# `nntplib` --- NNTP 协议客户端

源代码: Lib/nntplib.py

此模块定义了 `NNTP` 类来实现网络新闻传输协议的客户端。 它可被用于实现一个新闻阅读或发布器，或是新闻自动处理程序。 它兼容了 RFC 3977 以及较旧的 RFC 977 和 RFC 2980。

下面是此模块的两个简单用法示例。 列出某个新闻组的一些统计数据并打印最近 10 篇文章的主题:

    >>> s = nntplib.NNTP('news.gmane.io')
    >>> 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!'

要基于一个二进制文件发布文章 (假定文章包含有效的标头，并且你有在特定新闻组上发布内容的权限):

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

此模块本身定义了以下的类:

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

  返回一个新的 `NNTP` 对象，代表一个对运行于主机 host，在端口 port 上监听的 NNTP 服务器的连接。 可以为套接字连接指定可选的 timeout。 如果提供了可选的 user 和 password，或者如果在 `/.netrc` 中存在适合的凭证并且可选的旗标 usenetrc 为真值，则会使用 `AUTHINFO USER` 和 `AUTHINFO PASS` 命令在服务器上标识和认证用户。 如果可选的旗标 readermode 为真值，则会在执行认证之前发送 `mode reader` 命令。 在某些时候如果你是连接本地机器上的 NNTP 服务器并且想要调用读取者专属命令如 `group` 那么还必须使用读取者模式。 如果你收到预料之外的 `NNTPPermanentError`，你可能需要设置 readermode。 `NNTP` 类支持使用 `with` 语句来无条件地消费 `OSError` 异常并在结束时关闭 NNTP 连接，例如:

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

  引发一个 审计事件 `nntplib.connect` 附带参数 `self`, `host`, `port`。

  引发一个 审计事件 `nntplib.putline`，附带参数 `self`, `line`。

  3.2 版更變: usenetrc 现在默认为 `False`。

  3.3 版更變: 支持了 `with` 语句。

  3.9 版更變: 如果 timeout 参数设置为 0，创建非阻塞套接字时，它将引发 `ValueError` 来阻止该操作。

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

  返回一个新的 `NNTP_SSL` 对象，代表一个对运行于主机 host，在端口 port 上监听的 NNTP 服务器的连接。 `NNTP_SSL` 对象具有与 `NNTP` 对象相同的方法。 如果 port 被省略，则会使用端口 563 (NNTPS)。 ssl_context 也是可选的，且为一个 `SSLContext` 对象。 请阅读 安全考量 来了解最佳实践。 所有其他形参的行为都与 `NNTP` 的相同。

  请注意 RFC 4642 不再推荐使用 563 端口的 SSL，建议改用下文描述的 STARTTLS。 但是，某些服务器只支持前者。

  引发一个 审计事件 `nntplib.connect` 附带参数 `self`, `host`, `port`。

  引发一个 审计事件 `nntplib.putline`，附带参数 `self`, `line`。

  3.2 版新加入.

  3.4 版更變: 本类现在支持通过 `ssl.SSLContext.check_hostname` 和 服务器名称提示 （参阅 `ssl.HAS_SNI`）进行主机名检查。

  3.9 版更變: 如果 timeout 参数设置为 0，创建非阻塞套接字时，它将引发 `ValueError` 来阻止该操作。

exception `nntplib.``NNTPError`

  派生自标准异常 `Exception`，这是 `nntplib` 模块中引发的所有异常的基类。 该类的实例具有以下属性:

  `response`

    可用的服务器响应，为一 `str` 对象。

exception `nntplib.``NNTPReplyError`

  从服务器收到意外答复时，将引发本异常。

exception `nntplib.``NNTPTemporaryError`

  Exception raised when a response code in the range 400--499 is received.

exception `nntplib.``NNTPPermanentError`

  Exception raised when a response code in the range 500--599 is received.

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.

exception `nntplib.``NNTPDataError`

  Exception raised when there is some error in the response data.

## NNTP Objects

When connected, `NNTP` and `NNTP_SSL` objects support the following methods and attributes.

### Attributes

`NNTP.``nntp_version`

  An integer representing the version of the NNTP protocol supported by the server. In practice, this should be `2` for servers advertising RFC 3977 compliance and `1` for others.

  3.2 版新加入.

`NNTP.``nntp_implementation`

  A string describing the software name and version of the NNTP server, or `None` if not advertised by the server.

  3.2 版新加入.

### 方法

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.

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.

3.2 版更變: Many of the following methods have been reworked and fixed, which makes them incompatible with their 3.1 counterparts.

`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.

`NNTP.``getwelcome`()

  返回服务器发送的欢迎消息，作为连接开始的回复。（该消息有时包含与用户有关的免责声明或帮助信息。）

`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.io')
      >>> 'POST' in s.getcapabilities()
      True

  3.2 版新加入.

`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.

  3.2 版新加入.

`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 安全考量 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.

  3.2 版新加入.

  3.4 版更變: 此方法现在支持使用 `ssl.SSLContext.check_hostname` 和 服务器名称指示 (参见 `ssl.HAS_SNI`) 进行主机名检查。

`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.

  This command is frequently disabled by NNTP server administrators.

`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.

  3.2 版更變: group_pattern was added.

`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)

  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. 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>'

  3.2 版新加入.

`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`()

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

`NNTP.``last`()

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

`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`()

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

`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).

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.

## 工具函数

The module also defines the following utility function:

`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'