Issue #9360: Cleanup and improvements to the nntplib module. The API
now conforms to the philosophy of bytes and unicode separation in Python 3.
A test suite has also been added.
diff --git a/Doc/library/nntplib.rst b/Doc/library/nntplib.rst
index c3cbd2b..69adffb 100644
--- a/Doc/library/nntplib.rst
+++ b/Doc/library/nntplib.rst
@@ -11,100 +11,99 @@
single: Network News Transfer Protocol
This module defines the class :class:`NNTP` which implements the client side of
-the NNTP protocol. It can be used to implement a news reader or poster, or
-automated news processors. For more information on NNTP (Network News Transfer
-Protocol), see Internet :rfc:`977`.
+the Network News Transfer Protocol. It can be used to implement a news reader
+or poster, or automated news processors. It is compatible with :rfc:`3977`
+as well as the older :rfc:`977` and :rfc:`2980`.
Here are two small examples of how it can be used. To list some statistics
about a newsgroup and print the subjects of the last 10 articles::
- >>> s = NNTP('news.gmane.org')
+ >>> s = nntplib.NNTP('news.gmane.org')
>>> resp, count, first, last, name = s.group('gmane.comp.python.committers')
>>> print('Group', name, 'has', count, 'articles, range', first, 'to', last)
- Group gmane.comp.python.committers has 1071 articles, range 1 to 1071
- >>> resp, subs = s.xhdr('subject', first + '-' + last)
- >>> for id, sub in subs[-10:]: print(id, sub)
+ Group gmane.comp.python.committers has 1096 articles, range 1 to 1096
+ >>> resp, overviews = s.over((last - 9, last))
+ >>> for id, over in overviews:
+ ... print(id, nntplib.decode_header(over['subject']))
...
- 1062 Re: Mercurial Status?
- 1063 Re: [python-committers] (Windows) buildbots on 3.x
- 1064 Re: Mercurial Status?
- 1065 Re: Mercurial Status?
- 1066 Python 2.6.6 status
- 1067 Commit Privileges for Ask Solem
- 1068 Re: Commit Privileges for Ask Solem
- 1069 Re: Commit Privileges for Ask Solem
- 1070 Re: Commit Privileges for Ask Solem
- 1071 2.6.6 rc 2
+ 1087 Re: Commit privileges for Łukasz Langa
+ 1088 Re: 3.2 alpha 2 freeze
+ 1089 Re: 3.2 alpha 2 freeze
+ 1090 Re: Commit privileges for Łukasz Langa
+ 1091 Re: Commit privileges for Łukasz Langa
+ 1092 Updated ssh key
+ 1093 Re: Updated ssh key
+ 1094 Re: Updated ssh key
+ 1095 Hello fellow committers!
+ 1096 Re: Hello fellow committers!
>>> s.quit()
'205 Bye!'
-To post an article from a file (this assumes that the article has valid
+To post an article from a binary file (this assumes that the article has valid
headers, and that you have right to post on the particular newsgroup)::
- >>> s = NNTP('news.gmane.org')
- >>> f = open('/tmp/article')
+ >>> s = nntplib.NNTP('news.gmane.org')
+ >>> f = open('/tmp/article.txt', 'rb')
>>> s.post(f)
'240 Article posted successfully.'
>>> s.quit()
'205 Bye!'
-The module itself defines the following items:
+The module itself defines the following classes:
-.. class:: NNTP(host[, port [, user[, password [, readermode][, usenetrc]]]])
+.. class:: NNTP(host, port=119, user=None, password=None, readermode=None, usenetrc=True, [timeout])
Return a new instance of the :class:`NNTP` class, representing a connection
- to the NNTP server running on host *host*, listening at port *port*. The
- default *port* is 119. If the optional *user* and *password* are provided,
- or if suitable credentials are present in :file:`/.netrc` and the optional
- flag *usenetrc* is true (the default), the ``AUTHINFO USER`` and ``AUTHINFO
- PASS`` commands are used to identify and authenticate the user to the server.
- If the optional flag *readermode* is true, then a ``mode reader`` command is
- sent before authentication is performed. Reader mode is sometimes necessary
- if you are connecting to an NNTP server on the local machine and intend to
- call reader-specific commands, such as ``group``. If you get unexpected
+ to the NNTP server running on host *host*, listening at port *port*.
+ An optional *timeout* can be specified for the socket connection.
