PEP 380：用于委托给子生成器的句法
¶
PEP 380 adds the
yield from
expression, allowing a
generator
to delegate part of its operations to another generator. This allows a section of code containing
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.
另请参阅
-
PEP 380
- 用于委托给子生成器的句法
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',)
另请参阅
-
PEP 409
- Suppressing exception context
-
PEP written by Ethan Furman; implemented by Ethan Furman and Nick Coghlan.
Using importlib as the Implementation of Import
¶
bpo-2377
- Replace __import__ w/ importlib.__import__
bpo-13959
- Re-implement parts of
imp
in pure Python
bpo-14605
- Make import machinery explicit
bpo-14646
- Require loaders set __loader__ and __package__
The
__import__()
function is now powered by
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
移植 Python 代码
section of this document.
Visible Changes
¶
For potential required changes to code, see the
移植 Python 代码
章节。
Beyond the expanse of what
importlib
now exposes, there are other visible changes to import. The biggest is that
sys.meta_path
and
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
importlib
and import itself is setting the attribute post-load.
None
is now inserted into
sys.path_importer_cache
when no finder can be found on
sys.path_hooks
。由于
imp.NullImporter
is not directly exposed on
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
移植 Python 代码
section of this document.
(Implementation by Brett Cannon)
改进模块
¶
abc
¶
Improved support for abstract base classes containing descriptors composed with abstract methods. The recommended approach to declaring abstract descriptors is now to provide
__isabstractmethod__
as a dynamically updated property. The built-in descriptors have been updated accordingly.
(Contributed by Darren Dale in
bpo-11610
)。
abc.ABCMeta.register()
now returns the registered subclass, which means it can now be used as a class decorator (
bpo-10868
).
array
¶
The
array
module supports the
long
long
type using
q
and
Q
type codes.
(Contributed by Oren Tirosh and Hirokazu Yamamoto in
bpo-1172711
)。
base64
¶
ASCII-only Unicode strings are now accepted by the decoding functions of the
base64
modern interface. For example,
base64.b64decode('YWJj')
返回
b'abc'
. (Contributed by Catalin Iacob in
bpo-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
bpo-13637
)。
bz2
¶
The
bz2
module has been rewritten from scratch. In the process, several new features have been added:
-
New
bz2.open()
function: open a bzip2-compressed file in binary or text mode.
-
bz2.BZ2File
can now read from and write to arbitrary file-like objects, by means of its constructor’s
fileobj
自变量。
(Contributed by Nadeem Vawda in
bpo-5863
)。
-
bz2.BZ2File
and
bz2.decompress()
can now decompress multi-stream inputs (such as those produced by the
pbzip2
tool).
bz2.BZ2File
can now also be used to create this type of file, using the
'a'
(append) mode.
(Contributed by Nir Aides in
bpo-1625
)。
-
bz2.BZ2File
now implements all of the
io.BufferedIOBase
API, except for the
detach()
and
truncate()
方法。
codecs
¶
The
mbcs
codec has been rewritten to handle correctly
replace
and
ignore
error handlers on all Windows versions. The
mbcs
codec now supports all error handlers, instead of only
replace
to encode and
ignore
以解码。
A new Windows-only codec has been added:
cp65001
(
bpo-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
命令)。
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.
(
bpo-12016
)
Incremental CJK codec encoders are no longer reset at each call to their encode() methods. For example:
>>> 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.
(
bpo-12100
)
The
unicode_internal
codec has been deprecated.
collections
¶
Addition of a new
ChainMap
class to allow treating a number of mappings as a single unit. (Written by Raymond Hettinger for
bpo-11089
, made public in
bpo-11297
)。
The abstract base classes have been moved in a new
collections.abc
module, to better differentiate between the abstract and the concrete collections classes. Aliases for ABCs are still present in the
collections
module to preserve existing imports. (
bpo-11085
)
The
Counter
class now supports the unary
+
and
-
operators, as well as the in-place operators
+=
,
-=
,
|=
，和
&=
. (Contributed by Raymond Hettinger in
bpo-13121
)。
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
threading
模块)。
(
bpo-13585
)
crypt
¶
Addition of salt and modular crypt format (hashing method) and the
mksalt()
function to the
crypt
模块。
(
bpo-10924
)
curses
¶
-
若
curses
module is linked to the ncursesw library, use Unicode functions when Unicode strings or characters are passed (e.g.
waddwstr()
), and bytes functions otherwise (e.g.
waddstr()
).
