21.16. "nntplib" --- NNTP プロトコルクライアント
************************************************

**ソースコード:** Lib/nntplib.py

======================================================================

This module defines the class "NNTP" which implements the client side
of 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**.

以下にこのモジュールの使い方の小さな例を二つ示します。ニュースグループ
に関する統計情報を列挙し、最新 10 件の記事を出力するには以下のようにし
ます:

   >>> 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 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']))
   ...
   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!'

バイナリファイルから記事を投稿するには、以下のようにします。 (この例で
は記事番号は有効な番号を指定していて、あなたがそのニュースグループに投
稿する 権限を持っていると仮定しています)

   >>> s = nntplib.NNTP('news.gmane.org')
   >>> f = open('article.txt', 'rb')
   >>> s.post(f)
   '240 Article posted successfully.'
   >>> s.quit()
   '205 Bye!'

このモジュール自体では以下のクラスを定義しています:

class nntplib.NNTP(host, port=119, user=None, password=None, readermode=None, usenetrc=False[, timeout])

   Return a new "NNTP" object, representing a connection 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 "/.netrc" and the optional flag
   *usenetrc* is true, 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*. The "NNTP" class supports the
   "with" statement to unconditionally consume "OSError" exceptions
   and to close the NNTP connection when done, e.g.:

   >>> from nntplib import NNTP
   >>> with NNTP('news.gmane.org') as n:
   ...     n.group('gmane.comp.python.committers')
   ... 
   ('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers')
   >>>

   バージョン 3.2 で変更: *usenetrc* がデフォルトで "False" になりまし
   た。

   バージョン 3.3 で変更: "with" 構文のサポートが追加されました。

class nntplib.NNTP_SSL(host, port=563, user=None, password=None, ssl_context=None, readermode=None, usenetrc=False[, timeout])

   Return a new "NNTP_SSL" object, representing an encrypted
   connection to the NNTP server running on host *host*, listening at
   port *port*.  "NNTP_SSL" objects have the same methods as "NNTP"
   objects.  If *port* is omitted, port 563 (NNTPS) is used.
   *ssl_context* is also optional, and is a "SSLContext" object.
   Please read セキュリティで考慮すべき点 for best practices. All
   other parameters behave the same as for "NNTP".

   Note that SSL-on-563 is discouraged per **RFC 4642**, in favor of
   STARTTLS as described below.  However, some servers only support
   the former.

   バージョン 3.2 で追加.

   バージョン 3.4 で変更: このクラスは "ssl.SSLContext.check_hostname"
   と *Server Name Indication* でホスト名のチェックをサポートしました
   。("ssl.HAS_SNI" を参照してください)。

exception nntplib.NNTPError

   標準の例外 "Exception" から派生しており、 "nntplib" モジュールが送
   出する全ての例外の基底クラスです。このクラスのインスタンスは以下の
   属性を持っています:

   response

      利用可能な場合サーバの応答です。"str" オブジェクトです。

exception nntplib.NNTPReplyError

   サーバから想定外の応答があったときに送出される例外。

exception nntplib.NNTPTemporaryError

   400--499の範囲の応答コードを受け取ったときに送出される例外。

exception nntplib.NNTPPermanentError

   500--599の範囲の応答コードを受け取ったときに送出される例外。

exception nntplib.NNTPProtocolError

   1--5の数字で始まらない応答コードをサーバから受け取ったときに送出さ
   れる例外。

exception nntplib.NNTPDataError

   応答データに何らかのエラーがあったときに送出される例外。


21.16.1. NNTP オブジェクト
==========================

接続されたとき "NNTP" および "NNTP_SSL" オブジェクトは以下のメソッドと
属性をサポートします:


21.16.1.1. 属性
---------------

NNTP.nntp_version

   サーバがサポートしている NNTP プロトコルのバージョンを表す整数です
   。 実際のところ、この値は **RFC 3977** 準拠を通知しているサーバでは
   "2" で、他の場合は "1" のはずです。

   バージョン 3.2 で追加.

