# 21.12. `http.client` — HTTP 协议客户端

源代码： Lib/http/client.py

这个模块定义了实现 HTTP 和 HTTPS 协议客户端的类。 它通常不直接使用 — 模块 `urllib.request` 用它来处理使用 HTTP 和 HTTPS 的 URL。

参见

Requests 包 推荐用于更高层级的 HTTP 客户端接口。

注解

HTTPS 支持仅在编译 Python 时启用了 SSL 支持的情况下（通过 `ssl` 模块）可用。

该模块支持以下类：

class `http.client.``HTTPConnection`(host, port=None, [timeout, ]source_address=None)

  An `HTTPConnection` instance represents one transaction with an HTTP server. It should be instantiated passing it a host and optional port number. If no port number is passed, the port is extracted from the host string if it has the form `host:port`, else the default HTTP port (80) is used. If the optional timeout parameter is given, blocking operations (like connection attempts) will timeout after that many seconds (if it is not given, the global default timeout setting is used). The optional source_address parameter may be a tuple of a (host, port) to use as the source address the HTTP connection is made from.

  举个例子，以下调用都是创建连接到同一主机和端口的服务器的实例：

      >>> h1 = http.client.HTTPConnection('www.python.org')
      >>> h2 = http.client.HTTPConnection('www.python.org:80')
      >>> h3 = http.client.HTTPConnection('www.python.org', 80)
      >>> h4 = http.client.HTTPConnection('www.python.org', 80, timeout=10)

  在 3.2 版更改: 添加了 source_address。

  在 3.4 版更改: 删除了 strict 参数，不再支持 HTTP 0.9 风格的“简单响应”。

class `http.client.``HTTPSConnection`(host, port=None, key_file=None, cert_file=None, [timeout, ]source_address=None, *, context=None, check_hostname=None)

  `HTTPConnection` 的子类，使用 SSL 与安全服务器进行通信。 默认端口为 `443`。 如果指定了 context，它必须为一个描述 SSL 各选项的 `ssl.SSLContext` 实例。

  请参阅 Security considerations 了解有关最佳实践的更多信息。

  在 3.2 版更改: 添加了 source_address, context 和 check_hostname。

  在 3.2 版更改: 这个类目前会在可能的情况下（即如果 `ssl.HAS_SNI` 为真值）支持 HTTPS 虚拟主机。

  在 3.4 版更改: 删除了 strict 参数，不再支持 HTTP 0.9 风格的“简单响应”。

  在 3.4.3 版更改: 目前这个类在默认情况下会执行所有必要的证书和主机检查。 要回复到先前的非验证行为，可以将 `ssl._create_unverified_context()` 传递给 context 参数。

  3.6 版后已移除: key_file 和 cert_file 已弃用并转而推荐 context。 请改用 `ssl.SSLContext.load_cert_chain()` 或让 `ssl.create_default_context()` 为你选择系统所信任的 CA 证书。

  check_hostname 参数也已弃用；应当改用 context 的 `ssl.SSLContext.check_hostname` 属性。

class `http.client.``HTTPResponse`(sock, debuglevel=0, method=None, url=None)

  在成功连接后返回类的实例，而不是由用户直接实例化。

  在 3.4 版更改: 删除了 strict 参数，不再支持HTTP 0.9 风格的“简单响应”。

下列异常可以适当地被引发:

exception `http.client.``HTTPException`

  此模块中其他异常的基类。 它是 `Exception` 的一个子类。

exception `http.client.``NotConnected`

  `HTTPException` 的一个子类。

exception `http.client.``InvalidURL`

  `HTTPException` 的一个子类，如果给出了一个非数字或为空值的端口就会被引发。

exception `http.client.``UnknownProtocol`

  `HTTPException` 的一个子类。

exception `http.client.``UnknownTransferEncoding`

  `HTTPException` 的一个子类。

exception `http.client.``UnimplementedFileMode`

  `HTTPException` 的一个子类。

exception `http.client.``IncompleteRead`

  `HTTPException` 的一个子类。

exception `http.client.``ImproperConnectionState`

  `HTTPException` 的一个子类。

exception `http.client.``CannotSendRequest`

  `ImproperConnectionState` 的一个子类。

exception `http.client.``CannotSendHeader`

  `ImproperConnectionState` 的一个子类。

exception `http.client.``ResponseNotReady`

  `ImproperConnectionState` 的一个子类。

exception `http.client.``BadStatusLine`

  `HTTPException` 的一个子类。 如果服务器反馈了一个我们不理解的 HTTP 状态码就会被引发。

exception `http.client.``LineTooLong`

  `HTTPException` 的一个子类。 如果在 HTTP 协议中从服务器接收到过长的行就会被引发。

exception `http.client.``RemoteDisconnected`

  `ConnectionResetError` 和 `BadStatusLine` 的一个子类。 当尝试读取响应时的结果是未从连接读取到数据时由 `HTTPConnection.getresponse()` 引发，表明远端已关闭连接。