-
Use the locale encoding instead of
utf-8
to encode Unicode strings.
-
curses.window
拥有新的
curses.window.encoding
属性。
-
The
curses.window
class has a new
get_wch()
method to get a wide character
-
The
curses
module has a new
unget_wch()
function to push a wide character so the next
get_wch()
will return it
(Contributed by Iñigo Serna in
bpo-6755
)。
decimal
¶
-
bpo-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
https://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
|
特征
¶
-
The
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
HAVE_THREADS
被设为
False
.
API 变化
¶
-
The C module has the following context limits, depending on the machine architecture:
|
32 位
|
64-bit
|
|
MAX_PREC
|
425000000
|
999999999999999999
|
|
MAX_EMAX
|
425000000
|
999999999999999999
|
|
MIN_EMIN
|
-425000000
|
-999999999999999999
|
-
In the context templates (
DefaultContext
,
BasicContext
and
ExtendedContext
) the magnitude of
Emax
and
Emin
已变成
999999
.
-
The
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
InvalidOperation
is raised and the result is NaN. In the latter case it is always possible to use
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
exp()
and
ln()
functions, but the final result is only “almost always correctly rounded”.
-
In the C version, the context dictionary containing the signals is a
MutableMapping
. For speed reasons,
flags
and
traps
always refer to the same
MutableMapping
that the context was initialized with. If a new signal dictionary is assigned,
flags
and
traps
are updated with the new values, but they do not reference the RHS dictionary.
-
Pickling a
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
Context
constructor has been changed to match the order displayed by
repr()
.
-
The
watchexp
parameter in the
quantize()
方法被弃用。
email
¶
Policy Framework
¶
The email package now has a
policy
framework. A
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
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
parser
, or when a
Message
object is created, or when an email is serialized using a
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
compat32
.
The minimum set of controls implemented by all
policy
objects are:
|
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
对象的
defects
列表。
|
A new policy instance, with new settings, is created using the
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
或
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
.
ftplib
¶
-
ftplib.FTP
现在接受
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
bpo-8594
)。
-
The
FTP_TLS
class now provides a new
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
bpo-12139
)。
-
添加
ftplib.FTP.mlsd()
method which provides a parsable directory listing format and deprecates
ftplib.FTP.nlst()
and
ftplib.FTP.dir()
. (Contributed by Giampaolo Rodolà in
bpo-11072
)。
gc
¶
It is now possible to register callbacks invoked by the garbage collector before and after collection using the new
callbacks
列表。
hmac
¶
新的
compare_digest()
function has been added to prevent side channel attacks on digests through timing analysis. (Contributed by Nick Coghlan and Christian Heimes in
bpo-15061
)。
html
¶
html.parser.HTMLParser
is now able to parse broken markup without raising errors, therefore the
strict
argument of the constructor and the
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
bpo-15114
，和
bpo-14538
,
bpo-13993
,
bpo-13960
,
bpo-13358
,
bpo-1745761
,
bpo-755670
,
bpo-13357
,
bpo-12629
,
bpo-1200313
,
bpo-670664
,
bpo-13273
,
bpo-12888
,
bpo-7311
)。
新的
html5
dictionary that maps HTML5 named character references to the equivalent Unicode character(s) (e.g.
html5['gt;'] ==
'>'
) has been added to the
html.entities
module. The dictionary is now also used by
HTMLParser
. (Contributed by Ezio Melotti in
bpo-11113
and
bpo-15156
)。
imaplib
¶
The
IMAP4_SSL
constructor now accepts an SSLContext parameter to control parameters of the secure channel.
(Contributed by Sijin Joseph in
bpo-8808
)。
inspect
¶
新的
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
bpo-13062
)。
新的
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
bpo-15153
)。
io
¶
The
open()
function has a new
'x'
mode that can be used to exclusively create a new file, and raise a
FileExistsError
if the file already exists. It is based on the C11 ‘x’ mode to fopen().
(Contributed by David Townshend in
bpo-12760
)。
The constructor of the
TextIOWrapper
class has a new
write_through
optional argument. If
write_through
is
True
，调用
write()
are guaranteed not to be buffered: any data written on the
TextIOWrapper
object is immediately handled to its underlying binary buffer.
logging
¶
The
basicConfig()
function now supports an optional
handlers
argument taking an iterable of handlers to be added to the root logger.
