Python 2.7.5官方文档：新特性和改进概览

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本资源是Python 2.7.5的官方文档，提供了对这一版本的全面概述和更新内容。文档涵盖了多个关键主题，旨在帮助用户了解Python语言的新特性、改进以及模块升级。以下是主要内容的详细解读： 1. **Python 2.x 的未来**：这部分介绍了Python 2.x系列的后续发展计划，可能会探讨为什么2.7.5是向Python 3.x过渡的重要步骤，以及对于仍在使用2.x版本用户的建议。 2. **Python 3.1 特性**：尽管是关于Python 3.1的介绍，但它可能在某些方面为Python 2.7.5的改进提供了背景，因为两个版本之间可能存在一定的继承关系或共通特性。 3. **PEPs（Python Enhancement Proposals）**：文档列出了几个重要的PEPs，如PEP 372引入了`collections.OrderedDict`，提供有序字典的功能；PEP 378提供了千位分隔符的格式化支持；PEP 389和391分别是`argparse`模块用于解析命令行参数和基于字典的日志配置，这些模块的改进提高了代码的可读性和实用性。 4. **语言变化**：这部分详述了Python 2.7.5中的语言级改进，包括解释器的变更和性能优化，有助于开发者理解新版本在核心语法和执行效率上的提升。 5. **新模块和升级**：文档提到的新模块如`importlib`、`sysconfig`、Tkinter（ttk模块的Themed Widgets）以及`unittest`和`ElementTree`的更新，展示了Python在标准库方面的扩展和增强。 6. **构建和C API**：这部分关注了构建工具和C API（Python C语言接口）的更改，对那些需要直接操作底层的开发者来说至关重要。 7. **平台特定的更改**：针对不同操作系统（Windows、MacOSX、FreeBSD等）的特殊优化，确保了跨平台兼容性。 8. **移植至Python 2.7**：指南帮助用户在迁移到Python 2.7.5时避免常见问题，提供了迁移策略和技术。 9. **致谢和索引**：最后，作者A.M.Kuchling表示感谢，并附有详细的索引，方便读者查找所需内容。这份文档是Python 2.7.5的权威指南，不仅适合初学者了解新功能，也对高级用户和开发者提供了深入的技术参考。通过学习和掌握其中的内容，用户可以更好地利用Python 2.7.5进行开发和维护工作。

...

NoOptionError: No option ’unknown’ in section: ’mysqld’

(Contributed by Mats Kindahl; issue 7005.)

• Deprecated function: contextlib.nested(), which allows handling more than one context manager

with a single with statement, has been deprecated, because the with statement now supports multiple

context managers.

• The cookielib module now ignores cookies that have an invalid version ﬁeld, one that doesn’t contain

an integer value. (Fixed by John J. Lee; issue 3924.)

• The copy module’s deepcopy() function will now correctly copy bound instance methods. (Imple-

mented by Robert Collins; issue 1515.)

• The ctypes module now always converts None to a C NULL pointer for arguments declared as pointers.

(Changed by Thomas Heller; issue 4606.) The underlying libfﬁ library has been updated to version 3.0.9,

containing various ﬁxes for different platforms. (Updated by Matthias Klose; issue 8142.)

• New method: the datetime module’s timedelta class gained a total_seconds() method that

returns the number of seconds in the duration. (Contributed by Brian Quinlan; issue 5788.)

• New method: the Decimal class gained a from_float() class method that performs an exact

conversion of a ﬂoating-point number to a Decimal. This exact conversion strives for the closest

decimal approximation to the ﬂoating-point representation’s value; the resulting decimal value will

therefore still include the inaccuracy, if any. For example, Decimal.from_float(0.1) returns

Decimal(’0.1000000000000000055511151231257827021181583404541015625’).

(Implemented by Raymond Hettinger; issue 4796.)

Comparing instances of Decimal with ﬂoating-point numbers now produces sensible results based on the

numeric values of the operands. Previously such comparisons would fall back to Python’s default rules for

comparing objects, which produced arbitrary results based on their type. Note that you still cannot combine

Decimal and ﬂoating-point in other operations such as addition, since you should be explicitly choosing

how to convert between ﬂoat and Decimal. (Fixed by Mark Dickinson; issue 2531.)

The constructor for Decimal now accepts ﬂoating-point numbers (added by Raymond Hettinger; issue

8257) and non-European Unicode characters such as Arabic-Indic digits (contributed by Mark Dickinson;

issue 6595).

