Python2.7有什么新变化

新增和改进的模块¶

As in every release, Python's standard library received a number of

enhancements and bug fixes. Here's a partial list of the most notable

changes, sorted alphabetically by module name. Consult the

Misc/NEWS file in the source tree for a more complete list of

changes, or look through the Subversion logs for all the details.

• The bdb module's base debugging class Bdb

  gained a feature for skipping modules. The constructor

  now takes an iterable containing glob-style patterns such as

  django.*; the debugger will not step into stack frames

  from a module that matches one of these patterns.

  (Contributed by Maru Newby after a suggestion by

  Senthil Kumaran; bpo-5142.)

• The binascii module now supports the buffer API, so it can be

  used with memoryview instances and other similar buffer objects.

  (Backported from 3.x by Florent Xicluna; bpo-7703.)

• Updated module: the bsddb module has been updated from 4.7.2devel9

  to version 4.8.4 of

  the pybsddb package.

  The new version features better Python 3.x compatibility, various bug fixes,

  and adds several new BerkeleyDB flags and methods.

  (Updated by Jesús Cea Avión; bpo-8156. The pybsddb

  changelog can be read at http://hg.jcea.es/pybsddb/file/tip/ChangeLog.)

• The bz2 module's BZ2File now supports the context

  management protocol, so you can write withbz2.BZ2File(...)asf:.

  (Contributed by Hagen Fürstenau; bpo-3860.)

• New class: the Counter class in the collections

  module is useful for tallying data. Counter instances

  behave mostly like dictionaries but return zero for missing keys instead of

  raising a KeyError:

  >>> fromcollectionsimportCounter
  >>> c=Counter()
  >>> forletterin'here is a sample of english text':
  ... c[letter]+=1
  ...
  >>> c
  Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
  'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
  'p': 1, 'r': 1, 'x': 1})
  >>> c['e']
  5
  >>> c['z']
  0
  

  There are three additional Counter methods.

  most_common() returns the N most common

  elements and their counts. elements()

  returns an iterator over the contained elements, repeating each

  element as many times as its count.

  subtract() takes an iterable and

  subtracts one for each element instead of adding; if the argument is

  a dictionary or another Counter, the counts are

  subtracted.

  >>> c.most_common(5)
  [(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
  >>> c.elements()->
     'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
     'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
     'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
     's', 's', 'r', 't', 't', 'x'
  >>> c['e']
  5
  >>> c.subtract('very heavy on the letter e')
  >>> c['e']# Count is now lower
  -1
  

  Contributed by Raymond Hettinger; bpo-1696199.

  New class: OrderedDict is described in the earlier

  section PEP 372: Adding an Ordered Dictionary to collections.

  New method: The deque data type now has a

  count() method that returns the number of

  contained elements equal to the supplied argument x, and a

  reverse() method that reverses the elements

  of the deque in-place. deque also exposes its maximum

  length as the read-only maxlen attribute.

  (Both features added by Raymond Hettinger.)

  The namedtuple class now has an optional rename parameter.

  If rename is true, field names that are invalid because they've

  been repeated or aren't legal Python identifiers will be

  renamed to legal names that are derived from the field's

  position within the list of fields:

  >>> fromcollectionsimportnamedtuple
  >>> T=namedtuple('T',['field1','$illegal','for','field2'],rename=True)
  >>> T._fields
  ('field1', '_1', '_2', 'field2')
  

  (Added by Raymond Hettinger; bpo-1818.)

  Finally, the Mapping abstract base class now

  returns NotImplemented if a mapping is compared to

  another type that isn't a Mapping.

  (Fixed by Daniel Stutzbach; bpo-8729.)

• Constructors for the parsing classes in the ConfigParser module now

  take an allow_no_value parameter, defaulting to false; if true,

  options without values will be allowed. For example:

  >>> importConfigParser,StringIO
  >>> sample_config="""
  ... [mysqld]
  ... user = mysql
  ... pid-file = /var/run/mysqld/mysqld.pid
  ... skip-bdb
  ... """
  >>> config=ConfigParser.RawConfigParser(allow_no_value=True)
  >>> config.readfp(StringIO.StringIO(sample_config))
  >>> config.get('mysqld','user')
  'mysql'
  >>> printconfig.get('mysqld','skip-bdb')
  None
  >>> printconfig.get('mysqld','unknown')
  Traceback (most recent call last):
  ...
  NoOptionError: No option 'unknown' in section: 'mysqld'
  

  (Contributed by Mats Kindahl; bpo-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; bpo-3924.)