A class level attribute
append_nul
has been added to
SysLogHandler
to allow control of the appending of the
NUL
(
\000
) byte to syslog records, since for some daemons it is required while for others it is passed through to the log.
math
¶
The
math
module has a new function,
log2()
, which returns the base-2 logarithm of
x
.
(Written by Mark Dickinson in
bpo-11888
)。
mmap
¶
The
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
bpo-12021
)。
nntplib
¶
The
nntplib.NNTP
class now supports the context management protocol to unconditionally consume
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
bpo-9795
)。
os
¶
-
The
os
module has a new
pipe2()
function that makes it possible to create a pipe with
O_CLOEXEC
or
O_NONBLOCK
flags set atomically. This is especially useful to avoid race conditions in multi-threaded programs.
-
The
os
module has a new
sendfile()
function which provides an efficient “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.
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
bpo-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 (
bpo-4761
,
bpo-10755
and
bpo-14626
).
-
The
os
module has a new
fwalk()
function similar to
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
(
相对于目录描述符的路径
) and/or
follow_symlinks
(
不遵循符号链接
):
access()
,
chflags()
,
chmod()
,
chown()
,
link()
,
lstat()
,
mkdir()
,
mkfifo()
,
mknod()
,
open()
,
readlink()
,
remove()
,
rename()
,
replace()
,
rmdir()
,
stat()
,
symlink()
,
unlink()
,
utime()
. Platform support for using these parameters can be checked via the sets
os.supports_dir_fd
and
os.supports_follows_symlinks
.
-
The following functions now support a file descriptor for their path argument:
chdir()
,
chmod()
,
chown()
,
execve()
,
listdir()
,
pathconf()
,
exists()
,
stat()
,
statvfs()
,
utime()
. Platform support for this can be checked via the
os.supports_fd
set.
-
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
supports_effective_ids
set.
-
The
os
module has two new functions:
getpriority()
and
setpriority()
. They can be used to get or set process niceness/priority in a fashion similar to
os.nice()
but extended to all processes instead of just the current one.
(Patch submitted by Giampaolo Rodolà in
bpo-10784
)。
-
新的
os.replace()
function allows cross-platform renaming of a file with overwriting the destination. With
os.rename()
, an existing destination file is overwritten under POSIX, but raises an error under Windows. (Contributed by Antoine Pitrou in
bpo-8828
)。
-
The stat family of functions (
stat()
,
fstat()
，和
lstat()
) now support reading a file’s timestamps with nanosecond precision. Symmetrically,
utime()
can now write file timestamps with nanosecond precision. (Contributed by Larry Hastings in
bpo-14127
)。
-
新的
os.get_terminal_size()
function queries the size of the terminal attached to a file descriptor. See also
shutil.get_terminal_size()
. (Contributed by Zbigniew Jędrzejewski-Szmek in
bpo-13609
)。
-
New functions to support Linux extended attributes (
bpo-12720
):
getxattr()
,
listxattr()
,
removexattr()
,
setxattr()
.
-
New interface to the scheduler. These functions control how a process is allocated CPU time by the operating system. New functions:
sched_get_priority_max()
,
sched_get_priority_min()
,
sched_getaffinity()
,
sched_getparam()
,
sched_getscheduler()
,
sched_rr_get_interval()
,
sched_setaffinity()
,
sched_setparam()
,
sched_setscheduler()
,
sched_yield()
,
-
New functions to control the file system:
-
posix_fadvise()
: Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations.
-
posix_fallocate()
: Ensures that enough disk space is allocated for a file.
-
sync()
: Force write of everything to disk.
-
Additional new posix functions:
-
lockf()
: Apply, test or remove a POSIX lock on an open file descriptor.
-
pread()
: Read from a file descriptor at an offset, the file offset remains unchanged.
-
pwrite()
: Write to a file descriptor from an offset, leaving the file offset unchanged.
-
readv()
: Read from a file descriptor into a number of writable buffers.
-
truncate()
: Truncate the file corresponding to
path
，因此最多
length
字节大小。
-
waitid()
: Wait for the completion of one or more child processes.
-
writev()
: Write the contents of
buffers
to a file descriptor, where
buffers
is an arbitrary sequence of buffers.