Most of the methods of the Context class now accept integers as well as Decimal instances; the only

exceptions are the canonical() and is_canonical() methods. (Patch by Juan José Conti; issue

7633.)

When using Decimal instances with a string’s format() method, the default alignment was previ-

ously left-alignment. This has been changed to right-alignment, which is more sensible for numeric types.

(Changed by Mark Dickinson; issue 6857.)

Comparisons involving a signaling NaN value (or sNAN) now signal InvalidOperation instead of

silently returning a true or false value depending on the comparison operator. Quiet NaN values (or NaN)

are now hashable. (Fixed by Mark Dickinson; issue 7279.)

• The difflib module now produces output that is more compatible with modern diff/patch tools through

one small change, using a tab character instead of spaces as a separator in the header giving the ﬁlename.

(Fixed by Anatoly Techtonik; issue 7585.)

• The Distutils sdist command now always regenerates the MANIFEST ﬁle, since even if the

MANIFEST.in or setup.py ﬁles haven’t been modiﬁed, the user might have created some new ﬁles

that should be included. (Fixed by Tarek Ziadé; issue 8688.)

• The doctest module’s IGNORE_EXCEPTION_DETAIL ﬂag will now ignore the name of the module

containing the exception being tested. (Patch by Lennart Regebro; issue 7490.)

• The email module’s Message class will now accept a Unicode-valued payload, automatically converting

the payload to the encoding speciﬁed by output_charset. (Added by R. David Murray; issue 1368247.)

• The Fraction class now accepts a single ﬂoat or Decimal instance, or two rational numbers, as argu-

ments to its constructor. (Implemented by Mark Dickinson; rationals added in issue 5812, and ﬂoat/decimal

in issue 8294.)

Ordering comparisons (<, <=, >, >=) between fractions and complex numbers now raise a TypeError.

This ﬁxes an oversight, making the Fraction match the other numeric types.

• New class: FTP_TLS in the ftplib module provides secure FTP connections using TLS encapsulation of

authentication as well as subsequent control and data transfers. (Contributed by Giampaolo Rodola; issue

2054.)

The storbinary() method for binary uploads can now restart uploads thanks to an added rest parameter

(patch by Pablo Mouzo; issue 6845.)

• New class decorator: total_ordering() in the functools module takes a class that deﬁnes an

__eq__() method and one of __lt__(), __le__(), __gt__(), or __ge__(), and generates the

missing comparison methods. Since the __cmp__() method is being deprecated in Python 3.x, this deco-

rator makes it easier to deﬁne ordered classes. (Added by Raymond Hettinger; issue 5479.)

New function: cmp_to_key() will take an old-style comparison function that expects two arguments and

return a new callable that can be used as the key parameter to functions such as sorted(), min() and

max(), etc. The primary intended use is to help with making code compatible with Python 3.x. (Added by

Raymond Hettinger.)

• New function: the gc module’s is_tracked() returns true if a given instance is tracked by the garbage

collector, false otherwise. (Contributed by Antoine Pitrou; issue 4688.)

• The gzip module’s GzipFile now supports the context management protocol, so you can write with

gzip.GzipFile(...) as f: (contributed by Hagen Fürstenau; issue 3860), and it now implements

the io.BufferedIOBase ABC, so you can wrap it with io.BufferedReader for faster processing

(contributed by Nir Aides; issue 7471). It’s also now possible to override the modiﬁcation time recorded in

a gzipped ﬁle by providing an optional timestamp to the constructor. (Contributed by Jacques Frechet; issue

4272.)

Files in gzip format can be padded with trailing zero bytes; the gzip module will now consume these

trailing bytes. (Fixed by Tadek Pietraszek and Brian Curtin; issue 2846.)

• New attribute: the hashlib module now has an algorithms attribute containing a tuple nam-

ing the supported algorithms. In Python 2.7, hashlib.algorithms contains (’md5’, ’sha1’,

’sha224’, ’sha256’, ’sha384’, ’sha512’). (Contributed by Carl Chenet; issue 7418.)

• The default HTTPResponse class used by the httplib module now supports buffering, resulting in

much faster reading of HTTP responses. (Contributed by Kristján Valur Jónsson; issue 4879.)

The HTTPConnection and HTTPSConnection classes now support a source_address parameter, a

(host, port) 2-tuple giving the source address that will be used for the connection. (Contributed by

Eldon Ziegler; issue 3972.)