• The copy module's deepcopy() function will now

  correctly copy bound instance methods. (Implemented by

  Robert Collins; bpo-1515.)

• The ctypes module now always converts None to a C NULL

  pointer for arguments declared as pointers. (Changed by Thomas

  Heller; bpo-4606.) The underlying libffi library has been updated to version

  3.0.9, containing various fixes for different platforms. (Updated

  by Matthias Klose; bpo-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; bpo-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; bpo-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; bpo-2531.)

  The constructor for Decimal now accepts

  floating-point numbers (added by Raymond Hettinger; bpo-8257)

  and non-European Unicode characters such as Arabic-Indic digits

  (contributed by Mark Dickinson; bpo-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; bpo-7633.)

  When using Decimal instances with a string's

  format() method, the default alignment was previously

  left-alignment. This has been changed to right-alignment, which is

  more sensible for numeric types. (Changed by Mark Dickinson; bpo-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;

  bpo-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; bpo-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; bpo-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; bpo-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; bpo-1368247.)

• The Fraction class now accepts a single float or

  Decimal instance, or two rational numbers, as

  arguments to its constructor. (Implemented by Mark Dickinson;

  rationals added in bpo-5812, and float/decimal in

  bpo-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; bpo-2054.)

  The storbinary() method for binary uploads can now restart

  uploads thanks to an added rest parameter (patch by Pablo Mouzo;

  bpo-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 decorator makes it easier to define ordered classes.

  (Added by Raymond Hettinger; bpo-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; bpo-4688.)

• The gzip module's GzipFile now supports the context

  management protocol, so you can write withgzip.GzipFile(...)asf:

  (contributed by Hagen Fürstenau; bpo-3860), and it now implements

  the io.BufferedIOBase ABC, so you can wrap it with

  io.BufferedReader for faster processing

  (contributed by Nir Aides; bpo-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; bpo-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; bpo-2846.)

• New attribute: the hashlib module now has an algorithms

  attribute containing a tuple naming the supported algorithms.

  In Python 2.7, hashlib.algorithms contains

  ('md5','sha1','sha224','sha256','sha384','sha512').

  (Contributed by Carl Chenet; bpo-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; bpo-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; bpo-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; bpo-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 dictionary mapping argument names to their values. For example:

  >>> frominspectimportgetcallargs
  >>> deff(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)
  

  （由 Georg Sakkis 在 bpo-3135 中贡献）

• 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;

  bpo-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; bpo-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 possible 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; bpo-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; bpo-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; bpo-4136.)

  To support the new collections.OrderedDict type, json.load()

  now has an optional object_pairs_hook parameter that will be called

  with any object literal that decodes to a list of pairs.

  (Contributed by Raymond Hettinger; bpo-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; bpo-1607951, bpo-6896.)

• New functions: the math module gained

  erf() and erfc() for the error function and the complementary 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 function.

  (Contributed by Mark Dickinson and nirinA raseliarison; bpo-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.

  (Contributed by lekma; bpo-5585.)

  The Pool class, which controls a pool of worker processes,

  now has an optional maxtasksperchild parameter. 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; bpo-6963.)

• The nntplib module now supports IPv6 addresses.

  (Contributed by Derek Morr; bpo-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.; bpo-6508. Support for initgroups added

  by Jean-Paul Calderone; bpo-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; bpo-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 bpo-5827;

  abspath() fixed by Ezio Melotti in bpo-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; bpo-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; bpo-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; bpo-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; bpo-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 directories,

  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 directory that can be used

  to store data.

  (Contributed by Tarek Ziadé; bpo-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; bpo-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; bpo-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; bpo-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; bpo-6192 and bpo-6267.)

• Updated module: the sqlite3 module has been updated to

  version 2.6.0 of the pysqlite package. Version 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;

  bpo-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; bpo-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; bpo-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;

  bpo-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; bpo-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;

  bpo-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; bpo-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
  

  （由 Gregory P. Smith 贡献）

  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 bpo-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; bpo-8451.)