+ If the optional *user* and *password* are provided, or if suitable
+ credentials are present in :file:`/.netrc` and the optional flag *usenetrc*
+ is true (the default), the ``AUTHINFO USER`` and ``AUTHINFO PASS`` commands
+ are used to identify and authenticate the user to the server. If the optional
+ flag *readermode* is true, then a ``mode reader`` command is sent before
+ authentication is performed. Reader mode is sometimes necessary if you are
+ connecting to an NNTP server on the local machine and intend to call
+ reader-specific commands, such as ``group``. If you get unexpected
:exc:`NNTPPermanentError`\ s, you might need to set *readermode*.
*readermode* defaults to ``None``. *usenetrc* defaults to ``True``.
.. exception:: NNTPError
- Derived from the standard exception :exc:`Exception`, this is the base class for
- all exceptions raised by the :mod:`nntplib` module.
+ Derived from the standard exception :exc:`Exception`, this is the base
+ class for all exceptions raised by the :mod:`nntplib` module. Instances
+ of this class have the following attribute:
+
+ .. attribute:: response
+
+ The response of the server if available, as a :class:`str` object.
.. exception:: NNTPReplyError
- Exception raised when an unexpected reply is received from the server. For
- backwards compatibility, the exception ``error_reply`` is equivalent to this
- class.
+ Exception raised when an unexpected reply is received from the server.
.. exception:: NNTPTemporaryError
- Exception raised when an error code in the range 400--499 is received. For
- backwards compatibility, the exception ``error_temp`` is equivalent to this
- class.
+ Exception raised when a response code in the range 400--499 is received.
.. exception:: NNTPPermanentError
- Exception raised when an error code in the range 500--599 is received. For
- backwards compatibility, the exception ``error_perm`` is equivalent to this
- class.
+ Exception raised when a response code in the range 500--599 is received.
.. exception:: NNTPProtocolError
Exception raised when a reply is received from the server that does not begin
- with a digit in the range 1--5. For backwards compatibility, the exception
- ``error_proto`` is equivalent to this class.
+ with a digit in the range 1--5.
.. exception:: NNTPDataError
- Exception raised when there is some error in the response data. For backwards
- compatibility, the exception ``error_data`` is equivalent to this class.
+ Exception raised when there is some error in the response data.
.. _nntp-objects:
@@ -112,10 +111,29 @@
NNTP Objects
------------
-NNTP instances have the following methods. The *response* that is returned as
-the first item in the return tuple of almost all methods is the server's
-response: a string beginning with a three-digit code. If the server's response
-indicates an error, the method raises one of the above exceptions.
+:class:`NNTP` instances have the following methods. The *response* that is
+returned as the first item in the return tuple of almost all methods is the
+server's response: a string beginning with a three-digit code. If the server's
+response indicates an error, the method raises one of the above exceptions.
+
+.. note::
+ Many of the following methods take an optional keyword-only argument *file*.
+ When the *file* argument is supplied, it must be either a :term:`file object`
+ opened for binary writing, or the name of an on-disk file to be written to.
+ The method will then write any data returned by the server (except for the
+ response line and the terminating dot) to the file; any list of lines,
+ tuples or objects that the method normally returns will be empty.
+
+
+.. versionchanged:: 3.2
+ Many of the following methods have been reworked and fixed, which makes
+ them incompatible with their 3.1 counterparts.
+
+
+.. method:: NNTP.quit()
+
+ Send a ``QUIT`` command and close the connection. Once this method has been
+ called, no other methods of the NNTP object should be called.
.. method:: NNTP.getwelcome()
@@ -125,62 +143,70 @@
that may be relevant to the user.)
-.. method:: NNTP.set_debuglevel(level)
+.. method:: NNTP.getcapabilities()
- Set the instance's debugging level. This controls the amount of debugging
- output printed. The default, ``0``, produces no debugging output. A value of
- ``1`` produces a moderate amount of debugging output, generally a single line
- per request or response. A value of ``2`` or higher produces the maximum amount
- of debugging output, logging each line sent and received on the connection
- (including message text).
+ Return the :rfc:`3977` capabilities advertised by the server, as a
+ :class:`dict` instance mapping capability names to (possibly empty) lists
+ of values. On legacy servers which don't understand the ``CAPABILITIES``
+ command, an empty dictionary is returned instead.
