapper.

A new is_finalizing() function can be used to check if the Python interpreter is shutting down.


The monotonic() function is now always available