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

  named major, minor, micro,

  releaselevel, and serial. (Contributed by Ross

  Light; bpo-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; bpo-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; bpo-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 from the

  resulting archive. This is more powerful than the existing

  exclude argument, which has therefore been deprecated.

  (Added by Lars Gustäbel; bpo-6856.)

  The TarFile class also now supports the context management protocol.

  (Added by Lars Gustäbel; bpo-7232.)

• The wait() method of the threading.Event class

  now returns the internal flag on exit. This means the method will usually

  return true because wait() is supposed to block until the

  internal flag becomes true. The return value will only be false if

  a timeout was provided and the operation timed out.

  (Contributed by Tim Lesher; bpo-1674032.)

• The Unicode database provided by the unicodedata module is

  now used internally to determine which characters are numeric,

  whitespace, or represent line breaks. The database also

  includes information from the Unihan.txt data file (patch

  by Anders Chrigström and Amaury Forgeot d'Arc; bpo-1571184)

  and has been updated to version 5.2.0 (updated by

  Florent Xicluna; bpo-8024).

• The urlparse module's urlsplit() now handles

  unknown URL schemes in a fashion compliant with RFC 3986: if the

  URL is of the form "<something>://...", the text before the

  :// is treated as the scheme, even if it's a made-up scheme that

  the module doesn't know about. This change may break code that

  worked around the old behaviour. For example, Python 2.6.4 or 2.5

  will return the following:

  >>> importurlparse
  >>> urlparse.urlsplit('invented://host/filename?query')
  ('invented', '', '//host/filename?query', '', '')
  

  Python 2.7 (and Python 2.6.5) will return:

  >>> importurlparse
  >>> urlparse.urlsplit('invented://host/filename?query')
  ('invented', 'host', '/filename?query', '', '')
  

  (Python 2.7 actually produces slightly different output, since it

  returns a named tuple instead of a standard tuple.)

  The urlparse module also supports IPv6 literal addresses as defined by

  RFC 2732 (contributed by Senthil Kumaran; bpo-2987).

  >>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo')
  ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]',
              path='/foo', params='', query='', fragment='')
  

• New class: the WeakSet class in the weakref

  module is a set that only holds weak references to its elements; elements

  will be removed once there are no references pointing to them.

  (Originally implemented in Python 3.x by Raymond Hettinger, and backported

  to 2.7 by Michael Foord.)

• The ElementTree library, xml.etree, no longer escapes

  ampersands and angle brackets when outputting an XML processing

  instruction (which looks like <?xml-stylesheethref="#style1"?>)

  or comment (which looks like <!--comment-->).

  (Patch by Neil Muller; bpo-2746.)

• The XML-RPC client and server, provided by the xmlrpclib and

  SimpleXMLRPCServer modules, have improved performance by

  supporting HTTP/1.1 keep-alive and by optionally using gzip encoding

  to compress the XML being exchanged. The gzip compression is

  controlled by the encode_threshold attribute of

  SimpleXMLRPCRequestHandler, which contains a size in bytes;

  responses larger than this will be compressed.

  (Contributed by Kristján Valur Jónsson; bpo-6267.)

• The zipfile module's ZipFile now supports the context

  management protocol, so you can write withzipfile.ZipFile(...)asf:.

  (Contributed by Brian Curtin; bpo-5511.)

  zipfile now also supports archiving empty directories and

  extracts them correctly. (Fixed by Kuba Wieczorek; bpo-4710.)

  Reading files out of an archive is faster, and interleaving

  read() and readline() now works correctly.

  (Contributed by Nir Aides; bpo-7610.)

  The is_zipfile() function now

  accepts a file object, in addition to the path names accepted in earlier

  versions. (Contributed by Gabriel Genellina; bpo-4756.)

  The writestr() method now has an optional compress_type parameter

  that lets you override the default compression method specified in the

  ZipFile constructor. (Contributed by Ronald Oussoren;

  bpo-6003.)

>>> fromimportlibimportimport_module
>>> anydbm=import_module('anydbm')# Standard absolute import
>>> anydbm
<module 'anydbm' from '/p/python/Lib/anydbm.py'>
>>> # Relative import
>>> file_util=import_module('..file_util','distutils.command')
>>> file_util
<module 'distutils.file_util' from '/python/Lib/distutils/file_util.pyc'>

python-munittestdiscover-stest

withself.assertRaises(KeyError):
{}['foo']

构建和 C API 的改变¶

Changes to Python's build process and to the C API include:

• The latest release of the GNU Debugger, GDB 7, can be scripted

  using Python.