+
+ >>> s = NNTP('news.gmane.org')
+ >>> 'POST' in s.getcapabilities()
+ True
+
+ .. versionadded:: 3.2
-.. method:: NNTP.newgroups(date, time, [file])
+.. method:: NNTP.newgroups(date, *, file=None)
- Send a ``NEWGROUPS`` command. The *date* argument should be a string of the
- form ``'yymmdd'`` indicating the date, and *time* should be a string of the form
- ``'hhmmss'`` indicating the time. Return a pair ``(response, groups)`` where
- *groups* is a list of group names that are new since the given date and time. If
- the *file* parameter is supplied, then the output of the ``NEWGROUPS`` command
- is stored in a file. If *file* is a string, then the method will open a file
- object with that name, write to it then close it. If *file* is a :term:`file
- object`, then it will start calling :meth:`write` on it to store the lines of
- the command output. If *file* is supplied, then the returned *list* is an empty list.
+ Send a ``NEWGROUPS`` command. The *date* argument should be a
+ :class:`datetime.date` or :class:`datetime.datetime` object.
+ Return a pair ``(response, groups)`` where *groups* is a list representing
+ the groups that are new since the given *date*. If *file* is supplied,
+ though, then *groups* will be empty.
+
+ >>> from datetime import date, timedelta
+ >>> resp, groups = s.newgroups(date.today() - timedelta(days=3))
+ >>> len(groups)
+ 85
+ >>> groups[0]
+ GroupInfo(group='gmane.network.tor.devel', last='4', first='1', flag='m')
-.. method:: NNTP.newnews(group, date, time, [file])
+.. method:: NNTP.newnews(group, date, *, file=None)
Send a ``NEWNEWS`` command. Here, *group* is a group name or ``'*'``, and
- *date* and *time* have the same meaning as for :meth:`newgroups`. Return a pair
- ``(response, articles)`` where *articles* is a list of message ids. If the
- *file* parameter is supplied, then the output of the ``NEWNEWS`` command is
- stored in a file. If *file* is a string, then the method will open a file
- object with that name, write to it then close it. If *file* is a :term:`file
- object`, then it will start calling :meth:`write` on it to store the lines of the
- command output. If *file* is supplied, then the returned *list* is an empty list.
+ *date* has the same meaning as for :meth:`newgroups`. Return a pair
+ ``(response, articles)`` where *articles* is a list of message ids.
+
+ This command is frequently disabled by NNTP server administrators.
-.. method:: NNTP.list([file])
+.. method:: NNTP.list(*, file=None)
Send a ``LIST`` command. Return a pair ``(response, list)`` where *list* is a
- list of tuples. Each tuple has the form ``(group, last, first, flag)``, where
+ list of tuples representing all the groups available from this NNTP server.
+ Each tuple has the form ``(group, last, first, flag)``, where
*group* is a group name, *last* and *first* are the last and first article
- numbers (as strings), and *flag* is ``'y'`` if posting is allowed, ``'n'`` if
- not, and ``'m'`` if the newsgroup is moderated. (Note the ordering: *last*,
- *first*.) If the *file* parameter is supplied, then the output of the ``LIST``
- command is stored in a file. If *file* is a string, then the method will open
- a file with that name, write to it then close it. If *file* is a :term:`file
- object`, then it will start calling :meth:`write` on it to store the lines of
- the command output. If *file* is supplied, then the returned *list* is an empty
- list.
+ numbers, and *flag* is ``'y'`` if posting is allowed, ``'n'`` if not,
+ and ``'m'`` if the newsgroup is moderated. (Note the ordering: *last*, *first*.)
+
+ This command will often return very large results. It is best to cache the
+ results offline unless you really need to refresh them.
.. method:: NNTP.descriptions(grouppattern)
Send a ``LIST NEWSGROUPS`` command, where *grouppattern* is a wildmat string as
- specified in RFC2980 (it's essentially the same as DOS or UNIX shell wildcard
- strings). Return a pair ``(response, list)``, where *list* is a list of tuples
- containing ``(name, title)``.
+ specified in :rfc:`3977` (it's essentially the same as DOS or UNIX shell wildcard
+ strings). Return a pair ``(response, descriptions)``, where *descriptions*
+ is a dictionary mapping group names to textual descriptions.
+
+ >>> resp, descs = s.descriptions('gmane.comp.python.*')
+ >>> len(descs)
+ 295
+ >>> descs.popitem()
+ ('gmane.comp.python.bio.general', 'BioPython discussion list (Moderated)')
.. method:: NNTP.description(group)
@@ -195,30 +221,73 @@
.. method:: NNTP.group(name)
- Send a ``GROUP`` command, where *name* is the group name. Return a tuple
- ``(response, count, first, last, name)`` where *count* is the (estimated) number
- of articles in the group, *first* is the first article number in the group,
- *last* is the last article number in the group, and *name* is the group name.