-
getgrouplist()
(
bpo-9344
): Return list of group ids that specified user belongs to.
-
times()
and
uname()
: Return type changed from a tuple to a tuple-like object with named attributes.
-
Some platforms now support additional constants for the
lseek()
function, such as
os.SEEK_HOLE
and
os.SEEK_DATA
.
-
New constants
RTLD_LAZY
,
RTLD_NOW
,
RTLD_GLOBAL
,
RTLD_LOCAL
,
RTLD_NODELETE
,
RTLD_NOLOAD
，和
RTLD_DEEPBIND
are available on platforms that support them. These are for use with the
sys.setdlopenflags()
function, and supersede the similar constants defined in
ctypes
and
DLFCN
. (Contributed by Victor Stinner in
bpo-13226
)。
-
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
bpo-14210
)
pydoc
¶
The Tk GUI and the
serve()
function have been removed from the
pydoc
模块：
pydoc -g
and
serve()
have been deprecated in Python 3.2.
re
¶
str
regular expressions now support
\u
and
\U
转义。
(Contributed by Serhiy Storchaka in
bpo-3665
)。
sched
¶
-
run()
现在接受
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
scheduler
in non-blocking applications. (Contributed by Giampaolo Rodolà in
bpo-13449
)。
-
scheduler
class can now be safely used in multi-threaded environments. (Contributed by Josiah Carlson and Giampaolo Rodolà in
bpo-8684
)。
-
timefunc
and
delayfunct
parameters of
scheduler
class constructor are now optional and defaults to
time.time()
and
time.sleep()
respectively. (Contributed by Chris Clark in
bpo-13245
)。
-
enter()
and
enterabs()
argument
parameter is now optional. (Contributed by Chris Clark in
bpo-13245
)。
-
enter()
and
enterabs()
now accept a
kwargs
parameter. (Contributed by Chris Clark in
bpo-13245
)。
select
¶
Solaris and derivative platforms have a new class
select.devpoll
for high performance asynchronous sockets via
/dev/poll
. (Contributed by Jesús Cea Avión in
bpo-6397
)。
shlex
¶
The previously undocumented helper function
quote
从
pipes
modules has been moved to the
shlex
module and documented.
quote()
properly escapes all characters in a string that might be otherwise given special meaning by the shell.
shutil
¶
-
New functions:
-
disk_usage()
: provides total, used and free disk space statistics. (Contributed by Giampaolo Rodolà in
bpo-12442
)。
-
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
bpo-12191
)。
-
shutil.get_terminal_size()
: returns the size of the terminal window to which the interpreter is attached. (Contributed by Zbigniew Jędrzejewski-Szmek in
bpo-13609
)。
-
copy2()
and
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
bpo-14127
and
bpo-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
bpo-12715
)。
-
When copying files to a different file system,
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
bpo-9993
)。
move()
now also returns the
dst
argument as its result.
-
rmtree()
is now resistant to symlink attacks on platforms which support the new
dir_fd
parameter in
os.open()
and
os.unlink()
. (Contributed by Martin von Löwis and Hynek Schlawack in
bpo-4489
)。
signal
¶
-
The
signal
module has new functions:
-
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.
-
signal.signal()
and
signal.siginterrupt()
raise an OSError, instead of a RuntimeError: OSError has an errno attribute.
smtpd
¶
The
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
命令。
(Initial
ELHO
support by Alberto Trevino. Size extension by Juhana Jauhiainen. Substantial additional work on the patch contributed by Michele Orrù and Dan Boswell.
