Python3.4有什么新变化

abc¶

New function abc.get_cache_token() can be used to know when to invalidate

caches that are affected by changes in the object graph. (Contributed

by Łukasz Langa in bpo-16832.)

New class ABC has ABCMeta as its meta class.

Using ABC as a base class has essentially the same effect as specifying

metaclass=abc.ABCMeta, but is simpler to type and easier to read.

(Contributed by Bruno Dupuis in bpo-16049.)

aifc¶

The getparams() method now returns a namedtuple rather than a

plain tuple. (Contributed by Claudiu Popa in bpo-17818.)

aifc.open() now supports the context management protocol: when used in a

with block, the close() method of the returned

object will be called automatically at the end of the block. (Contributed by

Serhiy Storchacha in bpo-16486.)

The writeframesraw() and writeframes()

methods now accept any bytes-like object. (Contributed by Serhiy

Storchaka in bpo-8311.)

argparse¶

The FileType class now accepts encoding and

errors arguments, which are passed through to open(). (Contributed

by Lucas Maystre in bpo-11175.)

audioop¶

audioop now supports 24-bit samples. (Contributed by Serhiy Storchaka

in bpo-12866.)

New byteswap() function converts big-endian samples to

little-endian and vice versa. (Contributed by Serhiy Storchaka in

bpo-19641.)

All audioop functions now accept any bytes-like object. Strings

are not accepted: they didn't work before, now they raise an error right away.

(Contributed by Serhiy Storchaka in bpo-16685.)

base64¶

The encoding and decoding functions in base64 now accept any

bytes-like object in cases where it previously required a

bytes or bytearray instance. (Contributed by Nick Coghlan in

bpo-17839.)

New functions a85encode(), a85decode(),

b85encode(), and b85decode() provide the ability to

encode and decode binary data from and to Ascii85 and the git/mercurial

Base85 formats, respectively. The a85 functions have options that can

be used to make them compatible with the variants of the Ascii85 encoding,

including the Adobe variant. (Contributed by Martin Morrison, the Mercurial

project, Serhiy Storchaka, and Antoine Pitrou in bpo-17618.)

collections¶

The ChainMap.new_child() method now accepts an m argument specifying

the child map to add to the chain. This allows an existing mapping and/or a

custom mapping type to be used for the child. (Contributed by Vinay Sajip in

bpo-16613.)

colorsys¶

The number of digits in the coefficients for the RGB --- YIQ conversions have

been expanded so that they match the FCC NTSC versions. The change in

results should be less than 1% and may better match results found elsewhere.

(Contributed by Brian Landers and Serhiy Storchaka in bpo-14323.)

contextlib¶

The new contextlib.suppress context manager helps to clarify the

intent of code that deliberately suppresses exceptions from a single

statement. (Contributed by Raymond Hettinger in bpo-15806 and

Zero Piraeus in bpo-19266.)

The new contextlib.redirect_stdout() context manager makes it easier

for utility scripts to handle inflexible APIs that write their output to

sys.stdout and don't provide any options to redirect it. Using the

context manager, the sys.stdout output can be redirected to any

other stream or, in conjunction with io.StringIO, to a string.

The latter can be especially useful, for example, to capture output

from a function that was written to implement a command line interface.

It is recommended only for utility scripts because it affects the

global state of sys.stdout. (Contributed by Raymond Hettinger

in bpo-15805.)

The contextlib documentation has also been updated to include a

discussion of the

differences between single use, reusable and reentrant context managers.

dbm¶

dbm.open() objects now support the context management protocol. When

used in a with statement, the close method of the database

object will be called automatically at the end of the block. (Contributed by

Claudiu Popa and Nick Coghlan in bpo-19282.)

dis¶

Functions show_code(), dis(), distb(), and

disassemble() now accept a keyword-only file argument that

controls where they write their output.

The dis module is now built around an Instruction class

that provides object oriented access to the details of each individual bytecode

operation.

A new method, get_instructions(), provides an iterator that emits

the Instruction stream for a given piece of Python code. Thus it is now

possible to write a program that inspects and manipulates a bytecode

object in ways different from those provided by the dis module

itself. For example:

>>> importdis
>>> forinstrindis.get_instructions(lambdax:x+1):
... print(instr.opname)
LOAD_FAST
LOAD_CONST
BINARY_ADD
RETURN_VALUE

The various display tools in the dis module have been rewritten to use

these new components.

In addition, a new application-friendly class Bytecode provides

an object-oriented API for inspecting bytecode in both in human-readable form

and for iterating over instructions. The Bytecode constructor

takes the same arguments that get_instruction() does (plus an

optional current_offset), and the resulting object can be iterated to produce

Instruction objects. But it also has a dis

method, equivalent to calling dis on the constructor argument, but

returned as a multi-line string:

>>> bytecode=dis.Bytecode(lambdax:x+1,current_offset=3)
>>> forinstrinbytecode:
... print('{} ({})'.format(instr.opname,instr.opcode))
LOAD_FAST (124)
LOAD_CONST (100)
BINARY_ADD (23)
RETURN_VALUE (83)
>>> bytecode.dis().splitlines()
['  1           0 LOAD_FAST                0 (x)',
 '      -->     3 LOAD_CONST               1 (1)',
 '              6 BINARY_ADD',
 '              7 RETURN_VALUE']

Bytecode also has a class method,

from_traceback(), that provides the ability to manipulate a

traceback (that is, print(Bytecode.from_traceback(tb).dis()) is equivalent

to distb(tb)).

(Contributed by Nick Coghlan, Ryan Kelly and Thomas Kluyver in bpo-11816

and Claudiu Popa in bpo-17916.)

New function stack_effect() computes the effect on the Python stack

of a given opcode and argument, information that is not otherwise available.

(Contributed by Larry Hastings in bpo-19722.)

doctest¶

A new option flag, FAIL_FAST, halts

test running as soon as the first failure is detected. (Contributed by R.

David Murray and Daniel Urban in bpo-16522.)

The doctest command line interface now uses argparse, and has two

new options, -o and -f. -o allows doctest options to be specified on the command line, and -f is a

shorthand for -oFAIL_FAST (to parallel the similar option supported by the

unittest CLI). (Contributed by R. David Murray in bpo-11390.)

doctest will now find doctests in extension module __doc__ strings.

(Contributed by Zachary Ware in bpo-3158.)

email¶

as_string() now accepts a policy argument to

override the default policy of the message when generating a string

representation of it. This means that as_string can now be used in more

circumstances, instead of having to create and use a generator in

order to pass formatting parameters to its flatten method. (Contributed by

R. David Murray in bpo-18600.)

New method as_bytes() added to produce a bytes

representation of the message in a fashion similar to how as_string

produces a string representation. It does not accept the maxheaderlen

argument, but does accept the unixfrom and policy arguments. The

Message__bytes__() method

calls it, meaning that bytes(mymsg) will now produce the intuitive

result: a bytes object containing the fully formatted message. (Contributed

by R. David Murray in bpo-18600.)

The Message.set_param() message now accepts a replace keyword argument.

When specified, the associated header will be updated without changing

its location in the list of headers. For backward compatibility, the default

is False. (Contributed by R. David Murray in bpo-18891.)

A pair of new subclasses of Message have been added

(EmailMessage and MIMEPart), along with a new sub-module,

contentmanager and a new policy attribute

content_manager. All documentation is

currently in the new module, which is being added as part of email's new

provisional API. These classes provide a number of new methods that

make extracting content from and inserting content into email messages much

easier. For details, see the contentmanager documentation and

the email: 示例. These API additions complete the

bulk of the work that was planned as part of the email6 project. The currently

provisional API is scheduled to become final in Python 3.5 (possibly with a few

minor additions in the area of error handling). (Contributed by R. David

Murray in bpo-18891.)

filecmp¶

A new clear_cache() function provides the ability to clear the

filecmp comparison cache, which uses os.stat() information to

determine if the file has changed since the last compare. This can be used,

for example, if the file might have been changed and re-checked in less time

than the resolution of a particular filesystem's file modification time field.

(Contributed by Mark Levitt in bpo-18149.)

