What’s New In Python 3.7¶
Release: | 3.7.0a1 |
---|---|
Date: | October 04, 2017 |
本文解释了Python 3.7中的新功能,与3.6相比。
有关完整的详细信息,请参阅更新日志。
Note
用户应该知道,该文档目前正在草拟中。 随着Python 3.7的发布,它将被大幅更新,因此即使在阅读了早期版本之后,它仍然值得检查。
总结 – 发行亮点¶
新特点¶
PEP 538: 遗留的C语言环境限制¶
在Python 3系列中正在进行的一个挑战是确定一种合理的默认策略,用于处理当前在非windows平台上使用缺省C语言环境所隐含的“7位ASCII”文本编码假设。
PEP 538 updates the default interpreter command line interface to
automatically coerce that locale to an available UTF-8 based locale as
described in the documentation of the new PYTHONCOERCECLOCALE
environment variable. Automatically setting LC_CTYPE
this way means that
both the core interpreter and locale-aware C extensions (such as
readline
) will assume the use of UTF-8 as the default text encoding,
rather than ASCII.
The platform support definition in PEP 11 has also been updated to limit full text handling support to suitably configured non-ASCII based locales.
As part of this change, the default error handler for stdin
and stdout
is now surrogateescape
(rather than strict
) when using any of the
defined coercion target locales (currently C.UTF-8
, C.utf8
, and
UTF-8
). The default error handler for stderr
continues to be
backslashreplace
, regardless of locale.
Locale coercion is silent by default, but to assist in debugging potentially
locale related integration problems, explicit warnings (emitted directly on
stderr
can be requested by setting PYTHONCOERCECLOCALE=warn
. This
setting will also cause the Python runtime to emit a warning if the legacy C
locale remains active when the core interpreter is initialized.
See also
- PEP 538 – Coercing the legacy C locale to a UTF-8 based locale
- PEP written and implemented by Nick Coghlan.
Other Language Changes¶
- More than 255 arguments can now be passed to a function, and a function can now have more than 255 parameters. (Contributed by Serhiy Storchaka in bpo-12844 and bpo-18896.)
bytes.fromhex()
andbytearray.fromhex()
now ignore all ASCII whitespace, not only spaces. (Contributed by Robert Xiao in bpo-28927.)ImportError
now displays module name and module__file__
path whenfrom ... import ...
fails. (Contributed by Matthias Bussonnier in bpo-29546.)- Circular imports involving absolute imports with binding a submodule to a name are now supported. (Contributed by Serhiy Storchaka in bpo-30024.)
object.__format__(x, '')
is now equivalent tostr(x)
rather thanformat(str(self), '')
. (Contributed by Serhiy Storchaka in bpo-28974.)
New Modules¶
- None yet.
Improved Modules¶
argparse¶
The parse_intermixed_args()
supports letting
the user intermix options and positional arguments on the command line,
as is possible in many unix commands. It supports most but not all
argparse features. (Contributed by paul.j3 in bpo-14191.)
binascii¶
The b2a_uu()
function now accepts an optional backtick
keyword argument. When it’s true, zeros are represented by '`'
instead of spaces. (Contributed by Xiang Zhang in bpo-30103.)
calendar¶
The class HTMLCalendar
has new class attributes which ease
the customisation of the CSS classes in the produced HTML calendar.
(Contributed by Oz Tiram in bpo-30095.)
cgi¶
parse_multipart()
returns the same results as
FieldStorage
: for non-file fields, the value associated to a key
is a list of strings, not bytes.
(Contributed by Pierre Quentel in bpo-29979.)
contextlib¶
contextlib.asynccontextmanager()
has been added. (Contributed by
Jelle Zijlstra in bpo-29679.)
dis¶
The dis()
function now is able to
disassemble nested code objects (the code of comprehensions, generator
expressions and nested functions, and the code used for building nested
classes). (Contributed by Serhiy Storchaka in bpo-11822.)
distutils¶
README.rst is now included in the list of distutils standard READMEs and therefore included in source distributions. (Contributed by Ryan Gonzalez in bpo-11913.)
http.server¶
SimpleHTTPRequestHandler
supports the HTTP
If-Modified-Since header. The server returns the 304 response status if the
target file was not modified after the time specified in the header.
(Contributed by Pierre Quentel in bpo-29654.)
Add the parameter directory
to the SimpleHTTPRequestHandler
and the --directory
to the command line of the module server
.
With this parameter, the server serves the specified directory, by default it uses the current working directory.
(Contributed by Stéphane Wirtel and Julien Palard in bpo-28707.)
locale¶
Added another argument monetary in format_string()
of locale
.
If monetary is true, the conversion uses monetary thousands separator and
grouping strings. (Contributed by Garvit in bpo-10379.)
math¶
New remainder()
function, implementing the IEEE 754-style remainder
operation. (Contributed by Mark Dickinson in bpo-29962.)
os¶
Added support for bytes
paths in fwalk()
. (Contributed by
Serhiy Storchaka in bpo-28682.)
