:mod:`nntplib` --- NNTP protocol client
=======================================

.. module:: nntplib
   :synopsis: NNTP protocol client (requires sockets).


.. index::
   pair: NNTP; protocol
   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`.

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.cwi.nl')
   >>> resp, count, first, last, name = s.group('comp.lang.python')
   >>> print('Group', name, 'has', count, 'articles, range', first, 'to', last)
   Group comp.lang.python has 59 articles, range 3742 to 3803
   >>> resp, subs = s.xhdr('subject', first + '-' + last)
   >>> for id, sub in subs[-10:]: print(id, sub)
   ...
   3792 Re: Removing elements from a list while iterating...
   3793 Re: Who likes Info files?
   3794 Emacs and doc strings
   3795 a few questions about the Mac implementation
   3796 Re: executable python scripts
   3797 Re: executable python scripts
   3798 Re: a few questions about the Mac implementation
   3799 Re: PROPOSAL: A Generic Python Object Interface for Python C Modules
   3802 Re: executable python scripts
   3803 Re: \POSIX{} wait and SIGCHLD
   >>> s.quit()
   '205 news.cwi.nl closing connection.  Goodbye.'

To post an article from a file (this assumes that the article has valid
headers)::

   >>> s = NNTP('news.cwi.nl')
   >>> f = open('/tmp/article')
   >>> s.post(f)
   '240 Article posted successfully.'
   >>> s.quit()
   '205 news.cwi.nl closing connection.  Goodbye.'

The module itself defines the following items:


.. class:: NNTP(host[, port [, user[, password [, readermode][, usenetrc]]]])

   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
   :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.


.. 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:: 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:: 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:: 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.


.. 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.


.. _nntp-objects:

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.


.. method:: NNTP.getwelcome()

   Return the welcome message sent by the server in reply to the initial
   connection.  (This message sometimes contains disclaimers or help information
   that may be relevant to the user.)


.. method:: NNTP.set_debuglevel(level)

   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).


.. method:: NNTP.newgroups(date, time, [file])

   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 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.


.. method:: NNTP.newnews(group, date, time, [file])

   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 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.


.. method:: NNTP.list([file])

   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
   *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 object with that name, write to it  then close it.  If *file* is a 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.


.. 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)``.


.. method:: NNTP.description(group)

   Get a description for a single group *group*.  If more than one group matches
   (if 'group' is a real wildmat string), return the first match.   If no group
   matches, return an empty string.

   This elides the response code from the server.  If the response code is needed,
   use :meth:`descriptions`.


.. 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.


.. method:: NNTP.help([file])

   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 object with that name, write to it  then close it.  If
   *file* is a 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.


.. method:: NNTP.stat(id)

   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 ``'>'``).


.. method:: NNTP.next()

   Send a ``NEXT`` command.  Return as for :meth:`stat`.


.. method:: NNTP.last()

   Send a ``LAST`` command.  Return as for :meth:`stat`.


.. method:: NNTP.head(id)

   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).


.. method:: NNTP.body(id,[file])

   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 object with that name,
   write to it then close it. If *file* is a 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.


.. method:: NNTP.article(id)

   Send an ``ARTICLE`` command, where *id* has the same meaning as for
   :meth:`stat`.  Return as for :meth:`head`.


.. method:: NNTP.slave()

   Send a ``SLAVE`` command.  Return the server's *response*.


.. method:: NNTP.xhdr(header, string, [file])

   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.
   ``'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,
   text)``, where *id* is an article number (as a string) and *text* is the text of
   the requested header for that article. If the *file* parameter is supplied, then
   the output of the  ``XHDR`` 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 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.


.. method:: NNTP.post(file)

   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 object with that name,
   write to it  then close it.  If *file* is a 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 object with that name, write to it  then close it.  If *file*
   is a 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.


.. 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.


.. 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.