New module attribute DEFAULT_IGNORES provides the list of

directories that are used as the default value for the ignore parameter of

the dircmp() function. (Contributed by Eli Bendersky in

bpo-15442.)

functools¶

The new partialmethod() descriptor brings partial argument

application to descriptors, just as partial() provides

for normal callables. The new descriptor also makes it easier to get

arbitrary callables (including partial() instances)

to behave like normal instance methods when included in a class definition.

(Contributed by Alon Horev and Nick Coghlan in bpo-4331.)

The new singledispatch() decorator brings support for

single-dispatch generic functions to the Python standard library. Where

object oriented programming focuses on grouping multiple operations on a

common set of data into a class, a generic function focuses on grouping

multiple implementations of an operation that allows it to work with

different kinds of data.

total_ordering() now supports a return value of

NotImplemented from the underlying comparison function. (Contributed

by Katie Miller in bpo-10042.)

A pure-python version of the partial() function is now in the

stdlib; in CPython it is overridden by the C accelerated version, but it is

available for other implementations to use. (Contributed by Brian Thorne in

bpo-12428.)

gc¶

New function get_stats() returns a list of three per-generation

dictionaries containing the collections statistics since interpreter startup.

(Contributed by Antoine Pitrou in bpo-16351.)

glob¶

A new function escape() provides a way to escape special characters

in a filename so that they do not become part of the globbing expansion but are

instead matched literally. (Contributed by Serhiy Storchaka in bpo-8402.)

hashlib¶

A new hashlib.pbkdf2_hmac() function provides

the PKCS#5 password-based key derivation function 2. (Contributed by Christian

Heimes in bpo-18582.)

The name attribute of hashlib hash objects is now

a formally supported interface. It has always existed in CPython's

hashlib (although it did not return lower case names for all supported

hashes), but it was not a public interface and so some other Python

implementations have not previously supported it. (Contributed by Jason R.

Coombs in bpo-18532.)

hmac¶

hmac now accepts bytearray as well as bytes for the key

argument to the new() function, and the msg parameter to both the

new() function and the update() method now

accepts any type supported by the hashlib module. (Contributed

by Jonas Borgström in bpo-18240.)

The digestmod argument to the hmac.new() function may now be any hash

digest name recognized by hashlib. In addition, the current behavior in

which the value of digestmod defaults to MD5 is deprecated: in a

future version of Python there will be no default value. (Contributed by

Christian Heimes in bpo-17276.)

With the addition of block_size and name

attributes (and the formal documentation of the digest_size

attribute), the hmac module now conforms fully to the PEP 247 API.

(Contributed by Christian Heimes in bpo-18775.)

html¶

New function unescape() function converts HTML5 character references to

the corresponding Unicode characters. (Contributed by Ezio Melotti in

bpo-2927.)

HTMLParser accepts a new keyword argument

convert_charrefs that, when True, automatically converts all character

references. For backward-compatibility, its value defaults to False, but

it will change to True in a future version of Python, so you are invited to

set it explicitly and update your code to use this new feature. (Contributed

by Ezio Melotti in bpo-13633.)

The strict argument of HTMLParser is now deprecated.

(Contributed by Ezio Melotti in bpo-15114.)

http¶

send_error() now accepts an

optional additional explain parameter which can be used to provide an

extended error description, overriding the hardcoded default if there is one.

This extended error description will be formatted using the

error_message_format attribute and sent as the body

of the error response. (Contributed by Karl Cow in bpo-12921.)

The http.servercommand line interface now has

a -b/--bind option that causes the server to listen on a specific address.

(Contributed by Malte Swart in bpo-17764.)

idlelib 与 IDLE¶

Since idlelib implements the IDLE shell and editor and is not intended for

import by other programs, it gets improvements with every release. See

Lib/idlelib/NEWS.txt for a cumulative list of changes since 3.3.0,

as well as changes made in future 3.4.x releases. This file is also available

from the IDLE Help ‣ About IDLE dialog.

importlib¶

The InspectLoader ABC defines a new method,

source_to_code() that accepts source

data and a path and returns a code object. The default implementation

is equivalent to compile(data,path,'exec',dont_inherit=True).

(Contributed by Eric Snow and Brett Cannon in bpo-15627.)

InspectLoader also now has a default implementation

for the get_code() method. However,

it will normally be desirable to override the default implementation

for performance reasons. (Contributed by Brett Cannon in bpo-18072.)

The reload() function has been moved from imp to

importlib as part of the imp module deprecation. (Contributed by

Berker Peksag in bpo-18193.)

importlib.util now has a MAGIC_NUMBER attribute

providing access to the bytecode version number. This replaces the

get_magic() function in the deprecated imp module.

(Contributed by Brett Cannon in bpo-18192.)

New importlib.util functions cache_from_source()

and source_from_cache() replace the same-named functions

in the deprecated imp module. (Contributed by Brett Cannon in

bpo-18194.)

The importlib bootstrap NamespaceLoader now conforms to

the InspectLoader ABC, which means that runpy and

python-m can now be used with namespace packages. (Contributed

by Brett Cannon in bpo-18058.)

importlib.util has a new function decode_source()

that decodes source from bytes using universal newline processing. This is

useful for implementing InspectLoader.get_source() methods.

importlib.machinery.ExtensionFileLoader now has a

get_filename() method. This was

inadvertently omitted in the original implementation. (Contributed by Eric

Snow in bpo-19152.)

inspect¶

The inspect module now offers a basic command line interface to quickly display source code and other

information for modules, classes and functions. (Contributed by Claudiu Popa

and Nick Coghlan in bpo-18626.)

unwrap() makes it easy to unravel wrapper function chains

created by functools.wraps() (and any other API that sets the

__wrapped__ attribute on a wrapper function). (Contributed by

Daniel Urban, Aaron Iles and Nick Coghlan in bpo-13266.)

As part of the implementation of the new enum module, the

inspect module now has substantially better support for custom

__dir__ methods and dynamic class attributes provided through

metaclasses. (Contributed by Ethan Furman in bpo-18929 and

bpo-19030.)

getfullargspec() and getargspec()

now use the signature() API. This allows them to

support a much broader range of callables, including those with

__signature__ attributes, those with metadata provided by argument

clinic, functools.partial() objects and more. Note that, unlike

signature(), these functions still ignore __wrapped__

attributes, and report the already bound first argument for bound methods,

so it is still necessary to update your code to use

signature() directly if those features are desired.

(Contributed by Yury Selivanov in bpo-17481.)

signature() now supports duck types of CPython functions,

which adds support for functions compiled with Cython. (Contributed

by Stefan Behnel and Yury Selivanov in bpo-17159.)

ipaddress¶

ipaddress was added to the standard library in Python 3.3 as a

provisional API. With the release of Python 3.4, this qualification

has been removed: ipaddress is now considered a stable API, covered

by the normal standard library requirements to maintain backwards

compatibility.

A new is_global property is True if

an address is globally routeable. (Contributed by Peter Moody in

bpo-17400.)

logging¶

The TimedRotatingFileHandler has a new atTime

parameter that can be used to specify the time of day when rollover should

happen. (Contributed by Ronald Oussoren in bpo-9556.)

SocketHandler and

DatagramHandler now support Unix domain sockets (by

setting port to None). (Contributed by Vinay Sajip in commit

ce46195b56a9.)

fileConfig() now accepts a

configparser.RawConfigParser subclass instance for the fname

parameter. This facilitates using a configuration file when logging

configuration is just a part of the overall application configuration, or where

the application modifies the configuration before passing it to

fileConfig(). (Contributed by Vinay Sajip in

bpo-16110.)