  When you begin debugging an executable program P, GDB will look for

  a file named P-gdb.py and automatically read it. Dave Malcolm

  contributed a python-gdb.py that adds a number of

  commands useful when debugging Python itself. For example,

  py-up and py-down go up or down one Python stack frame,

  which usually corresponds to several C stack frames. py-print

  prints the value of a Python variable, and py-bt prints the

  Python stack trace. (Added as a result of bpo-8032.)

• If you use the .gdbinit file provided with Python,

  the "pyo" macro in the 2.7 version now works correctly when the thread being

  debugged doesn't hold the GIL; the macro now acquires it before printing.

  (Contributed by Victor Stinner; bpo-3632.)

• Py_AddPendingCall() is now thread-safe, letting any

  worker thread submit notifications to the main Python thread. This

  is particularly useful for asynchronous IO operations.

  (Contributed by Kristján Valur Jónsson; bpo-4293.)

• New function: PyCode_NewEmpty() creates an empty code object;

  only the filename, function name, and first line number are required.

  This is useful for extension modules that are attempting to

  construct a more useful traceback stack. Previously such

  extensions needed to call PyCode_New(), which had many

  more arguments. (Added by Jeffrey Yasskin.)

• New function: PyErr_NewExceptionWithDoc() creates a new

  exception class, just as the existing PyErr_NewException() does,

  but takes an extra char* argument containing the docstring for the

  new exception class. (Added by 'lekma' on the Python bug tracker;

  bpo-7033.)

• New function: PyFrame_GetLineNumber() takes a frame object

  and returns the line number that the frame is currently executing.

  Previously code would need to get the index of the bytecode

  instruction currently executing, and then look up the line number

  corresponding to that address. (Added by Jeffrey Yasskin.)

• New functions: PyLong_AsLongAndOverflow() and

  PyLong_AsLongLongAndOverflow() approximates a Python long

  integer as a C long or longlong.

  If the number is too large to fit into

  the output type, an overflow flag is set and returned to the caller.

  (Contributed by Case Van Horsen; bpo-7528 and bpo-7767.)

• New function: stemming from the rewrite of string-to-float conversion,

  a new PyOS_string_to_double() function was added. The old

  PyOS_ascii_strtod() and PyOS_ascii_atof() functions

  are now deprecated.

• New function: PySys_SetArgvEx() sets the value of

  sys.argv and can optionally update sys.path to include the

  directory containing the script named by sys.argv[0] depending

  on the value of an updatepath parameter.

  This function was added to close a security hole for applications

  that embed Python. The old function, PySys_SetArgv(), would

  always update sys.path, and sometimes it would add the current

  directory. This meant that, if you ran an application embedding

  Python in a directory controlled by someone else, attackers could

  put a Trojan-horse module in the directory (say, a file named

  os.py) that your application would then import and run.

  If you maintain a C/C++ application that embeds Python, check

  whether you're calling PySys_SetArgv() and carefully consider

  whether the application should be using PySys_SetArgvEx()

  with updatepath set to false.

  Security issue reported as CVE-2008-5983;

  discussed in bpo-5753, and fixed by Antoine Pitrou.

• New macros: the Python header files now define the following macros:

  Py_ISALNUM,

  Py_ISALPHA,

  Py_ISDIGIT,

  Py_ISLOWER,

  Py_ISSPACE,

  Py_ISUPPER,

  Py_ISXDIGIT,

  Py_TOLOWER, and Py_TOUPPER.

  All of these functions are analogous to the C

  standard macros for classifying characters, but ignore the current

  locale setting, because in

  several places Python needs to analyze characters in a

  locale-independent way. (Added by Eric Smith;

  bpo-5793.)

• Removed function: PyEval_CallObject is now only available

  as a macro. A function version was being kept around to preserve

  ABI linking compatibility, but that was in 1997; it can certainly be

  deleted by now. (Removed by Antoine Pitrou; bpo-8276.)

• New format codes: the PyFormat_FromString(),

  PyFormat_FromStringV(), and PyErr_Format() functions now

  accept %lld and %llu format codes for displaying

  C's longlong types.

  (Contributed by Mark Dickinson; bpo-7228.)