bpo-8739
)
smtplib
¶
The
SMTP
,
SMTP_SSL
，和
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
bpo-11281
)。
SMTP
now supports the context management protocol, allowing an
SMTP
instance to be used in a
with
statement. (Contributed by Giampaolo Rodolà in
bpo-11289
)。
The
SMTP_SSL
constructor and the
starttls()
method now accept an SSLContext parameter to control parameters of the secure channel. (Contributed by Kasun Herath in
bpo-8809
)。
ssl
¶
-
The
ssl
module has two new random generation functions:
(Contributed by Victor Stinner in
bpo-12049
)。
-
The
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
bpo-11183
)。
-
load_cert_chain()
现在接受
password
argument to be used if the private key is encrypted. (Contributed by Adam Simpkins in
bpo-12803
)。
-
Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is now supported through the
load_dh_params()
and
set_ecdh_curve()
methods. (Contributed by Antoine Pitrou in
bpo-13626
and
bpo-13627
)。
-
SSL sockets have a new
get_channel_binding()
method allowing the implementation of certain authentication mechanisms such as SCRAM-SHA-1-PLUS. (Contributed by Jacek Konieczny in
bpo-12551
)。
-
You can query the SSL compression algorithm used by an SSL socket, thanks to its new
compression()
method. The new attribute
OP_NO_COMPRESSION
can be used to disable compression. (Contributed by Antoine Pitrou in
bpo-13634
)。
-
Support has been added for the Next Protocol Negotiation extension using the
ssl.SSLContext.set_npn_protocols()
method. (Contributed by Colin Marc in
bpo-14204
)。
-
SSL errors can now be introspected more easily thanks to
library
and
reason
attributes. (Contributed by Antoine Pitrou in
bpo-14837
)。
-
The
get_server_certificate()
function now supports IPv6. (Contributed by Charles-François Natali in
bpo-11811
)。
-
New attribute
OP_CIPHER_SERVER_PREFERENCE
allows setting SSLv3 server sockets to use the server’s cipher ordering preference rather than the client’s (
bpo-13635
).
stat
¶
The undocumented tarfile.filemode function has been moved to
stat.filemode()
. It can be used to convert a file’s mode to a string of the form ‘-rwxrwxrwx’.
(Contributed by Giampaolo Rodolà in
bpo-14807
)。
struct
¶
The
struct
module now supports
ssize_t
and
size_t
via the new codes
n
and
N
, respectively. (Contributed by Antoine Pitrou in
bpo-3163
)。
subprocess
¶
Command strings can now be bytes objects on posix platforms. (Contributed by Victor Stinner in
bpo-8513
)。
A new constant
DEVNULL
allows suppressing output in a platform-independent fashion. (Contributed by Ross Lagerwall in
bpo-5870
)。
tarfile
¶
tarfile
现在支持
lzma
encoding via the
lzma
module. (Contributed by Lars Gustäbel in
bpo-5689
)。
textwrap
¶
The
textwrap
module has a new
indent()
that makes it straightforward to add a common prefix to selected lines in a block of text (
bpo-13857
).
threading
¶
threading.Condition
,
threading.Semaphore
,
threading.BoundedSemaphore
,
threading.Event
，和
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
bpo-10968
)。
The
threading.Thread
constructor now accepts a
daemon
keyword argument to override the default behavior of inheriting the
daemon
flag value from the parent thread (
bpo-6064
).
The formerly private function
_thread.get_ident
is now available as the public function
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
time
模块：
-
get_clock_info()
: Get information on a clock.
-
monotonic()
: Monotonic clock (cannot go backward), not affected by system clock updates.
-
perf_counter()
: Performance counter with the highest available resolution to measure a short duration.
-
process_time()
: Sum of the system and user CPU time of the current process.
Other new functions:
To improve cross platform consistency,
sleep()
now raises a
ValueError
when passed a negative sleep value. Previously this was an error on posix, but produced an infinite sleep on Windows.
urllib
¶
The
Request
class, now accepts a
方法
argument used by
get_method()
to determine what HTTP method should be used. For example, this will send a
'HEAD'
请求：
>>> urlopen(Request('https://www.python.org', method='HEAD'))
(
bpo-1673007
)
webbrowser
¶
The
webbrowser
module supports more “browsers”: Google Chrome (named
chrome
,
chromium
,
chrome-browser
or
chromium-browser
depending on the version and operating system), and the generic launchers
xdg-open
, from the FreeDesktop.org project, and
gvfs-open
, which is the default URI handler for GNOME 3. (The former contributed by Arnaud Calmettes in
bpo-13620
, the latter by Matthias Klose in
bpo-14493
)。
xml.etree.ElementTree
¶
The
xml.etree.ElementTree
module now imports its C accelerator by default; there is no longer a need to explicitly import
xml.etree.cElementTree
(this module stays for backwards compatibility, but is now deprecated). In addition, the
iter
family of methods of
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
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
bpo-12646
)。
New attribute
zlib.ZLIB_RUNTIME_VERSION
reports the version string of the underlying
zlib
library that is loaded at runtime. (Contributed by Torsten Landschoff in
bpo-12306
)。