Logging configuration data received from a socket via the

logging.config.listen() function can now be validated before being

processed by supplying a verification function as the argument to the new

verify keyword argument. (Contributed by Vinay Sajip in bpo-15452.)

marshal¶

The default marshal version has been bumped to 3. The code implementing

the new version restores the Python2 behavior of recording only one copy of

interned strings and preserving the interning on deserialization, and extends

this "one copy" ability to any object type (including handling recursive

references). This reduces both the size of .pyc files and the amount of

memory a module occupies in memory when it is loaded from a .pyc (or

.pyo) file. (Contributed by Kristján Valur Jónsson in bpo-16475,

with additional speedups by Antoine Pitrou in bpo-19219.)

mmap¶

mmap objects can now be weakrefed. (Contributed by Valerie Lambert in

bpo-4885.)

multiprocessing¶

On Unix two new start methods,

spawn and forkserver, have been added for starting processes using

multiprocessing. These make the mixing of processes with threads more

robust, and the spawn method matches the semantics that multiprocessing has

always used on Windows. New function

get_all_start_methods() reports all start methods

available on the platform, get_start_method() reports

the current start method, and set_start_method() sets

the start method. (Contributed by Richard Oudkerk in bpo-8713.)

multiprocessing also now has the concept of a context, which

determines how child processes are created. New function

get_context() returns a context that uses a specified

start method. It has the same API as the multiprocessing module itself,

so you can use it to create Pools and other

objects that will operate within that context. This allows a framework and an

application or different parts of the same application to use multiprocessing

without interfering with each other. (Contributed by Richard Oudkerk in

bpo-18999.)

Except when using the old fork start method, child processes no longer

inherit unneeded handles/file descriptors from their parents (part of

bpo-8713).

multiprocessing now relies on runpy (which implements the

-m switch) to initialise __main__ appropriately in child processes

when using the spawn or forkserver start methods. This resolves some

edge cases where combining multiprocessing, the -m command line switch,

and explicit relative imports could cause obscure failures in child

processes. (Contributed by Nick Coghlan in bpo-19946.)

operator¶

New function length_hint() provides an implementation of the

specification for how the __length_hint__() special method should

be used, as part of the PEP 424 formal specification of this language

feature. (Contributed by Armin Ronacher in bpo-16148.)

There is now a pure-python version of the operator module available for

reference and for use by alternate implementations of Python. (Contributed by

Zachary Ware in bpo-16694.)

os¶

There are new functions to get and set the inheritable flag of a file descriptor (os.get_inheritable(),

os.set_inheritable()) or a Windows handle

(os.get_handle_inheritable(), os.set_handle_inheritable()).

New function cpu_count() reports the number of CPUs available on the

platform on which Python is running (or None if the count can't be

determined). The multiprocessing.cpu_count() function is now implemented

in terms of this function). (Contributed by Trent Nelson, Yogesh Chaudhari,

Victor Stinner, and Charles-François Natali in bpo-17914.)

os.path.samestat() is now available on the Windows platform (and the

os.path.samefile() implementation is now shared between Unix and

Windows). (Contributed by Brian Curtin in bpo-11939.)

os.path.ismount() now recognizes volumes mounted below a drive

root on Windows. (Contributed by Tim Golden in bpo-9035.)

os.open() supports two new flags on platforms that provide them,

O_PATH (un-opened file descriptor), and O_TMPFILE

(unnamed temporary file; as of 3.4.0 release available only on Linux systems

with a kernel version of 3.11 or newer that have uapi headers). (Contributed

by Christian Heimes in bpo-18673 and Benjamin Peterson, respectively.)

pdb¶

pdb has been enhanced to handle generators, yield, and

yieldfrom in a more useful fashion. This is especially helpful when

debugging asyncio based programs. (Contributed by Andrew Svetlov and

Xavier de Gaye in bpo-16596.)

The print command has been removed from pdb, restoring access to the

Python print() function from the pdb command line. Python2's pdb did

not have a print command; instead, entering print executed the

print statement. In Python3 print was mistakenly made an alias for the

pdb p command. p, however, prints the repr of its argument,

not the str like the Python2 print command did. Worse, the Python3

pdbprint command shadowed the Python3 print function, making it

inaccessible at the pdb prompt. (Contributed by Connor Osborn in

bpo-18764.)

pickle¶

pickle now supports (but does not use by default) a new pickle protocol,

protocol 4. This new protocol addresses a number of issues that were present

in previous protocols, such as the serialization of nested classes, very large

strings and containers, and classes whose __new__() method takes

keyword-only arguments. It also provides some efficiency improvements.

plistlib¶

plistlib now has an API that is similar to the standard pattern for

stdlib serialization protocols, with new load(),

dump(), loads(), and dumps()

functions. (The older API is now deprecated.) In addition to the already

supported XML plist format (FMT_XML), it also now supports

the binary plist format (FMT_BINARY). (Contributed by Ronald

Oussoren and others in bpo-14455.)

poplib¶

Two new methods have been added to poplib: capa(),

which returns the list of capabilities advertised by the POP server, and

stls(), which switches a clear-text POP3 session into an

encrypted POP3 session if the POP server supports it. (Contributed by Lorenzo

Catucci in bpo-4473.)

pprint¶

The pprint module's PrettyPrinter class and its

pformat(), and pprint() functions have a new

option, compact, that controls how the output is formatted. Currently

setting compact to True means that sequences will be printed with as many

sequence elements as will fit within width on each (indented) line.

(Contributed by Serhiy Storchaka in bpo-19132.)

Long strings are now wrapped using Python's normal line continuation

syntax. (Contributed by Antoine Pitrou in bpo-17150.)

pty¶

pty.spawn() now returns the status value from os.waitpid() on

the child process, instead of None. (Contributed by Gregory P. Smith.)

pydoc¶

The pydoc module is now based directly on the inspect.signature()

introspection API, allowing it to provide signature information for a wider

variety of callable objects. This change also means that __wrapped__

attributes are now taken into account when displaying help information.

(Contributed by Larry Hastings in bpo-19674.)

The pydoc module no longer displays the self parameter for

already bound methods. Instead, it aims to always display the exact current

signature of the supplied callable. (Contributed by Larry Hastings in

bpo-20710.)

In addition to the changes that have been made to pydoc directly,

its handling of custom __dir__ methods and various descriptor

behaviours has also been improved substantially by the underlying changes in

the inspect module.

As the help() builtin is based on pydoc, the above changes also

affect the behaviour of help().

re¶

New fullmatch() function and regex.fullmatch() method anchor

the pattern at both ends of the string to match. This provides a way to be

explicit about the goal of the match, which avoids a class of subtle bugs where

$ characters get lost during code changes or the addition of alternatives

to an existing regular expression. (Contributed by Matthew Barnett in

bpo-16203.)

The repr of regex objects now includes the pattern

and the flags; the repr of match objects now

includes the start, end, and the part of the string that matched. (Contributed

by Hugo Lopes Tavares and Serhiy Storchaka in bpo-13592 and

bpo-17087.)

resource¶

New prlimit() function, available on Linux platforms with a

kernel version of 2.6.36 or later and glibc of 2.13 or later, provides the

ability to query or set the resource limits for processes other than the one

making the call. (Contributed by Christian Heimes in bpo-16595.)

On Linux kernel version 2.6.36 or later, there are also some new

Linux specific constants: RLIMIT_MSGQUEUE,

RLIMIT_NICE, RLIMIT_RTPRIO,

RLIMIT_RTTIME, and RLIMIT_SIGPENDING.

(Contributed by Christian Heimes in bpo-19324.)

On FreeBSD version 9 and later, there some new FreeBSD specific constants:

RLIMIT_SBSIZE, RLIMIT_SWAP, and

RLIMIT_NPTS. (Contributed by Claudiu Popa in

bpo-19343.)

select¶

epoll objects now support the context management protocol.

When used in a with statement, the close()

method will be called automatically at the end of the block. (Contributed

by Serhiy Storchaka in bpo-16488.)

devpoll objects now have fileno() and

close() methods, as well as a new attribute

closed. (Contributed by Victor Stinner in

bpo-18794.)

shelve¶

Shelf instances may now be used in with statements,

and will be automatically closed at the end of the with block.