• The complicated interaction between threads and process forking has

  been changed. Previously, the child process created by

  os.fork() might fail because the child is created with only a

  single thread running, the thread performing the os.fork().

  If other threads were holding a lock, such as Python's import lock,

  when the fork was performed, the lock would still be marked as

  "held" in the new process. But in the child process nothing would

  ever release the lock, since the other threads weren't replicated,

  and the child process would no longer be able to perform imports.

  Python 2.7 acquires the import lock before performing an

  os.fork(), and will also clean up any locks created using the

  threading module. C extension modules that have internal

  locks, or that call fork() themselves, will not benefit

  from this clean-up.

  (Fixed by Thomas Wouters; bpo-1590864.)

• The Py_Finalize() function now calls the internal

  threading._shutdown() function; this prevents some exceptions from

  being raised when an interpreter shuts down.

  (Patch by Adam Olsen; bpo-1722344.)

• When using the PyMemberDef structure to define attributes

  of a type, Python will no longer let you try to delete or set a

  T_STRING_INPLACE attribute.

• Global symbols defined by the ctypes module are now prefixed

  with Py, or with _ctypes. (Implemented by Thomas

  Heller; bpo-3102.)

• New configure option: the --with-system-expat switch allows

  building the pyexpat module to use the system Expat library.

  (Contributed by Arfrever Frehtes Taifersar Arahesis; bpo-7609.)

• New configure option: the

  --with-valgrind option will now disable the pymalloc

  allocator, which is difficult for the Valgrind memory-error detector

  to analyze correctly.

  Valgrind will therefore be better at detecting memory leaks and

  overruns. (Contributed by James Henstridge; bpo-2422.)

• New configure option: you can now supply an empty string to

  --with-dbmliborder= in order to disable all of the various

  DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis;

  bpo-6491.)

• The configure script now checks for floating-point rounding bugs

  on certain 32-bit Intel chips and defines a X87_DOUBLE_ROUNDING

  preprocessor definition. No code currently uses this definition,

  but it's available if anyone wishes to use it.

  (Added by Mark Dickinson; bpo-2937.)

  configure also now sets a LDCXXSHARED Makefile

  variable for supporting C++ linking. (Contributed by Arfrever

  Frehtes Taifersar Arahesis; bpo-1222585.)

• The build process now creates the necessary files for pkg-config

  support. (Contributed by Clinton Roy; bpo-3585.)

• The build process now supports Subversion 1.7. (Contributed by

  Arfrever Frehtes Taifersar Arahesis; bpo-6094.)

void*vtable;
if(!PyCapsule_IsValid(capsule,"mymodule.CAPI"){
PyErr_SetString(PyExc_ValueError,"argument type invalid");
returnNULL;
}
vtable=PyCapsule_GetPointer(capsule,"mymodule.CAPI");

Other Changes and Fixes¶

• Two benchmark scripts, iobench and ccbench, were

  added to the Tools directory. iobench measures the

  speed of the built-in file I/O objects returned by open()

  while performing various operations, and ccbench is a

  concurrency benchmark that tries to measure computing throughput,

  thread switching latency, and IO processing bandwidth when

  performing several tasks using a varying number of threads.

• The Tools/i18n/msgfmt.py script now understands plural

  forms in .po files. (Fixed by Martin von Löwis;

  bpo-5464.)

• When importing a module from a .pyc or .pyo file

  with an existing .py counterpart, the co_filename

  attributes of the resulting code objects are overwritten when the

  original filename is obsolete. This can happen if the file has been

  renamed, moved, or is accessed through different paths. (Patch by

  Ziga Seilnacht and Jean-Paul Calderone; bpo-1180193.)

• The regrtest.py script now takes a --randseed=

  switch that takes an integer that will be used as the random seed

  for the -r option that executes tests in random order.

  The -r option also reports the seed that was used

  (Added by Collin Winter.)

• Another regrtest.py switch is -j, which

  takes an integer specifying how many tests run in parallel. This

  allows reducing the total runtime on multi-core machines.

  This option is compatible with several other options, including the

  -R switch which is known to produce long runtimes.

  (Added by Antoine Pitrou, bpo-6152.) This can also be used

  with a new -F switch that runs selected tests in a loop

  until they fail. (Added by Antoine Pitrou; bpo-7312.)

