# 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'