(Contributed by Filip Gruszczyński in bpo-13896.)

shutil¶

copyfile() now raises a specific Error subclass,

SameFileError, when the source and destination are the same

file, which allows an application to take appropriate action on this specific

error. (Contributed by Atsuo Ishimoto and Hynek Schlawack in

bpo-1492704.)

smtpd¶

The SMTPServer and SMTPChannel classes now

accept a map keyword argument which, if specified, is passed in to

asynchat.async_chat as its map argument. This allows an application

to avoid affecting the global socket map. (Contributed by Vinay Sajip in

bpo-11959.)

smtplib¶

SMTPException is now a subclass of OSError, which allows

both socket level errors and SMTP protocol level errors to be caught in one

try/except statement by code that only cares whether or not an error occurred.

(Contributed by Ned Jackson Lovely in bpo-2118.)

socket¶

The socket module now supports the CAN_BCM protocol on

platforms that support it. (Contributed by Brian Thorne in bpo-15359.)

Socket objects have new methods to get or set their inheritable flag, get_inheritable() and

set_inheritable().

The socket.AF_* and socket.SOCK_* constants are now enumeration values

using the new enum module. This allows meaningful names to be printed

during debugging, instead of integer "magic numbers".

The AF_LINK constant is now available on BSD and OSX.

inet_pton() and inet_ntop() are now supported

on Windows. (Contributed by Atsuo Ishimoto in bpo-7171.)

sqlite3¶

A new boolean parameter to the connect() function, uri, can be

used to indicate that the database parameter is a uri (see the SQLite

URI documentation). (Contributed by poq in

bpo-13773.)

ssl¶

PROTOCOL_TLSv1_1 and PROTOCOL_TLSv1_2 (TLSv1.1 and

TLSv1.2 support) have been added; support for these protocols is only available if

Python is linked with OpenSSL 1.0.1 or later. (Contributed by Michele Orrù and

Antoine Pitrou in bpo-16692.)

New function create_default_context() provides a standard way to

obtain an SSLContext whose settings are intended to be a

reasonable balance between compatibility and security. These settings are

more stringent than the defaults provided by the SSLContext

constructor, and may be adjusted in the future, without prior deprecation, if

best-practice security requirements change. The new recommended best

practice for using stdlib libraries that support SSL is to use

create_default_context() to obtain an SSLContext

object, modify it if needed, and then pass it as the context argument

of the appropriate stdlib API. (Contributed by Christian Heimes

in bpo-19689.)

SSLContext method load_verify_locations()

accepts a new optional argument cadata, which can be used to provide PEM or

DER encoded certificates directly via strings or bytes, respectively.

(Contributed by Christian Heimes in bpo-18138.)

New function get_default_verify_paths() returns

a named tuple of the paths and environment variables that the

set_default_verify_paths() method uses to set

OpenSSL's default cafile and capath. This can be an aid in

debugging default verification issues. (Contributed by Christian Heimes

in bpo-18143.)

SSLContext has a new method,

cert_store_stats(), that reports the number of loaded

X.509 certs, X.509CA certs, and certificate revocation lists

(crls), as well as a get_ca_certs() method that

returns a list of the loaded CA certificates. (Contributed by Christian

Heimes in bpo-18147.)

If OpenSSL 0.9.8 or later is available, SSLContext has a new

attribute verify_flags that can be used to control the

certificate verification process by setting it to some combination of the new

constants VERIFY_DEFAULT, VERIFY_CRL_CHECK_LEAF,

VERIFY_CRL_CHECK_CHAIN, or VERIFY_X509_STRICT.

OpenSSL does not do any CRL verification by default. (Contributed by

Christien Heimes in bpo-8813.)

New SSLContext method load_default_certs()

loads a set of default "certificate authority" (CA) certificates from default

locations, which vary according to the platform. It can be used to load both

TLS web server authentication certificates

(purpose=SERVER_AUTH) for a client to use to verify a

server, and certificates for a server to use in verifying client certificates

(purpose=CLIENT_AUTH). (Contributed by Christian

Heimes in bpo-19292.)

Two new windows-only functions, enum_certificates() and

enum_crls() provide the ability to retrieve certificates,

certificate information, and CRLs from the Windows cert store. (Contributed

by Christian Heimes in bpo-17134.)

Support for server-side SNI (Server Name Indication) using the new

ssl.SSLContext.set_servername_callback() method.

(Contributed by Daniel Black in bpo-8109.)

The dictionary returned by SSLSocket.getpeercert() contains additional

X509v3 extension items: crlDistributionPoints, calIssuers, and

OCSP URIs. (Contributed by Christian Heimes in bpo-18379.)

stat¶

The stat module is now backed by a C implementation in _stat. A C

implementation is required as most of the values aren't standardized and

are platform-dependent. (Contributed by Christian Heimes in bpo-11016.)

The module supports new ST_MODE flags, S_IFDOOR,

S_IFPORT, and S_IFWHT. (Contributed by

Christian Hiemes in bpo-11016.)

struct¶

New function iter_unpack and a new

struct.Struct.iter_unpack() method on compiled formats provide streamed

unpacking of a buffer containing repeated instances of a given format of data.

(Contributed by Antoine Pitrou in bpo-17804.)

subprocess¶

check_output() now accepts an input argument that can

be used to provide the contents of stdin for the command that is run.

(Contributed by Zack Weinberg in bpo-16624.)

getstatus() and getstatusoutput() now

work on Windows. This change was actually inadvertently made in 3.3.4.

(Contributed by Tim Golden in bpo-10197.)

sunau¶

The getparams() method now returns a namedtuple rather than a

plain tuple. (Contributed by Claudiu Popa in bpo-18901.)

sunau.open() now supports the context management protocol: when used in a

with block, the close method of the returned object will be

called automatically at the end of the block. (Contributed by Serhiy Storchaka

in bpo-18878.)

AU_write.setsampwidth() now supports 24 bit samples, thus adding

support for writing 24 sample using the module. (Contributed by

Serhiy Storchaka in bpo-19261.)

The writeframesraw() and

writeframes() methods now accept any bytes-like

object. (Contributed by Serhiy Storchaka in bpo-8311.)

sys¶

New function sys.getallocatedblocks() returns the current number of

blocks allocated by the interpreter. (In CPython with the default

--with-pymalloc setting, this is allocations made through the

PyObject_Malloc() API.) This can be useful for tracking memory leaks,

especially if automated via a test suite. (Contributed by Antoine Pitrou

in bpo-13390.)

When the Python interpreter starts in interactive mode, it checks for an __interactivehook__ attribute

on the sys module. If the attribute exists, its value is called with no

arguments just before interactive mode is started. The check is made after the

PYTHONSTARTUP file is read, so it can be set there. The site

module sets it to a function that enables tab

completion and history saving (in ~/.python-history) if the platform

supports readline. If you do not want this (new) behavior, you can

override it in PYTHONSTARTUP, sitecustomize, or

usercustomize by deleting this attribute from sys (or setting it

to some other callable). (Contributed by Éric Araujo and Antoine Pitrou in

bpo-5845.)

tarfile¶

The tarfile module now supports a simple 命令行界面 when

called as a script directly or via -m. This can be used to create and

extract tarfile archives. (Contributed by Berker Peksag in bpo-13477.)

textwrap¶

The TextWrapper class has two new attributes/constructor

arguments: max_lines, which limits the number of

lines in the output, and placeholder, which is a

string that will appear at the end of the output if it has been truncated

because of max_lines. Building on these capabilities, a new convenience

function shorten() collapses all of the whitespace in the input

to single spaces and produces a single line of a given width that ends with

the placeholder (by default, [...]). (Contributed by Antoine Pitrou and

Serhiy Storchaka in bpo-18585 and bpo-18725.)

threading¶

The Thread object representing the main thread can be

obtained from the new main_thread() function. In normal

conditions this will be the thread from which the Python interpreter was

started. (Contributed by Andrew Svetlov in bpo-18882.)

回溯¶

A new traceback.clear_frames() function takes a traceback object

and clears the local variables in all of the frames it references,

reducing the amount of memory consumed. (Contributed by Andrew Kuchling in

bpo-1565525.)

types¶

A new DynamicClassAttribute() descriptor provides a way to define

an attribute that acts normally when looked up through an instance object, but

which is routed to the class__getattr__ when looked up through the

class. This allows one to have properties active on a class, and have virtual

attributes on the class with the same name (see Enum for an example).