• The ihooks module now supports relative imports. Note that ihooks is an older module for customizing

imports, superseded by the imputil module added in Python 2.0. (Relative import support added by Neil

Schemenauer.)

• The imaplib module now supports IPv6 addresses. (Contributed by Derek Morr; issue 1655.)

• New function: the inspect module’s getcallargs() takes a callable and its positional and keyword

arguments, and ﬁgures out which of the callable’s parameters will receive each argument, returning a dic-

tionary mapping argument names to their values. For example:

>>> from inspect import getcallargs

>>> def f(a, b=1,

pos,

named):

... pass

>>> getcallargs(f, 1, 2, 3)

{’a’: 1, ’b’: 2, ’pos’: (3,), ’named’: {}}

>>> getcallargs(f, a=2, x=4)

{’a’: 2, ’b’: 1, ’pos’: (), ’named’: {’x’: 4}}

>>> getcallargs(f)

Traceback (most recent call last):

...

TypeError: f() takes at least 1 argument (0 given)

Contributed by George Sakkis; issue 3135.

• Updated module: The io library has been upgraded to the version shipped with Python 3.1. For 3.1, the

I/O library was entirely rewritten in C and is 2 to 20 times faster depending on the task being performed.

The original Python version was renamed to the _pyio module.

One minor resulting change: the io.TextIOBase class now has an errors attribute giving the error

setting used for encoding and decoding errors (one of ’strict’, ’replace’, ’ignore’).

The io.FileIO class now raises an OSError when passed an invalid ﬁle descriptor. (Implemented by

Benjamin Peterson; issue 4991.) The truncate() method now preserves the ﬁle position; previously it

would change the ﬁle position to the end of the new ﬁle. (Fixed by Pascal Chambon; issue 6939.)

• New function: itertools.compress(data, selectors) takes two iterators. Elements of data

are returned if the corresponding value in selectors is true:

itertools.compress(’ABCDEF’, [1,0,1,0,1,1]) =>

A, C, E, F

New function: itertools.combinations_with_replacement(iter, r) returns all the pos-

sible r-length combinations of elements from the iterable iter. Unlike combinations(), individual

elements can be repeated in the generated combinations:

itertools.combinations_with_replacement(’abc’, 2) =>

(’a’, ’a’), (’a’, ’b’), (’a’, ’c’),

(’b’, ’b’), (’b’, ’c’), (’c’, ’c’)

Note that elements are treated as unique depending on their position in the input, not their actual values.

The itertools.count() function now has a step argument that allows incrementing by values other

than 1. count() also now allows keyword arguments, and using non-integer values such as ﬂoats or

Decimal instances. (Implemented by Raymond Hettinger; issue 5032.)

itertools.combinations() and itertools.product() previously raised ValueError for

values of r larger than the input iterable. This was deemed a speciﬁcation error, so they now return an empty

iterator. (Fixed by Raymond Hettinger; issue 4816.)

• Updated module: The json module was upgraded to version 2.0.9 of the simplejson package, which

includes a C extension that makes encoding and decoding faster. (Contributed by Bob Ippolito; issue 4136.)

To support the new collections.OrderedDict type, json.load() now has an optional ob-

ject_pairs_hook parameter that will be called with any object literal that decodes to a list of pairs. (Con-

tributed by Raymond Hettinger; issue 5381.)

• The mailbox module’s Maildir class now records the timestamp on the directories it reads, and only

re-reads them if the modiﬁcation time has subsequently changed. This improves performance by avoiding

unneeded directory scans. (Fixed by A.M. Kuchling and Antoine Pitrou; issue 1607951, issue 6896.)

• New functions: the math module gained erf() and erfc() for the error function and the complemen-

tary error function, expm1() which computes e

x - 1 with more precision than using exp() and

subtracting 1, gamma() for the Gamma function, and lgamma() for the natural log of the Gamma func-

tion. (Contributed by Mark Dickinson and nirinA raseliarison; issue 3366.)

• The multiprocessing module’s Manager

classes can now be passed a callable that will be called

whenever a subprocess is started, along with a set of arguments that will be passed to the callable. (Con-

tributed by lekma; issue 5585.)