Added support for file descriptors in scandir()
on Unix. (Contributed by Serhiy Storchaka in bpo-25996.)
New function os.register_at_fork()
allows registering Python callbacks
to be executed on a process fork. (Contributed by Antoine Pitrou in
bpo-16500.)
pdb¶
set_trace()
now takes an optional header
keyword-only
argument. If given, this is printed to the console just before debugging
begins.
string¶
string.Template
now lets you to optionally modify the regular
expression pattern for braced placeholders and non-braced placeholders
separately. (Contributed by Barry Warsaw in bpo-1198569.)
unittest.mock¶
The sentinel
attributes now preserve their identity
when they are copied
or pickled
. (Contributed by
Serhiy Storchaka in bpo-20804.)
xmlrpc.server¶
register_function()
of xmlrpc.server.SimpleXMLRPCDispatcher
and
its subclasses can be used as a decorator. (Contributed by Xiang Zhang in
bpo-7769.)
unicodedata¶
The internal unicodedata
database has been upgraded to use Unicode 10. (Contributed by Benjamin
Peterson.)
urllib.parse¶
urllib.parse.quote()
has been updated from RFC 2396 to RFC 3986,
adding ~ to the set of characters that is never quoted by default.
(Contributed by Christian Theune and Ratnadeep Debnath in bpo-16285.)
uu¶
Function encode()
now accepts an optional backtick
keyword argument. When it’s true, zeros are represented by '`'
instead of spaces. (Contributed by Xiang Zhang in bpo-30103.)
xml.etree¶
ElementPath predicates in the find()
methods can now compare text of the current node with [. = "text"]
,
not only text in children. Predicates also allow adding spaces for
better readability. (Contributed by Stefan Behnel in bpo-31648.)
zipapp¶
Function zipapp.create_archive()
now accepts an optional filter
argument to allow the user to select which files should be included in the
archive, and an optional compressed argument to generate a compressed
archive.
A command line option --compress
has also been added to support
compression.
Optimizations¶
- Added two new opcodes:
LOAD_METHOD
andCALL_METHOD
to avoid instantiation of bound method objects for method calls, which results in method calls being faster up to 20%. (Contributed by Yury Selivanov and INADA Naoki in bpo-26110.) - Searching some unlucky Unicode characters (like Ukrainian capital “Є”) in a string was to 25 times slower than searching other characters. Now it is slower only by 3 times in worst case. (Contributed by Serhiy Storchaka in bpo-24821.)
- Fast implementation from standard C library is now used for functions
erf()
anderfc()
in themath
module. (Contributed by Serhiy Storchaka in bpo-26121.) - The
os.fwalk()
function has been sped up by 2 times. This was done using theos.scandir()
function. (Contributed by Serhiy Storchaka in bpo-25996.) - Optimized case-insensitive matching and searching of
regular expressions
. Searching some patterns can now be up to 20 times faster. (Contributed by Serhiy Storchaka in bpo-30285.) selectors.EpollSelector.modify()
,selectors.PollSelector.modify()
andselectors.DevpollSelector.modify()
may be around 10% faster under heavy loads. (Contributed by Giampaolo Rodola’ in bpo-30014)
Build and C API Changes¶
- A full copy of libffi is no longer bundled for use when building the
_ctypes
module on non-OSX UNIX platforms. An installed copy of libffi is now required when building_ctypes
on such platforms. Contributed by Zachary Ware in bpo-27979. - The fields
name
anddoc
of structuresPyMemberDef
,PyGetSetDef
,PyStructSequence_Field
,PyStructSequence_Desc
, andwrapperbase
are now of typeconst char *
rather ofchar *
. (Contributed by Serhiy Storchaka in bpo-28761.) - The result of
PyUnicode_AsUTF8AndSize()
andPyUnicode_AsUTF8()
is now of typeconst char *
rather ofchar *
. (Contributed by Serhiy Storchaka in bpo-28769.) - Added functions
PySlice_Unpack()
andPySlice_AdjustIndices()
. (Contributed by Serhiy Storchaka in bpo-27867.) PyOS_AfterFork()
is deprecated in favour of the new functionsPyOS_BeforeFork()
,PyOS_AfterFork_Parent()
andPyOS_AfterFork_Child()
. (Contributed by Antoine Pitrou in bpo-16500.)- The Windows build process no longer depends on Subversion to pull in external
sources, a Python script is used to download zipfiles from GitHub instead.
If Python 3.6 is not found on the system (via
py -3.6
), NuGet is used to download a copy of 32-bit Python for this purpose. (Contributed by Zachary Ware in bpo-30450.) - Support for building
--without-threads
is removed. (Contributed by Antoine Pitrou in bpo-31370.).
Other CPython Implementation Changes¶
- Trace hooks may now opt out of receiving
line
events from the interpreter by setting the newf_trace_lines
attribute toFalse
on the frame being traced. (Contributed by Nick Coghlan in bpo-31344.) - Trace hooks may now opt in to receiving
opcode
events from the interpreter by setting the newf_trace_opcodes
attribute toTrue
on the frame being traced. (Contributed by Nick Coghlan in bpo-31344.)