(Contributed by Ethan Furman in bpo-19030.)

urllib¶

urllib.request now supports data: URLs via the

DataHandler class. (Contributed by Mathias Panzenböck

in bpo-16423.)

The http method that will be used by a Request class

can now be specified by setting a method

class attribute on the subclass. (Contributed by Jason R Coombs in

bpo-18978.)

Request objects are now reusable: if the

full_url or data

attributes are modified, all relevant internal properties are updated. This

means, for example, that it is now possible to use the same

Request object in more than one

OpenerDirector.open() call with different data arguments, or to

modify a Request's url rather than recomputing it

from scratch. There is also a new

remove_header() method that can be used to remove

headers from a Request. (Contributed by Alexey

Kachayev in bpo-16464, Daniel Wozniak in bpo-17485, and Damien Brecht

and Senthil Kumaran in bpo-17272.)

HTTPError objects now have a

headers attribute that provides access to the

HTTP response headers associated with the error. (Contributed by

Berker Peksag in bpo-15701.)

unittest¶

The TestCase class has a new method,

subTest(), that produces a context manager whose

with block becomes a "sub-test". This context manager allows a test

method to dynamically generate subtests by, say, calling the subTest

context manager inside a loop. A single test method can thereby produce an

indefinite number of separately-identified and separately-counted tests, all of

which will run even if one or more of them fail. For example:

classNumbersTest(unittest.TestCase):
deftest_even(self):
foriinrange(6):
withself.subTest(i=i):
self.assertEqual(i%2,0)

will result in six subtests, each identified in the unittest verbose output

with a label consisting of the variable name i and a particular value for

that variable (i=0, i=1, etc). See Distinguishing test iterations using subtests for the full

version of this example. (Contributed by Antoine Pitrou in bpo-16997.)

unittest.main() now accepts an iterable of test names for

defaultTest, where previously it only accepted a single test name as a

string. (Contributed by Jyrki Pulliainen in bpo-15132.)

If SkipTest is raised during test discovery (that is, at the

module level in the test file), it is now reported as a skip instead of an

error. (Contributed by Zach Ware in bpo-16935.)

discover() now sorts the discovered files to provide

consistent test ordering. (Contributed by Martin Melin and Jeff Ramnani in

bpo-16709.)

TestSuite now drops references to tests as soon as the test

has been run, if the test is successful. On Python interpreters that do

garbage collection, this allows the tests to be garbage collected if nothing

else is holding a reference to the test. It is possible to override this

behavior by creating a TestSuite subclass that defines a

custom _removeTestAtIndex method. (Contributed by Tom Wardill, Matt

McClure, and Andrew Svetlov in bpo-11798.)

A new test assertion context-manager, assertLogs(),

will ensure that a given block of code emits a log message using the

logging module. By default the message can come from any logger and

have a priority of INFO or higher, but both the logger name and an

alternative minimum logging level may be specified. The object returned by the

context manager can be queried for the LogRecords and/or

formatted messages that were logged. (Contributed by Antoine Pitrou in

bpo-18937.)

Test discovery now works with namespace packages (Contributed by Claudiu Popa

in bpo-17457.)

unittest.mock objects now inspect their specification signatures when

matching calls, which means an argument can now be matched by either position

or name, instead of only by position. (Contributed by Antoine Pitrou in

bpo-17015.)

mock_open() objects now have readline and readlines

methods. (Contributed by Toshio Kuratomi in bpo-17467.)

venv¶

venv now includes activation scripts for the csh and fish

shells. (Contributed by Andrew Svetlov in bpo-15417.)

EnvBuilder and the create() convenience function

take a new keyword argument with_pip, which defaults to False, that

controls whether or not EnvBuilder ensures that pip is

installed in the virtual environment. (Contributed by Nick Coghlan in

bpo-19552 as part of the PEP 453 implementation.)

wave¶

The getparams() method now returns a namedtuple rather than a

plain tuple. (Contributed by Claudiu Popa in bpo-17487.)

wave.open() now supports the context management protocol. (Contributed

by Claudiu Popa in bpo-17616.)

wave can now write output to unseekable files. (Contributed by David Jones, Guilherme Polo, and Serhiy

Storchaka in bpo-5202.)

The writeframesraw() and

writeframes() methods now accept any bytes-like

object. (Contributed by Serhiy Storchaka in bpo-8311.)

weakref¶

New WeakMethod class simulates weak references to bound

methods. (Contributed by Antoine Pitrou in bpo-14631.)

New finalize class makes it possible to register a callback

to be invoked when an object is garbage collected, without needing to

carefully manage the lifecycle of the weak reference itself. (Contributed by

Richard Oudkerk in bpo-15528.)

The callback, if any, associated with a ref is now

exposed via the __callback__ attribute. (Contributed

by Mark Dickinson in bpo-17643.)

xml.etree¶

A new parser, XMLPullParser, allows a

non-blocking applications to parse XML documents. An example can be

seen at Pull API进行非阻塞解析. (Contributed by Antoine

Pitrou in bpo-17741.)

The xml.etree.ElementTreetostring() and

tostringlist() functions, and the

ElementTree

write() method, now have a

short_empty_elementskeyword-only parameter

providing control over whether elements with no content are written in

abbreviated (<tag/>) or expanded (<tag></tag>) form. (Contributed by

Ariel Poliak and Serhiy Storchaka in bpo-14377.)

zipfile¶

The writepy() method of the

PyZipFile class has a new filterfunc option that can be

used to control which directories and files are added to the archive. For

example, this could be used to exclude test files from the archive.

(Contributed by Christian Tismer in bpo-19274.)

The allowZip64 parameter to ZipFile and

PyZipfile is now True by default. (Contributed by

William Mallard in bpo-17201.)

PEP 445: Customization of CPython Memory Allocators¶

PEP 445 adds new C level interfaces to customize memory allocation in

the CPython interpreter.

PEP 442: Safe Object Finalization¶

PEP 442 removes the current limitations and quirks of object finalization

in CPython. With it, objects with __del__() methods, as well as

generators with finally clauses, can be finalized when they are

part of a reference cycle.

As part of this change, module globals are no longer forcibly set to

None during interpreter shutdown in most cases, instead relying

on the normal operation of the cyclic garbage collector. This avoids a

whole class of interpreter-shutdown-time errors, usually involving

__del__ methods, that have plagued Python since the cyclic GC

was first introduced.

PEP 456: Secure and Interchangeable Hash Algorithm¶

PEP 456 follows up on earlier security fix work done on Python's hash

algorithm to address certain DOS attacks to which public facing APIs backed by

dictionary lookups may be subject. (See bpo-14621 for the start of the

current round of improvements.) The PEP unifies CPython's hash code to make it

easier for a packager to substitute a different hash algorithm, and switches

Python's default implementation to a SipHash implementation on platforms that

have a 64 bit data type. Any performance differences in comparison with the

older FNV algorithm are trivial.

The PEP adds additional fields to the sys.hash_info named tuple to

describe the hash algorithm in use by the currently executing binary. Otherwise,

the PEP does not alter any existing CPython APIs.

PEP 436: Argument Clinic¶

"Argument Clinic" (PEP 436) is now part of the CPython build process

and can be used to simplify the process of defining and maintaining

accurate signatures for builtins and standard library extension modules

implemented in C.

Some standard library extension modules have been converted to use Argument

Clinic in Python 3.4, and pydoc and inspect have been updated

accordingly.

It is expected that signature metadata for programmatic introspection will

be added to additional callables implemented in C as part of Python 3.4

maintenance releases.

Other Build and C API Changes¶

• The new PyType_GetSlot() function has been added to the stable ABI,

  allowing retrieval of function pointers from named type slots when using

  the limited API. (Contributed by Martin von Löwis in bpo-17162.)

• The new Py_SetStandardStreamEncoding() pre-initialization API

  allows applications embedding the CPython interpreter to reliably force

  a particular encoding and error handler for the standard streams.

  (Contributed by Bastien Montagne and Nick Coghlan in bpo-16129.)

• Most Python C APIs that don't mutate string arguments are now correctly

  marked as accepting constchar* rather than char*. (Contributed

  by Serhiy Storchaka in bpo-1772673.)