NNTP.nntp_implementation

   NNTP サーバのソフトウェア名とバージョンを記述する文字列です。 サー
   バが通知していない場合は "None" です。

   バージョン 3.2 で追加.


21.16.1.2. メソッド
-------------------

全てのメソッドにおける戻り値のタプルで最初の要素となる *response* は、
サーバの応答です: この文字列は 3 桁の数字からなるコードで始まります。
サーバの応答がエラーを示す場合、上記のいずれかの例外が送出されます。

Many of the following methods take an optional keyword-only argument
*file*. When the *file* argument is supplied, it must be either a
*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.

バージョン 3.2 で変更: 以下のメソッドの多くは改訂・修正されました。こ
のため、3.1 のものとは互換性がありません。

NNTP.quit()

   "QUIT" 命令を送信し、接続を閉じます。このメソッドを呼び出した後は、
   NTTP オブジェクトの他のいかなるメソッドも呼び出してはいけません。

NNTP.getwelcome()

   サーバに最初に接続した際に送信される応答中のウェルカムメッセージを
   返します。(このメッセージには時に、ユーザにとって重要な免責事項や
   ヘルプ情報が入っています。)

NNTP.getcapabilities()

   Return the **RFC 3977** capabilities advertised by the server, as a
   "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

   バージョン 3.2 で追加.

NNTP.login(user=None, password=None, usenetrc=True)

   Send "AUTHINFO" commands with the user name and password.  If
   *user* and *password* are "None" and *usenetrc* is true,
   credentials from "~/.netrc" will be used if possible.

   Unless intentionally delayed, login is normally performed during
   the "NNTP" object initialization and separately calling this
   function is unnecessary.  To force authentication to be delayed,
   you must not set *user* or *password* when creating the object, and
   must set *usenetrc* to False.

   バージョン 3.2 で追加.

NNTP.starttls(context=None)

   Send a "STARTTLS" command.  This will enable encryption on the NNTP
   connection.  The *context* argument is optional and should be a
   "ssl.SSLContext" object.  Please read セキュリティで考慮すべき点
   for best practices.

   Note that this may not be done after authentication information has
   been transmitted, and authentication occurs by default if possible
   during a "NNTP" object initialization.  See "NNTP.login()" for
   information on suppressing this behavior.

   バージョン 3.2 で追加.

   バージョン 3.4 で変更: このメソッドは
   "ssl.SSLContext.check_hostname" と *Server Name Indication* でホス
   ト名のチェックをサポートしました。("ssl.HAS_SNI" を参照してください
   )。

NNTP.newgroups(date, *, file=None)

   Send a "NEWGROUPS" command.  The *date* argument should be a
   "datetime.date" or "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')

NNTP.newnews(group, date, *, file=None)

   Send a "NEWNEWS" command.  Here, *group* is a group name or "'*'",
   and *date* has the same meaning as for "newgroups()".  Return a
   pair "(response, articles)" where *articles* is a list of message
   ids.

   このコマンドは NNTP サーバ管理者に無効にされていることがよくありま
   す。

NNTP.list(group_pattern=None, *, file=None)

   Send a "LIST" or "LIST ACTIVE" command.  Return a pair "(response,
   list)" where *list* is a list of tuples representing all the groups
   available from this NNTP server, optionally matching the pattern
   string *group_pattern*.  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, and *flag* usually takes
   one of these values:

   * "y": Local postings and articles from peers are allowed.

   * "m": The group is moderated and all postings must be approved.

   * "n": No local postings are allowed, only articles from peers.

   * "j": Articles from peers are filed in the junk group instead.

   * "x": No local postings, and articles from peers are ignored.

   * "=foo.bar": Articles are filed in the "foo.bar" group instead.

   If *flag* has another value, then the status of the newsgroup
   should be considered unknown.