- The numbers are returned as strings.
+ Send a ``GROUP`` command, where *name* is the group name. The group is
+ selected as the current group, if it exists. Return a tuple
+ ``(response, count, first, last, name)`` where *count* is the (estimated)
+ number of articles in the group, *first* is the first article number in
+ the group, *last* is the last article number in the group, and *name*
+ is the group name.
-.. method:: NNTP.help([file])
+.. method:: NNTP.over(message_spec, *, file=None)
+
+ Send a ``OVER`` command, or a ``XOVER`` command on legacy servers.
+ *message_spec* can be either a string representing a message id, or
+ a ``(first, last)`` tuple of numbers indicating a range of articles in
+ the current group, or a ``(first, None)`` tuple indicating a range of
+ articles starting from *first* to the last article in the current group,
+ or :const:`None` to select the current article in the current group.
+
+ Return a pair ``(response, overviews)``. *overviews* is a list of
+ ``(article_number, overview)`` tuples, one for each article selected
+ by *message_spec*. Each *overview* is a dictionary with the same number
+ of items, but this number depends on the server. These items are either
+ message headers (the key is then the lower-cased header name) or metadata
+ items (the key is then the metadata name prepended with ``":"``). The
+ following items are guaranteed to be present by the NNTP specification:
+
+ * the ``subject``, ``from``, ``date``, ``message-id`` and ``references``
+ headers
+ * the ``:bytes`` metadata: the number of bytes in the entire raw article
+ (including headers and body)
+ * the ``:lines`` metadata: the number of lines in the article body
+
+ It is advisable to use the :func:`decode_header` function on header
+ values when they may contain non-ASCII characters::
+
+ >>> _, _, first, last, _ = s.group('gmane.comp.python.devel')
+ >>> resp, overviews = s.over((last, last))
+ >>> art_num, over = overviews[0]
+ >>> art_num
+ 117216
+ >>> list(over.keys())
+ ['xref', 'from', ':lines', ':bytes', 'references', 'date', 'message-id', 'subject']
+ >>> over['from']
+ '=?UTF-8?B?Ik1hcnRpbiB2LiBMw7Z3aXMi?= <martin@v.loewis.de>'
+ >>> nntplib.decode_header(over['from'])
+ '"Martin v. Löwis" <martin@v.loewis.de>'
+
+ .. versionadded:: 3.2
+
+
+.. method:: NNTP.help(*, file=None)
Send a ``HELP`` command. Return a pair ``(response, list)`` where *list* is a
- list of help strings. If the *file* parameter is supplied, then the output of
- the ``HELP`` command is stored in a file. If *file* is a string, then the
- method will open a file with that name, write to it then close it. If *file*
- is a :term:`file object`, then it will start calling :meth:`write` on it to store
- the lines of the command output. If *file* is supplied, then the returned *list*
- is an empty list.
+ list of help strings.
-.. method:: NNTP.stat(id)
+.. method:: NNTP.stat(message_spec=None)
- Send a ``STAT`` command, where *id* is the message id (enclosed in ``'<'`` and
- ``'>'``) or an article number (as a string). Return a triple ``(response,
- number, id)`` where *number* is the article number (as a string) and *id* is the
- message id (enclosed in ``'<'`` and ``'>'``).
+ Send a ``STAT`` command, where *message_spec* is either a message id
+ (enclosed in ``'<'`` and ``'>'``) or an article number in the current group.
+ If *message_spec* is omitted or :const:`None`, the current article in the
+ current group is considered. Return a triple ``(response, number, id)``
+ where *number* is the article number and *id* is the message id.
+
+ >>> _, _, first, last, _ = s.group('gmane.comp.python.devel')
+ >>> resp, number, message_id = s.stat(first)
+ >>> number, message_id
+ (9099, '<20030112190404.GE29873@epoch.metaslash.com>')
.. method:: NNTP.next()
@@ -231,28 +300,69 @@
Send a ``LAST`` command. Return as for :meth:`stat`.
-.. method:: NNTP.head(id)
+.. method:: NNTP.article(message_spec=None, *, file=None)
- Send a ``HEAD`` command, where *id* has the same meaning as for :meth:`stat`.
- Return a tuple ``(response, number, id, list)`` where the first three are the
- same as for :meth:`stat`, and *list* is a list of the article's headers (an
- uninterpreted list of lines, without trailing newlines).