• A new shell version of python-config can be used even when a python

  interpreter is not available (for example, in cross compilation scenarios).

• PyUnicode_FromFormat() now supports width and precision

  specifications for %s, %A, %U, %V, %S, and %R.

  (Contributed by Ysj Ray and Victor Stinner in bpo-7330.)

• New function PyStructSequence_InitType2() supplements the

  existing PyStructSequence_InitType() function. The difference

  is that it returns 0 on success and -1 on failure.

• The CPython source can now be compiled using the address sanity checking

  features of recent versions of GCC and clang: the false alarms in the small

  object allocator have been silenced. (Contributed by Dhiru Kholia in

  bpo-18596.)

• The Windows build now uses Address Space Layout Randomization and Data Execution Prevention. (Contributed by

  Christian Heimes in bpo-16632.)

• New function PyObject_LengthHint() is the C API equivalent

  of operator.length_hint(). (Contributed by Armin Ronacher in

  bpo-16148.)

其他改进¶

• The python command has a new option, -I, which causes it to run in "isolated mode",

  which means that sys.path contains neither the script's directory nor

  the user's site-packages directory, and all PYTHON* environment

  variables are ignored (it implies both -s and -E). Other

  restrictions may also be applied in the future, with the goal being to

  isolate the execution of a script from the user's environment. This is

  appropriate, for example, when Python is used to run a system script. On

  most POSIX systems it can and should be used in the #! line of system

  scripts. (Contributed by Christian Heimes in bpo-16499.)

• Tab-completion is now enabled by default in the interactive interpreter

  on systems that support readline. History is also enabled by default,

  and is written to (and read from) the file ~/.python-history.

  (Contributed by Antoine Pitrou and Éric Araujo in bpo-5845.)

• Invoking the Python interpreter with --version now outputs the version to

  standard output instead of standard error (bpo-18338). Similar changes

  were made to argparse (bpo-18920) and other modules that have

  script-like invocation capabilities (bpo-18922).

• The CPython Windows installer now adds .py to the PATHEXT

  variable when extensions are registered, allowing users to run a python

  script at the windows command prompt by just typing its name without the

  .py extension. (Contributed by Paul Moore in bpo-18569.)

• A new make target coverage-report

  will build python, run the test suite, and generate an HTML coverage report

  for the C codebase using gcov and lcov.

• The -R option to the python regression test suite now

  also checks for memory allocation leaks, using

  sys.getallocatedblocks(). (Contributed by Antoine Pitrou in

  bpo-13390.)

• python-m now works with namespace packages.

• The stat module is now implemented in C, which means it gets the

  values for its constants from the C header files, instead of having the

  values hard-coded in the python module as was previously the case.

• Loading multiple python modules from a single OS module (.so, .dll)

  now works correctly (previously it silently returned the first python

  module in the file). (Contributed by Václav Šmilauer in bpo-16421.)

• A new opcode, LOAD_CLASSDEREF, has been added to fix a bug in the

  loading of free variables in class bodies that could be triggered by certain

  uses of __prepare__. (Contributed by Benjamin Peterson in

  bpo-17853.)

• A number of MemoryError-related crashes were identified and fixed by Victor

  Stinner using his PEP 445-based pyfailmalloc tool (bpo-18408,

  bpo-18520).

• The pyvenv command now accepts a --copies option

  to use copies rather than symlinks even on systems where symlinks are the

  default. (Contributed by Vinay Sajip in bpo-18807.)

• The pyvenv command also accepts a --without-pip

  option to suppress the otherwise-automatic bootstrapping of pip into

  the virtual environment. (Contributed by Nick Coghlan in bpo-19552

  as part of the PEP 453 implementation.)

• The encoding name is now optional in the value set for the

  PYTHONIOENCODING environment variable. This makes it possible to

  set just the error handler, without changing the default encoding.

  (Contributed by Serhiy Storchaka in bpo-18818.)

• The bz2, lzma, and gzip module open functions now

  support x (exclusive creation) mode. (Contributed by Tim Heaney and

  Vajrasky Kok in bpo-19201, bpo-19222, and bpo-19223.)

Significant Optimizations¶

• The UTF-32 decoder is now 3x to 4x faster. (Contributed by Serhiy Storchaka

  in bpo-14625.)

• The cost of hash collisions for sets is now reduced. Each hash table

  probe now checks a series of consecutive, adjacent key/hash pairs before

  continuing to make random probes through the hash table. This exploits

  cache locality to make collision resolution less expensive.

  The collision resolution scheme can be described as a hybrid of linear

  probing and open addressing. The number of additional linear probes

  defaults to nine. This can be changed at compile-time by defining

  LINEAR_PROBES to be any value. Set LINEAR_PROBES=0 to turn-off

  linear probing entirely. (Contributed by Raymond Hettinger in

  bpo-18771.)

• The interpreter starts about 30% faster. A couple of measures lead to the

  speedup. The interpreter loads fewer modules on startup, e.g. the re,

  collections and locale modules and their dependencies are no

  longer imported by default. The marshal module has been improved to load

  compiled Python code faster. (Contributed by Antoine Pitrou, Christian

  Heimes and Victor Stinner in bpo-19219, bpo-19218, bpo-19209,

  bpo-19205 and bpo-9548.)

• bz2.BZ2File is now as fast or faster than the Python2 version for

  most cases. lzma.LZMAFile has also been optimized. (Contributed by

  Serhiy Storchaka and Nadeem Vawda in bpo-16034.)

• random.getrandbits() is 20%-40% faster for small integers (the most

  common use case). (Contributed by Serhiy Storchaka in bpo-16674.)

• By taking advantage of the new storage format for strings, pickling of

  strings is now significantly faster. (Contributed by Victor Stinner and

  Antoine Pitrou in bpo-15596.)

• A performance issue in io.FileIO.readall() has been solved. This

  particularly affects Windows, and significantly speeds up the case of piping

  significant amounts of data through subprocess. (Contributed

  by Richard Oudkerk in bpo-15758.)

• html.escape() is now 10x faster. (Contributed by Matt Bryant in

  bpo-18020.)

• On Windows, the native VirtualAlloc is now used instead of the CRT

  malloc in obmalloc. Artificial benchmarks show about a 3% memory

  savings.

• os.urandom() now uses a lazily-opened persistent file descriptor

  so as to avoid using many file descriptors when run in parallel from

  multiple threads. (Contributed by Antoine Pitrou in bpo-18756.)

Deprecations in the Python API¶

• As mentioned in PEP 451: A ModuleSpec Type for the Import System, a number of importlib

  methods and functions are deprecated: importlib.find_loader() is

  replaced by importlib.util.find_spec();

  importlib.machinery.PathFinder.find_module() is replaced by

  importlib.machinery.PathFinder.find_spec();

  importlib.abc.MetaPathFinder.find_module() is replaced by

  importlib.abc.MetaPathFinder.find_spec();

  importlib.abc.PathEntryFinder.find_loader() and

  find_module() are replaced by

  importlib.abc.PathEntryFinder.find_spec(); all of the xxxLoader ABC

  load_module methods (importlib.abc.Loader.load_module(),

  importlib.abc.InspectLoader.load_module(),

  importlib.abc.FileLoader.load_module(),

  importlib.abc.SourceLoader.load_module()) should no longer be

  implemented, instead loaders should implement an

  exec_module method

  (importlib.abc.Loader.exec_module(),

  importlib.abc.InspectLoader.exec_module()

  importlib.abc.SourceLoader.exec_module()) and let the import system

  take care of the rest; and

  importlib.abc.Loader.module_repr(),

  importlib.util.module_for_loader(), importlib.util.set_loader(),

  and importlib.util.set_package() are no longer needed because their

  functions are now handled automatically by the import system.

• The imp module is pending deprecation. To keep compatibility with

  Python 2/3 code bases, the module's removal is currently not scheduled.

• The formatter module is pending deprecation and is slated for removal

  in Python 3.6.

• MD5 as the default digestmod for the hmac.new() function is

  deprecated. Python 3.6 will require an explicit digest name or constructor as

  digestmod argument.