The Pool class, which controls a pool of worker processes, now has an optional maxtasksperchild param-

eter. Worker processes will perform the speciﬁed number of tasks and then exit, causing the Pool to start

a new worker. This is useful if tasks may leak memory or other resources, or if some tasks will cause the

worker to become very large. (Contributed by Charles Cazabon; issue 6963.)

• The nntplib module now supports IPv6 addresses. (Contributed by Derek Morr; issue 1664.)

• New functions: the os module wraps the following POSIX system calls: getresgid() and

getresuid(), which return the real, effective, and saved GIDs and UIDs; setresgid() and

setresuid(), which set real, effective, and saved GIDs and UIDs to new values; initgroups(),

which initialize the group access list for the current process. (GID/UID functions contributed by Travis H.;

issue 6508. Support for initgroups added by Jean-Paul Calderone; issue 7333.)

The os.fork() function now re-initializes the import lock in the child process; this ﬁxes problems on

Solaris when fork() is called from a thread. (Fixed by Zsolt Cserna; issue 7242.)

• In the os.path module, the normpath() and abspath() functions now preserve Unicode; if their

input path is a Unicode string, the return value is also a Unicode string. (normpath() ﬁxed by Matt

Giuca in issue 5827; abspath() ﬁxed by Ezio Melotti in issue 3426.)

• The pydoc module now has help for the various symbols that Python uses. You can now do help(’<<’)

or help(’@’), for example. (Contributed by David Laban; issue 4739.)

• The re module’s split(), sub(), and subn() now accept an optional ﬂags argument, for consistency

with the other functions in the module. (Added by Gregory P. Smith.)

• New function: run_path() in the runpy module will execute the code at a provided path argument.

path can be the path of a Python source ﬁle (example.py), a compiled bytecode ﬁle (example.pyc), a

directory (./package/), or a zip archive (example.zip). If a directory or zip path is provided, it will

be added to the front of sys.path and the module __main__ will be imported. It’s expected that the

directory or zip contains a __main__.py; if it doesn’t, some other __main__.py might be imported

from a location later in sys.path. This makes more of the machinery of runpy available to scripts that

want to mimic the way Python’s command line processes an explicit path name. (Added by Nick Coghlan;

issue 6816.)

• New function: in the shutil module, make_archive() takes a ﬁlename, archive type (zip or tar-

format), and a directory path, and creates an archive containing the directory’s contents. (Added by Tarek

Ziadé.)

shutil‘s copyfile() and copytree() functions now raise a SpecialFileError exception

when asked to copy a named pipe. Previously the code would treat named pipes like a regular ﬁle by

opening them for reading, and this would block indeﬁnitely. (Fixed by Antoine Pitrou; issue 3002.)

• The signal module no longer re-installs the signal handler unless this is truly necessary, which ﬁxes a

bug that could make it impossible to catch the EINTR signal robustly. (Fixed by Charles-Francois Natali;

issue 8354.)

• New functions: in the site module, three new functions return various site- and user-

speciﬁc paths. getsitepackages() returns a list containing all global site-packages direc-

tories, getusersitepackages() returns the path of the user’s site-packages directory, and

getuserbase() returns the value of the USER_BASE environment variable, giving the path to a di-

rectory that can be used to store data. (Contributed by Tarek Ziadé; issue 6693.)

The site module now reports exceptions occurring when the sitecustomize module is imported, and

will no longer catch and swallow the KeyboardInterrupt exception. (Fixed by Victor Stinner; issue

3137.)

• The create_connection() function gained a source_address parameter, a (host, port) 2-tuple

giving the source address that will be used for the connection. (Contributed by Eldon Ziegler; issue 3972.)

The recv_into() and recvfrom_into() methods will now write into objects that support the buffer

API, most usefully the bytearray and memoryview objects. (Implemented by Antoine Pitrou; issue

8104.)

• The SocketServer module’s TCPServer class now supports socket timeouts and disabling the Nagle

algorithm. The disable_nagle_algorithm class attribute defaults to False; if overridden to be True,

new request connections will have the TCP_NODELAY option set to prevent buffering many small sends

into a single TCP packet. The timeout class attribute can hold a timeout in seconds that will be applied

to the request socket; if no request is received within that time, handle_timeout() will be called and

handle_request() will return. (Contributed by Kristján Valur Jónsson; issue 6192 and issue 6267.)

• Updated module: the sqlite3 module has been updated to version 2.6.0 of the pysqlite package. Ver-

sion 2.6.0 includes a number of bugﬁxes, and adds the ability to load SQLite extensions from shared

libraries. Call the enable_load_extension(True) method to enable extensions, and then call

load_extension() to load a particular shared library. (Updated by Gerhard Häring.)