+ Send an ``ARTICLE`` command, where *message_spec* has the same meaning as
+ for :meth:`stat`. Return a tuple ``(response, info)`` where *info*
+ is a :class:`~collections.namedtuple` with three members *number*,
+ *message_id* and *lines* (in that order). *number* is the article number
+ in the group (or 0 if the information is not available), *message_id* the
+ message id as a string, and *lines* a list of lines (without terminating
+ newlines) comprising the raw message including headers and body.
+
+ >>> resp, info = s.article('<20030112190404.GE29873@epoch.metaslash.com>')
+ >>> info.number
+ 0
+ >>> info.message_id
+ '<20030112190404.GE29873@epoch.metaslash.com>'
+ >>> len(info.lines)
+ 65
+ >>> info.lines[0]
+ b'Path: main.gmane.org!not-for-mail'
+ >>> info.lines[1]
+ b'From: Neal Norwitz <neal@metaslash.com>'
+ >>> info.lines[-3:]
+ [b'There is a patch for 2.3 as well as 2.2.', b'', b'Neal']
-.. method:: NNTP.body(id,[file])
+.. method:: NNTP.head(message_spec=None, *, file=None)
- Send a ``BODY`` command, where *id* has the same meaning as for :meth:`stat`.
- If the *file* parameter is supplied, then the body is stored in a file. If
- *file* is a string, then the method will open a file with that name, write
- to it then close it. If *file* is a :term:`file object`, then it will start
- calling :meth:`write` on it to store the lines of the body. Return as for
- :meth:`head`. If *file* is supplied, then the returned *list* is an empty list.
+ Same as :meth:`article()`, but sends a ``HEAD`` command. The *lines*
+ returned (or written to *file*) will only contain the message headers, not
+ the body.
-.. method:: NNTP.article(id)
+.. method:: NNTP.body(message_spec=None, *, file=None)
- Send an ``ARTICLE`` command, where *id* has the same meaning as for
- :meth:`stat`. Return as for :meth:`head`.
+ Same as :meth:`article()`, but sends a ``BODY`` command. The *lines*
+ returned (or written to *file*) will only contain the message body, not the
+ headers.
+
+
+.. method:: NNTP.post(data)
+
+ Post an article using the ``POST`` command. The *data* argument is either
+ a :term:`file object` opened for binary reading, or any iterable of bytes
+ objects (representing raw lines of the article to be posted). It should
+ represent a well-formed news article, including the required headers. The
+ :meth:`post` method automatically escapes lines beginning with ``.`` and
+ appends the termination line.
+
+ If the method succeeds, the server's response is returned. If the server
+ refuses posting, a :class:`NNTPReplyError` is raised.
+
+
+.. method:: NNTP.ihave(message_id, data)
+
+ Send an ``IHAVE`` command. *message_id* is the id of the message to send
+ to the server (enclosed in ``'<'`` and ``'>'``). The *data* parameter
+ and the return value are the same as for :meth:`post()`.
+
+
+.. method:: NNTP.date()
+
+ Return a pair ``(response, date)``. *date* is a :class:`~datetime.datetime`
+ object containing the current date and time of the server.
.. method:: NNTP.slave()
@@ -260,10 +370,23 @@
Send a ``SLAVE`` command. Return the server's *response*.
-.. method:: NNTP.xhdr(header, string, [file])
+.. method:: NNTP.set_debuglevel(level)
- Send an ``XHDR`` command. This command is not defined in the RFC but is a
- common extension. The *header* argument is a header keyword, e.g.
+ Set the instance's debugging level. This controls the amount of debugging
+ output printed. The default, ``0``, produces no debugging output. A value of
+ ``1`` produces a moderate amount of debugging output, generally a single line
+ per request or response. A value of ``2`` or higher produces the maximum amount
+ of debugging output, logging each line sent and received on the connection
+ (including message text).
+
+
+The following are optional NNTP extensions defined in :rfc:`2980`. Some of
+them have been superseded by newer commands in :rfc:`3977`.
+
+
+.. method:: NNTP.xhdr(header, string, *, file=None)
+
+ Send an ``XHDR`` command. The *header* argument is a header keyword, e.g.
``'subject'``. The *string* argument should have the form ``'first-last'``
where *first* and *last* are the first and last article numbers to search.
Return a pair ``(response, list)``, where *list* is a list of pairs ``(id,
@@ -276,66 +399,55 @@
returned *list* is an empty list.