   This command can return very large results, especially if
   *group_pattern* is not specified.  It is best to cache the results
   offline unless you really need to refresh them.

   バージョン 3.2 で変更: *group_pattern* が追加されました。

NNTP.descriptions(grouppattern)

   Send a "LIST NEWSGROUPS" command, where *grouppattern* is a wildmat
   string as 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)')

NNTP.description(group)

   単一のグループ *group* から説明文字列を取り出します。 ('group' が実
   際には wildmat 文字列で) 複数のグループがマッチした場合、 最初にマ
   ッチしたものを返します。何もマッチしなければ空文字列を返します。

   このメソッドはサーバからの応答コードを省略します。応答コードが必要
   なら、 "descriptions()" を使ってください。

NNTP.group(name)

   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.

NNTP.over(message_spec, *, file=None)

   Send an "OVER" command, or an "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 "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

   The value of each item is either a string, or "None" if not
   present.

   It is advisable to use the "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>'

   バージョン 3.2 で追加.

NNTP.help(*, file=None)

   Send a "HELP" command.  Return a pair "(response, list)" where
   *list* is a list of help strings.

NNTP.stat(message_spec=None)

   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 "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>')

NNTP.next()

   "NEXT" 命令を送信します。 "stat()" のような応答を返します。

NNTP.last()

   "LAST" 命令を送信します。 "stat()" のような応答を返します。

NNTP.article(message_spec=None, *, file=None)

   Send an "ARTICLE" command, where *message_spec* has the same
   meaning as for "stat()".  Return a tuple "(response, info)" where
   *info* is a "namedtuple" with three attributes *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']

NNTP.head(message_spec=None, *, file=None)

   Same as "article()", but sends a "HEAD" command.  The *lines*
   returned (or written to *file*) will only contain the message
   headers, not the body.

NNTP.body(message_spec=None, *, file=None)

   Same as "article()", but sends a "BODY" command.  The *lines*
   returned (or written to *file*) will only contain the message body,
   not the headers.

NNTP.post(data)

   Post an article using the "POST" command.  The *data* argument is
   either a *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 "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 "NNTPReplyError" is raised.

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 "post()".

NNTP.date()

   Return a pair "(response, date)".  *date* is a "datetime" object
   containing the current date and time of the server.

NNTP.slave()

   "SLAVE" 命令を送信します。サーバの *response* を返します。

NNTP.set_debuglevel(level)

   インスタンスのデバッグレベルを設定します。このメソッドは印字される
   デバッグ出力の量を制御します。標準では "0" に設定されていて、 これ
   はデバッグ出力を全く印字しません。 "1" はそこそこの量、一般に NNTP
   要求や応答あたり 1 行のデバッグ出力を生成します。値が "2" やそれ以
   上の場合、(メッセージテキストを含めて) NNTP 接続上で送受信された全
   ての内容を一行ごとにログ出力する、最大限のデバッグ出力を生成します
   。

The following are optional NNTP extensions defined in **RFC 2980**.
Some of them have been superseded by newer commands in **RFC 3977**.

NNTP.xhdr(hdr, str, *, file=None)

   Send an "XHDR" command.  The *hdr* argument is a header keyword,
   e.g. "'subject'".  The *str* 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 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.xover(start, end, *, file=None)

   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 "over()".  It is recommended to use "over()"
   instead, since it will automatically use the newer "OVER" command
   if available.

NNTP.xpath(id)

   Return a pair "(resp, path)", where *path* is the directory path to
   the article with message ID *id*.  Most of the time, this extension
   is not enabled by NNTP server administrators.

   バージョン 3.3 で非推奨: XPATH 拡張は積極的に使われません。


21.16.2. ユーティリティー関数
=============================

このモジュールは以下のユーティリティ関数も定義しています:

nntplib.decode_header(header_str)

   Decode a header value, un-escaping any escaped non-ASCII
   characters. *header_str* must be a "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'