• The internal Netrc class in the ftplib module has been documented

  as deprecated in its docstring for quite some time. It now emits a

  DeprecationWarning and will be removed completely in Python 3.5.

• The undocumented endtime argument to subprocess.Popen.wait() should

  not have been exposed and is hopefully not in use; it is deprecated and

  will mostly likely be removed in Python 3.5.

• The strict argument of HTMLParser is deprecated.

• The plistlibreadPlist(),

  writePlist(), readPlistFromBytes(), and

  writePlistToBytes() functions are deprecated in favor of the

  corresponding new functions load(), dump(),

  loads(), and dumps(). Data()

  is deprecated in favor of just using the bytes constructor.

• The sysconfig key SO is deprecated, it has been replaced by

  EXT_SUFFIX.

• The U mode accepted by various open functions is deprecated.

  In Python3 it does not do anything useful, and should be replaced by

  appropriate uses of io.TextIOWrapper (if needed) and its newline

  argument.

• The parser argument of xml.etree.ElementTree.iterparse() has

  been deprecated, as has the html argument of

  XMLParser(). To prepare for the removal of the

  latter, all arguments to XMLParser should be passed by keyword.

Deprecated Features¶

• Running IDLE with the -n flag (no subprocess) is deprecated.

  However, the feature will not be removed until bpo-18823 is resolved.

• The site module adding a "site-python" directory to sys.path, if it

  exists, is deprecated (bpo-19375).

不再支持的操作系统¶

从源代码和构建工具中删除了对以下操作系统的支持：

• OS/2 (bpo-16135).

• Windows 2000（变更集e52df05b496a）。

• Windows系统中 COMSPEC 指向 command.com 的版本（ bpo-14470 ）。

• VMS (bpo-16136).

API 与特性的移除¶

The following obsolete and previously deprecated APIs and features have been

removed:

• The unmaintained Misc/TextMate and Misc/vim directories have been

  removed (see the devguide

  for suggestions on what to use instead).

• The SO makefile macro is removed (it was replaced by the

  SHLIB_SUFFIX and EXT_SUFFIX macros) (bpo-16754).

• The PyThreadState.tick_counter field has been removed; its value has

  been meaningless since Python 3.2, when the "new GIL" was introduced

  (bpo-19199).

• PyLoader and PyPycLoader have been removed from importlib.

  (Contributed by Taras Lyapun in bpo-15641.)

• The strict argument to HTTPConnection and

  HTTPSConnection has been removed. HTTP 0.9-style

  "Simple Responses" are no longer supported.

• The deprecated urllib.request.Request getter and setter methods

  add_data, has_data, get_data, get_type, get_host,

  get_selector, set_proxy, get_origin_req_host, and

  is_unverifiable have been removed (use direct attribute access instead).

• Support for loading the deprecated TYPE_INT64 has been removed from

  marshal. (Contributed by Dan Riti in bpo-15480.)

• inspect.Signature: positional-only parameters are now required

  to have a valid name.

• object.__format__() no longer accepts non-empty format strings, it now

  raises a TypeError instead. Using a non-empty string has been

  deprecated since Python 3.2. This change has been made to prevent a

  situation where previously working (but incorrect) code would start failing

  if an object gained a __format__ method, which means that your code may now

  raise a TypeError if you are using an 's' format code with objects

  that do not have a __format__ method that handles it. See bpo-7994 for

  background.

• difflib.SequenceMatcher.isbjunk() and

  difflib.SequenceMatcher.isbpopular() were deprecated in 3.2, and have

  now been removed: use xinsm.bjunk and

  xinsm.bpopular, where sm is a SequenceMatcher object

  (bpo-13248).

Code Cleanups¶

• The unused and undocumented internal Scanner class has been removed from

  the pydoc module.

• The private and effectively unused _gestalt module has been removed,

  along with the private platform functions _mac_ver_lookup,

  _mac_ver_gstalt, and _bcd2str, which would only have ever been called

  on badly broken OSX systems (see bpo-18393).

• The hardcoded copies of certain stat constants that were included in

  the tarfile module namespace have been removed.

 'python' 命令行为的变化¶

• In a posix shell, setting the PATH environment variable to

  an empty value is equivalent to not setting it at all. However, setting

  PYTHONPATH to an empty value was not equivalent to not setting it

  at all: setting PYTHONPATH to an empty value was equivalent to

  setting it to ., which leads to confusion when reasoning by analogy to

  how PATH works. The behavior now conforms to the posix convention

  for PATH.

• The [X refs, Y blocks] output of a debug (--with-pydebug) build of the

  CPython interpreter is now off by default. It can be re-enabled using the

  -Xshowrefcount option. (Contributed by Ezio Melotti in bpo-17323.)

• The python command and most stdlib scripts (as well as argparse) now

  output --version information to stdout instead of stderr (for

  issue list see 其他改进 above).

更改的Python API¶

• The ABCs defined in importlib.abc now either raise the appropriate

  exception or return a default value instead of raising

  NotImplementedError blindly. This will only affect code calling

  super() and falling through all the way to the ABCs. For compatibility,

  catch both NotImplementedError or the appropriate exception as needed.

• The module type now initializes the __package__ and __loader__

  attributes to None by default. To determine if these attributes were set

  in a backwards-compatible fashion, use e.g.

  getattr(module,'__loader__',None)isnotNone. (bpo-17115.)

• importlib.util.module_for_loader() now sets __loader__ and

  __package__ unconditionally to properly support reloading. If this is not

  desired then you will need to set these attributes manually. You can use

  importlib.util.module_to_load() for module management.

• Import now resets relevant attributes (e.g. __name__, __loader__,

  __package__, __file__, __cached__) unconditionally when reloading.

  Note that this restores a pre-3.3 behavior in that it means a module is

  re-found when re-loaded (bpo-19413).

• Frozen packages no longer set __path__ to a list containing the package

  name, they now set it to an empty list. The previous behavior could cause

  the import system to do the wrong thing on submodule imports if there was

  also a directory with the same name as the frozen package. The correct way

  to determine if a module is a package or not is to use hasattr(module,

  '__path__') (bpo-18065).

• Frozen modules no longer define a __file__ attribute. It's semantically

  incorrect for frozen modules to set the attribute as they are not loaded from

  any explicit location. If you must know that a module comes from frozen code

  then you can see if the module's __spec__.location is set to 'frozen',

  check if the loader is a subclass of

  importlib.machinery.FrozenImporter,

  or if Python 2 compatibility is necessary you can use imp.is_frozen().

• py_compile.compile() now raises FileExistsError if the file path

  it would write to is a symlink or a non-regular file. This is to act as a

  warning that import will overwrite those files with a regular file regardless

  of what type of file path they were originally.

• importlib.abc.SourceLoader.get_source() no longer raises

  ImportError when the source code being loaded triggers a

  SyntaxError or UnicodeDecodeError. As ImportError is

  meant to be raised only when source code cannot be found but it should, it was

  felt to be over-reaching/overloading of that meaning when the source code is

  found but improperly structured. If you were catching ImportError before and

  wish to continue to ignore syntax or decoding issues, catch all three

  exceptions now.

• functools.update_wrapper() and functools.wraps() now correctly

  set the __wrapped__ attribute to the function being wrapped, even if

  that function also had its __wrapped__ attribute set. This means

  __wrapped__ attributes now correctly link a stack of decorated

  functions rather than every __wrapped__ attribute in the chain

  referring to the innermost function. Introspection libraries that

  assumed the previous behaviour was intentional can use

  inspect.unwrap() to access the first function in the chain that has

  no __wrapped__ attribute.

• inspect.getfullargspec() has been reimplemented on top of

  inspect.signature() and hence handles a much wider variety of callable

  objects than it did in the past. It is expected that additional builtin and

  extension module callables will gain signature metadata over the course of

  the Python 3.4 series. Code that assumes that

  inspect.getfullargspec() will fail on non-Python callables may need

  to be adjusted accordingly.