-.. method:: NNTP.post(file)
+.. method:: NNTP.xover(start, end, *, file=None)
- Post an article using the ``POST`` command. The *file* argument is an open file
- object which is read until EOF using its :meth:`readline` method. It should be
- a well-formed news article, including the required headers. The :meth:`post`
- method automatically escapes lines beginning with ``.``.
-
-
-.. method:: NNTP.ihave(id, file)
-
- Send an ``IHAVE`` command. *id* is a message id (enclosed in ``'<'`` and
- ``'>'``). If the response is not an error, treat *file* exactly as for the
- :meth:`post` method.
-
-
-.. method:: NNTP.date()
-
- Return a triple ``(response, date, time)``, containing the current date and time
- in a form suitable for the :meth:`newnews` and :meth:`newgroups` methods. This
- is an optional NNTP extension, and may not be supported by all servers.
-
-
-.. method:: NNTP.xgtitle(name, [file])
-
- Process an ``XGTITLE`` command, returning a pair ``(response, list)``, where
- *list* is a list of tuples containing ``(name, title)``. If the *file* parameter
- is supplied, then the output of the ``XGTITLE`` command is stored in a file.
- If *file* is a string, then the method will open a file with that name, write
- to it then close it. If *file* is a :term:`file object`, then it will start
- calling :meth:`write` on it to store the lines of the command output. If *file*
- is supplied, then the returned *list* is an empty list. This is an optional NNTP
- extension, and may not be supported by all servers.
-
- RFC2980 says "It is suggested that this extension be deprecated". Use
- :meth:`descriptions` or :meth:`description` instead.
-
-
-.. method:: NNTP.xover(start, end, [file])
-
- Return a pair ``(resp, list)``. *list* is a list of tuples, one for each
- article in the range delimited by the *start* and *end* article numbers. Each
- tuple is of the form ``(article number, subject, poster, date, id, references,
- size, lines)``. If the *file* parameter is supplied, then the output of the
- ``XOVER`` command is stored in a file. If *file* is a string, then the method
- will open a file with that name, write to it then close it. If *file* is a
- :term:`file object`, then it will start calling :meth:`write` on it to store the
- lines of the command output. If *file* is supplied, then the returned *list* is
- an empty list. This is an optional NNTP extension, and may not be supported by
- all servers.
+ Send an ``XOVER`` command. *start* and *end* are article numbers
+ delimiting the range of articles to select. The return value is the
+ same of for :meth:`over()`. It is recommended to use :meth:`over()`
+ instead, since it will automatically use the newer ``OVER`` command
+ if available.
.. method:: NNTP.xpath(id)
Return a pair ``(resp, path)``, where *path* is the directory path to the
- article with message ID *id*. This is an optional NNTP extension, and may not
- be supported by all servers.
+ article with message ID *id*. Most of the time, this extension is not
+ enabled by NNTP server administrators.
-.. method:: NNTP.quit()
+.. XXX deprecated:
- Send a ``QUIT`` command and close the connection. Once this method has been
- called, no other methods of the NNTP object should be called.
+ .. method:: NNTP.xgtitle(name, *, file=None)
+ Process an ``XGTITLE`` command, returning a pair ``(response, list)``, where
+ *list* is a list of tuples containing ``(name, title)``. If the *file* parameter
+ is supplied, then the output of the ``XGTITLE`` command is stored in a file.
+ If *file* is a string, then the method will open a file with that name, write
+ to it then close it. If *file* is a :term:`file object`, then it will start
+ calling :meth:`write` on it to store the lines of the command output. If *file*
+ is supplied, then the returned *list* is an empty list. This is an optional NNTP
+ extension, and may not be supported by all servers.
+
+ RFC2980 says "It is suggested that this extension be deprecated". Use
+ :meth:`descriptions` or :meth:`description` instead.
+
+
+Utility functions
+-----------------
+
+The module also defines the following utility function:
+
+
+.. function:: decode_header(header_str)
+
+ Decode a header value, un-escaping any escaped non-ASCII characters.
+ *header_str* must be a :class:`str` object. The unescaped value is
+ returned. Using this function is recommended to display some headers
+ in a human readable form::
+
+ >>> decode_header("Some subject")
+ 'Some subject'
+ >>> decode_header("=?ISO-8859-15?Q?D=E9buter_en_Python?=")
+ 'Débuter en Python'
+ >>> decode_header("Re: =?UTF-8?B?cHJvYmzDqG1lIGRlIG1hdHJpY2U=?=")
+ 'Re: problème de matrice'