Deprecated¶
- Function
PySlice_GetIndicesEx()
is deprecated and replaced with a macro ifPy_LIMITED_API
is not set or set to the value between0x03050400
and0x03060000
(not including) or0x03060100
or higher. (Contributed by Serhiy Storchaka in bpo-27867.) - Deprecated
format()
fromlocale
, use theformat_string()
instead. (Contributed by Garvit in bpo-10379.) - Methods
MetaPathFinder.find_module()
(replaced byMetaPathFinder.find_spec()
) andPathEntryFinder.find_loader()
(replaced byPathEntryFinder.find_spec()
) both deprecated in Python 3.4 now emitDeprecationWarning
. (Contributed by Matthias Bussonnier in bpo-29576) - Using non-integer value for selecting a plural form in
gettext
is now deprecated. It never correctly worked. (Contributed by Serhiy Storchaka in bpo-28692.) - The
macpath
is now deprecated and will be removed in Python 3.8.
Changes in the C API¶
- The type of results of
PyThread_start_new_thread()
andPyThread_get_thread_ident()
, and the id parameter ofPyThreadState_SetAsyncExc()
changed fromlong
tounsigned long
. (Contributed by Serhiy Storchaka in bpo-6532.) PyUnicode_AsWideCharString()
now raises aValueError
if the second argument is NULL and thewchar_t*
string contains null characters. (Contributed by Serhiy Storchaka in bpo-30708.)
Windows Only¶
- The python launcher, (py.exe), can accept 32 & 64 bit specifiers without
having to specify a minor version as well. So
py -3-32
andpy -3-64
become valid as well aspy -3.7-32
, also the -m-64 and -m.n-64 forms are now accepted to force 64 bit python even if 32 bit would have otherwise been used. If the specified version is not available py.exe will error exit. (Contributed by Steve Barnes in bpo-30291.) - The launcher can be run as “py -0” to produce a list of the installed pythons, with default marked with an asterix. Running “py -0p” will include the paths. If py is run with a version specifier that cannot be matched it will also print the short form list of available specifiers. (Contributed by Steve Barnes in bpo-30362.)
Removed¶
API and Feature Removals¶
- Unknown escapes consisting of
'\'
and an ASCII letter in replacement templates forre.sub()
were deprecated in Python 3.5, and will now cause an error. - Removed support of the exclude argument in
tarfile.TarFile.add()
. It was deprecated in Python 2.7 and 3.2. Use the filter argument instead. - The
splitunc()
function in thentpath
module was deprecated in Python 3.1, and has now been removed. Use thesplitdrive()
function instead. collections.namedtuple()
no longer supports the verbose parameter or_source
attribute which showed the generated source code for the named tuple class. This was part of an optimization designed to speed-up class creation. (Contributed by Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger in bpo-28638.)- Functions
bool()
,float()
,list()
andtuple()
no longer take keyword arguments. The first argument ofint()
can now be passed only as positional argument. - Removed previously deprecated in Python 2.4 classes
Plist
,Dict
and_InternalDict
in theplistlib
module. Dict values in the result of functionsreadPlist()
andreadPlistFromBytes()
are now normal dicts. You no longer can use attribute access to access items of these dictionaries.
Porting to Python 3.7¶
This section lists previously described changes and other bugfixes that may require changes to your code.
Changes in the Python API¶
pkgutil.walk_packages()
now raises ValueError if path is a string. Previously an empty list was returned. (Contributed by Sanyam Khurana in bpo-24744.)- A format string argument for
string.Formatter.format()
is now positional-only. Passing it as a keyword argument was deprecated in Python 3.5. (Contributed by Serhiy Storchaka in bpo-29193.) - Attributes
key
,value
andcoded_value
of classhttp.cookies.Morsel
are now read-only. Assigning to them was deprecated in Python 3.5. Use theset()
method for setting them. (Contributed by Serhiy Storchaka in bpo-29192.) Module
,FunctionDef
,AsyncFunctionDef
, andClassDef
AST nodes now have a newdocstring
field. The first statement in their body is not considered as a docstring anymore.co_firstlineno
andco_lnotab
of code object for class and module are affected by this change. (Contributed by INADA Naoki and Eugene Toder in bpo-29463.)- The mode argument of
os.makedirs()
no longer affects the file permission bits of newly-created intermediate-level directories. To set their file permission bits you can set the umask before invokingmakedirs()
. (Contributed by Serhiy Storchaka in bpo-19930.) - The
struct.Struct.format
type is nowstr
instead ofbytes
. (Contributed by Victor Stinner in bpo-21071.) - Due to internal changes in
socket
you won’t be able tosocket.fromshare()
a socketshare()
-ed in older Python versions. repr
fordatetime.timedelta
has changed to include keyword arguments in the output. (Contributed by Utkarsh Upadhyay in bpo-30302.)
CPython bytecode changes¶
- Added two new opcodes:
LOAD_METHOD
andCALL_METHOD
. (Contributed by Yury Selivanov and INADA Naoki in bpo-26110.)