• The ssl module’s SSLSocket objects now support the buffer API, which ﬁxed a test suite failure (ﬁx

by Antoine Pitrou; issue 7133) and automatically set OpenSSL’s SSL_MODE_AUTO_RETRY, which will

prevent an error code being returned from recv() operations that trigger an SSL renegotiation (ﬁx by

Antoine Pitrou; issue 8222).

The ssl.wrap_socket() constructor function now takes a ciphers argument that’s a string listing the

encryption algorithms to be allowed; the format of the string is described in the OpenSSL documentation.

(Added by Antoine Pitrou; issue 8322.)

Another change makes the extension load all of OpenSSL’s ciphers and digest algorithms so that they’re all

available. Some SSL certiﬁcates couldn’t be veriﬁed, reporting an “unknown algorithm” error. (Reported

by Beda Kosata, and ﬁxed by Antoine Pitrou; issue 8484.)

The version of OpenSSL being used is now available as the module attributes ssl.OPENSSL_VERSION

(a string), ssl.OPENSSL_VERSION_INFO (a 5-tuple), and ssl.OPENSSL_VERSION_NUMBER (an

integer). (Added by Antoine Pitrou; issue 8321.)

• The struct module will no longer silently ignore overﬂow errors when a value is too large for a particular

integer format code (one of bBhHiIlLqQ); it now always raises a struct.error exception. (Changed

by Mark Dickinson; issue 1523.) The pack() function will also attempt to use __index__() to convert

and pack non-integers before trying the __int__() method or reporting an error. (Changed by Mark

Dickinson; issue 8300.)

• New function: the subprocess module’s check_output() runs a command with a speciﬁed set of

arguments and returns the command’s output as a string when the command runs without error, or raises a

CalledProcessError exception otherwise.

>>> subprocess.check_output([’df’, ’-h’, ’.’])

’Filesystem Size Used Avail Capacity Mounted on\n

/dev/disk0s2 52G 49G 3.0G 94% /\n’

>>> subprocess.check_output([’df’, ’-h’, ’/bogus’])

...

subprocess.CalledProcessError: Command ’[’df’, ’-h’, ’/bogus’]’ returned non-zero exit status 1

(Contributed by Gregory P. Smith.)

The subprocess module will now retry its internal system calls on receiving an EINTR signal. (Reported

by several people; ﬁnal patch by Gregory P. Smith in issue 1068268.)

• New function: is_declared_global() in the symtable module returns true for variables that are

explicitly declared to be global, false for ones that are implicitly global. (Contributed by Jeremy Hylton.)

• The syslog module will now use the value of sys.argv[0] as the identiﬁer instead of the previous

default value of ’python’. (Changed by Sean Reifschneider; issue 8451.)

• The sys.version_info value is now a named tuple, with attributes named major, minor, micro,

releaselevel, and serial. (Contributed by Ross Light; issue 4285.)

sys.getwindowsversion() also returns a named tuple, with attributes named major,

minor, build, platform, service_pack, service_pack_major, service_pack_minor,

suite_mask, and product_type. (Contributed by Brian Curtin; issue 7766.)

• The tarfile module’s default error handling has changed, to no longer suppress fatal errors. The default

error level was previously 0, which meant that errors would only result in a message being written to the

debug log, but because the debug log is not activated by default, these errors go unnoticed. The default error

level is now 1, which raises an exception if there’s an error. (Changed by Lars Gustäbel; issue 7357.)

tarfile now supports ﬁltering the TarInfo objects being added to a tar ﬁle. When you call add(), you

may supply an optional ﬁlter argument that’s a callable. The ﬁlter callable will be passed the TarInfo for

every ﬁle being added, and can modify and return it. If the callable returns None, the ﬁle will be excluded

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Python 2.7.5官方文档：新特性和改进概览

Python 2.7.5 Documentation

python-2.7.5 CentOS、redhat可安装

python-2.7.5安装包

centos7安装python2.7.5

yum 安装python2.7.5

python-2.7.5-90.el7.x86_64.rpm

linux安装python2.7.5

centos7安装OpenStack-Glance时报错 Requires:python=2.7.5-90，el7

centos7安装python=2.7.5-90.el7的具体命令是什么

centos上安装python2.7.5安装包

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