• When executed as a script, the py_compile.py module now

  accepts '-' as an argument, which will read standard input for

  the list of filenames to be compiled. (Contributed by Piotr

  Ożarowski; bpo-8233.)

移植到 Python 2.7¶

This section lists previously described changes and other bugfixes

that may require changes to your code:

• The range() function processes its arguments more

  consistently; it will now call __int__() on non-float,

  non-integer arguments that are supplied to it. (Fixed by Alexander

  Belopolsky; bpo-1533.)

• The string format() method changed the default precision used

  for floating-point and complex numbers from 6 decimal

  places to 12, which matches the precision used by str().

  (Changed by Eric Smith; bpo-5920.)

• Because of an optimization for the with statement, the special

  methods __enter__() and __exit__() must belong to the object's

  type, and cannot be directly attached to the object's instance. This

  affects new-style classes (derived from object) and C extension

  types. (bpo-6101.)

• Due to a bug in Python 2.6, the exc_value parameter to

  __exit__() methods was often the string representation of the

  exception, not an instance. This was fixed in 2.7, so exc_value

  will be an instance as expected. (Fixed by Florent Xicluna;

  bpo-7853.)

• When a restricted set of attributes were set using __slots__,

  deleting an unset attribute would not raise AttributeError

  as you would expect. Fixed by Benjamin Peterson; bpo-7604.)

In the standard library:

• Operations with datetime instances that resulted in a year

  falling outside the supported range didn't always raise

  OverflowError. Such errors are now checked more carefully

  and will now raise the exception. (Reported by Mark Leander, patch

  by Anand B. Pillai and Alexander Belopolsky; bpo-7150.)

• When using Decimal instances with a string's

  format() method, the default alignment was previously

  left-alignment. This has been changed to right-alignment, which might

  change the output of your programs.

  (Changed by Mark Dickinson; bpo-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;

  bpo-7279.)

• The ElementTree library, xml.etree, no longer escapes

  ampersands and angle brackets when outputting an XML processing

  instruction (which looks like <?xml-stylesheet href="#style1"?>)

  or comment (which looks like <!-- comment -->).

  (Patch by Neil Muller; bpo-2746.)

• The readline() method of StringIO objects now does

  nothing when a negative length is requested, as other file-like

  objects do. (bpo-7348).

• 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; bpo-8451.)

• 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; bpo-7357.)

• The urlparse module's urlsplit() now handles

  unknown URL schemes in a fashion compliant with RFC 3986: if the

  URL is of the form "<something>://...", the text before the

  :// is treated as the scheme, even if it's a made-up scheme that

  the module doesn't know about. This change may break code that

  worked around the old behaviour. For example, Python 2.6.4 or 2.5

  will return the following:

  >>> importurlparse
  >>> urlparse.urlsplit('invented://host/filename?query')
  ('invented', '', '//host/filename?query', '', '')
  

  Python 2.7 (and Python 2.6.5) will return:

  >>> importurlparse
  >>> urlparse.urlsplit('invented://host/filename?query')
  ('invented', 'host', '/filename?query', '', '')
  

  (Python 2.7 actually produces slightly different output, since it

  returns a named tuple instead of a standard tuple.)

对于C扩展：

• C extensions that use integer format codes with the PyArg_Parse*

  family of functions will now raise a TypeError exception

  instead of triggering a DeprecationWarning (bpo-5080).

• Use the new PyOS_string_to_double() function instead of the old

  PyOS_ascii_strtod() and PyOS_ascii_atof() functions,

  which are now deprecated.

对于嵌入Python的应用程序：

• The PySys_SetArgvEx() function was added, letting

  applications close a security hole when the existing

  PySys_SetArgv() function was used. Check whether you're

  calling PySys_SetArgv() and carefully consider whether the

  application should be using PySys_SetArgvEx() with

  updatepath set to false.

New Features Added to Python 2.7 Maintenance Releases¶

New features may be added to Python 2.7 maintenance releases when the

situation genuinely calls for it. Any such additions must go through

the Python Enhancement Proposal process, and make a compelling case for why

they can't be adequately addressed by either adding the new feature solely to

Python 3, or else by publishing it on the Python Package Index.

In addition to the specific proposals listed below, there is a general

exemption allowing new -3 warnings to be added in any Python 2.7

maintenance release.

importurllib2
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")
urllib2.urlopen("https://invalid-cert",context=context)