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# 20.14. `nntplib` — NNTP protocol client

This module defines the 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 `nntplib.``NNTP`(host[, port[, user[, password[, readermode][, usenetrc]]]])
  Return a new instance of the `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 `/.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 `NNTPPermanentError`s, you might need to set readermode. readermode defaults to `None`. usenetrc defaults to `True`.

exception `nntplib.``NNTPError`
  Derived from the standard exception `Exception`, this is the base class for all exceptions raised by the `nntplib` module.

exception `nntplib.``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 `nntplib.``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 `nntplib.``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 `nntplib.``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 `nntplib.``NNTPDataError`
  Exception raised when there is some error in the response data. For backwards compatibility, the exception `error_data` is equivalent to this class.

## 20.14.1. 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.

`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.)

`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).

`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 `write()` on it to store the lines of the command output. If file is supplied, then the returned list is an empty list.

`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 `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 `write()` on it to store the lines of the command output. If file is supplied, then the returned list is an empty list.

`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 `write()` on it to store the lines of the command output. If file is supplied, then the returned list is an empty list.

`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)`.

`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 `descriptions()`.

`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.

`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 `write()` on it to store the lines of the command output. If file is supplied, then the returned list is an empty list.

`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 `'>'`).

`NNTP.``next`()
  Send a `NEXT` command. Return as for `stat()`.

`NNTP.``last`()
  Send a `LAST` command. Return as for `stat()`.

`NNTP.``head`(id)
  Send a `HEAD` command, where id has the same meaning as for `stat()`. Return a tuple `(response, number, id, list)` where the first three are the same as for `stat()`, and list is a list of the article’s headers (an uninterpreted list of lines, without trailing newlines).

`NNTP.``body`(id[, file])
  Send a `BODY` command, where id has the same meaning as for `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 `write()` on it to store the lines of the body. Return as for `head()`. If file is supplied, then the returned list is an empty list.

`NNTP.``article`(id)
  Send an `ARTICLE` command, where id has the same meaning as for `stat()`. Return as for `head()`.

`NNTP.``slave`()
  Send a `SLAVE` command. Return the server’s response.

`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 `write()` on it to store the lines of the command output. If file is supplied, then the returned list is an empty list.

`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 `readline()` method. It should be a well-formed news article, including the required headers. The `post()` method automatically escapes lines beginning with `.`.

`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 `post()` method.

`NNTP.``date`()
  Return a triple `(response, date, time)`, containing the current date and time in a form suitable for the `newnews()` and `newgroups()` methods. This is an optional NNTP extension, and may not be supported by all servers.

`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 `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 `descriptions()` or `description()` instead.

`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 `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.

`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.

`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.

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