• importlib.machinery.PathFinder now passes on the current working

  directory to objects in sys.path_hooks for the empty string. This

  results in sys.path_importer_cache never containing '', thus

  iterating through sys.path_importer_cache based on sys.path

  will not find all keys. A module's __file__ when imported in the current

  working directory will also now have an absolute path, including when using

  -m with the interpreter (except for __main__.__file__ when a script

  has been executed directly using a relative path) (Contributed by Brett

  Cannon in bpo-18416). is specified on the command-line)

  (bpo-18416).

• The removal of the strict argument to HTTPConnection

  and HTTPSConnection changes the meaning of the

  remaining arguments if you are specifying them positionally rather than by

  keyword. If you've been paying attention to deprecation warnings your code

  should already be specifying any additional arguments via keywords.

• Strings between from__future__import... statements now always raise

  a SyntaxError. Previously if there was no leading docstring, an

  interstitial string would sometimes be ignored. This brings CPython into

  compliance with the language spec; Jython and PyPy already were.

  (bpo-17434).

• ssl.SSLSocket.getpeercert() and ssl.SSLSocket.do_handshake()

  now raise an OSError with ENOTCONN when the SSLSocket is not

  connected, instead of the previous behavior of raising an

  AttributeError. In addition, getpeercert()

  will raise a ValueError if the handshake has not yet been done.

• base64.b32decode() now raises a binascii.Error when the

  input string contains non-b32-alphabet characters, instead of a

  TypeError. This particular TypeError was missed when the other

  TypeErrors were converted. (Contributed by Serhiy Storchaka in

  bpo-18011.) Note: this change was also inadvertently applied in Python

  3.3.3.

• The file attribute is now automatically closed when

  the creating cgi.FieldStorage instance is garbage collected. If you

  were pulling the file object out separately from the cgi.FieldStorage

  instance and not keeping the instance alive, then you should either store the

  entire cgi.FieldStorage instance or read the contents of the file

  before the cgi.FieldStorage instance is garbage collected.

• Calling read or write on a closed SSL socket now raises an

  informative ValueError rather than the previous more mysterious

  AttributeError (bpo-9177).

• slice.indices() no longer produces an OverflowError for huge

  values. As a consequence of this fix, slice.indices() now raises a

  ValueError if given a negative length; previously it returned nonsense

  values (bpo-14794).

• The complex constructor, unlike the cmath functions, was

  incorrectly accepting float values if an object's __complex__

  special method returned one. This now raises a TypeError.

  (bpo-16290.)

• The int constructor in 3.2 and 3.3 erroneously accepts float

  values for the base parameter. It is unlikely anyone was doing this, but

  if so, it will now raise a TypeError (bpo-16772).

• Defaults for keyword-only arguments are now evaluated after defaults for

  regular keyword arguments, instead of before. Hopefully no one wrote any

  code that depends on the previous buggy behavior (bpo-16967).

• Stale thread states are now cleared after fork(). This may cause

  some system resources to be released that previously were incorrectly kept

  perpetually alive (for example, database connections kept in thread-local

  storage). (bpo-17094.)

• Parameter names in __annotations__ dicts are now mangled properly,

  similarly to __kwdefaults__. (Contributed by Yury Selivanov in

  bpo-20625.)

• hashlib.hash.name now always returns the identifier in lower case.

  Previously some builtin hashes had uppercase names, but now that it is a

  formal public interface the naming has been made consistent (bpo-18532).

• Because unittest.TestSuite now drops references to tests after they

  are run, test harnesses that re-use a TestSuite to re-run

  a set of tests may fail. Test suites should not be re-used in this fashion

  since it means state is retained between test runs, breaking the test

  isolation that unittest is designed to provide. However, if the lack

  of isolation is considered acceptable, the old behavior can be restored by

  creating a TestSuite subclass that defines a

  _removeTestAtIndex method that does nothing (see

  TestSuite.__iter__()) (bpo-11798).

• unittest now uses argparse for command line parsing. There are

  certain invalid command forms that used to work that are no longer allowed;

  in theory this should not cause backward compatibility issues since the

  disallowed command forms didn't make any sense and are unlikely to be in use.

• The re.split(), re.findall(), and re.sub() functions, and

  the group() and groups() methods of

  match objects now always return a bytes object when the string

  to be matched is a bytes-like object. Previously the return type

  matched the input type, so if your code was depending on the return value

  being, say, a bytearray, you will need to change your code.

• audioop functions now raise an error immediately if passed string

  input, instead of failing randomly later on (bpo-16685).

• The new convert_charrefs argument to HTMLParser

  currently defaults to False for backward compatibility, but will

  eventually be changed to default to True. It is recommended that you add

  this keyword, with the appropriate value, to any

  HTMLParser calls in your code (bpo-13633).

• Since the digestmod argument to the hmac.new() function will in the

  future have no default, all calls to hmac.new() should be changed to

  explicitly specify a digestmod (bpo-17276).

• Calling sysconfig.get_config_var() with the SO key, or looking

  SO up in the results of a call to sysconfig.get_config_vars()

  is deprecated. This key should be replaced by EXT_SUFFIX or

  SHLIB_SUFFIX, depending on the context (bpo-19555).

• Any calls to open functions that specify U should be modified.

  U is ineffective in Python3 and will eventually raise an error if used.

  Depending on the function, the equivalent of its old Python2 behavior can be

  achieved using either a newline argument, or if necessary by wrapping the

  stream in TextIOWrapper to use its newline argument

  (bpo-15204).

• If you use pyvenv in a script and desire that pip

  not be installed, you must add --without-pip to your command

  invocation.

• The default behavior of json.dump() and json.dumps() when

  an indent is specified has changed: it no longer produces trailing

  spaces after the item separating commas at the ends of lines. This

  will matter only if you have tests that are doing white-space-sensitive

  comparisons of such output (bpo-16333).

• doctest now looks for doctests in extension module __doc__

  strings, so if your doctest test discovery includes extension modules that

  have things that look like doctests in them you may see test failures you've

  never seen before when running your tests (bpo-3158).

• The collections.abc module has been slightly refactored as

  part of the Python startup improvements. As a consequence of this, it is no

  longer the case that importing collections automatically imports

  collections.abc. If your program depended on the (undocumented)

  implicit import, you will need to add an explicit importcollections.abc

  (bpo-20784).

C API 中的改变¶

• PyEval_EvalFrameEx(), PyObject_Repr(), and

  PyObject_Str(), along with some other internal C APIs, now include

  a debugging assertion that ensures they are not used in situations where

  they may silently discard a currently active exception. In cases where

  discarding the active exception is expected and desired (for example,

  because it has already been saved locally with PyErr_Fetch() or

  is being deliberately replaced with a different exception), an explicit

  PyErr_Clear() call will be needed to avoid triggering the

  assertion when invoking these operations (directly or indirectly) and

  running against a version of Python that is compiled with assertions

  enabled.

• PyErr_SetImportError() now sets TypeError when its msg

  argument is not set. Previously only NULL was returned with no exception

  set.

• The result of the PyOS_ReadlineFunctionPointer callback must

  now be a string allocated by PyMem_RawMalloc() or

  PyMem_RawRealloc(), or NULL if an error occurred, instead of a

  string allocated by PyMem_Malloc() or PyMem_Realloc()

  (bpo-16742)

• PyThread_set_key_value() now always set the value. In Python

  3.3, the function did nothing if the key already exists (if the current

  value is a non-NULL pointer).

• The f_tstate (thread state) field of the PyFrameObject

  structure has been removed to fix a bug: see bpo-14432 for the

  rationale.

PEP 476: Enabling certificate verification by default for stdlib http clients¶

http.client and modules which use it, such as urllib.request and

xmlrpc.client, will now verify that the server presents a certificate

which is signed by a CA in the platform trust store and whose hostname matches

the hostname being requested by default, significantly improving security for

many applications.

For applications which require the old previous behavior, they can pass an

alternate context:

importurllib.request
importssl
# This disables all verification
context=ssl._create_unverified_context()
# This allows using a specific certificate for the host, which doesn't need
# to be in the trust store
context=ssl.create_default_context(cafile="/path/to/file.crt")
urllib.request.urlopen("https://invalid-cert",context=context)

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