  3.5 新版功能: 在此之前引发的异常为 `BadStatusLine``('')`。

此模块中定义的常量为：

`http.client.``HTTP_PORT`

  HTTP 协议默认的端口号 (总是 `80`)。

`http.client.``HTTPS_PORT`

  HTTPS 协议默认的端口号 (总是 `443`)。

`http.client.``responses`

  这个字典把 HTTP 1.1 状态码映射到 W3C 名称。

  例如：`http.client.responses[http.client.NOT_FOUND]` 是 `'NOT FOUND` （未发现）。

本模块中可用的 HTTP 状态码常量可以参见 HTTP 状态码 。

## 21.12.1. HTTPConnection 对象

`HTTPConnection` 实例拥有以下方法：

`HTTPConnection.``request`(method, url, body=None, headers={}, *, encode_chunked=False)

  这会使用 HTTP 请求方法 method 和选择器 url 向服务器发送请求。

  如果给定 body，那么给定的数据会在信息头完成之后发送。它可能是一个 `str` 、一个 bytes-like object 、一个打开的 file object，或者 `bytes` 迭代器。如果 body 是字符串，它会按 HTTP 默认的 ISO-8859-1 编码；如果是一个字节类对象，它会按原样发送；如果是 file object ，文件的内容会被发送，这个文件对象应该支持 `read()` 方法。如果这个文件对象是一个 `io.TextIOBase` 实例， `read()` 方法返回的数据会按 ISO-8859-1 编码，否则 `read()` 方法返回的数据会按原样发送；如果 body 是一个迭代器，迭代器中的元素会被发送，直到迭代器耗尽。

  headers 参数应是额外的随请求发送的 HTTP 信息头的字典。

  如果 headers 既不包含 Content-Length 也没有 Transfer-Encoding，但存在请求正文，那么这些头字段中的一个会自动设定。如果 body 是 `None`，那么对于要求正文的方法 (`PUT`，`POST`，和 `PATCH`)，Content-Length 头会被设为 `0`。如果 body 是字符串或者类似字节的对象，并且也不是 文件，Content-Length 头会设为正文的长度。任何其他类型的 body （一般是文件或迭代器）会按块编码，这时会自动设定 Transfer-Encoding 头以代替 Content-Length。

  在 headers 中指定 Transfer-Encoding 时， encode_chunked 是唯一相关的参数。如果 encode_chunked 为 `False`，HTTPConnection 对象会假定所有的编码都由调用代码处理。如果为 `True`，正文会按块编码。

  注解

  HTTP 协议在 1.1 版中添加了块传输编码。除非明确知道 HTTP 服务器可以处理 HTTP 1.1，调用者要么必须指定 Content-Length，要么必须传入 `str` 或字节类对象，注意该对象不能是表达 body 的文件。

  3.2 新版功能: body 现在可以是可迭代对象了。

  在 3.6 版更改: 如果 Content-Length 和 Transfer-Encoding 都没有在 headers 中设置，文件和可迭代的 body 对象现在会按块编码。添加了 encode_chunked 参数。不会尝试去确定文件对象的 Content-Length。

`HTTPConnection.``getresponse`()

  Should be called after a request is sent to get the response from the server. Returns an `HTTPResponse` instance.

  注解

  Note that you must have read the whole response before you can send a new request to the server.

  在 3.5 版更改: If a `ConnectionError` or subclass is raised, the `HTTPConnection` object will be ready to reconnect when a new request is sent.

`HTTPConnection.``set_debuglevel`(level)

  Set the debugging level. The default debug level is `0`, meaning no debugging output is printed. Any value greater than `0` will cause all currently defined debug output to be printed to stdout. The `debuglevel` is passed to any new `HTTPResponse` objects that are created.

  3.1 新版功能.

`HTTPConnection.``set_tunnel`(host, port=None, headers=None)

  Set the host and the port for HTTP Connect Tunnelling. This allows running the connection through a proxy server.

  The host and port arguments specify the endpoint of the tunneled connection (i.e. the address included in the CONNECT request, not the address of the proxy server).

  The headers argument should be a mapping of extra HTTP headers to send with the CONNECT request.

  For example, to tunnel through a HTTPS proxy server running locally on port 8080, we would pass the address of the proxy to the `HTTPSConnection` constructor, and the address of the host that we eventually want to reach to the `set_tunnel()` method:

      >>> import http.client
      >>> conn = http.client.HTTPSConnection("localhost", 8080)
      >>> conn.set_tunnel("www.python.org")
      >>> conn.request("HEAD","/index.html")

  3.2 新版功能.

`HTTPConnection.``connect`()

  Connect to the server specified when the object was created. By default, this is called automatically when making a request if the client does not already have a connection.

`HTTPConnection.``close`()

  关闭到服务器的连接。

As an alternative to using the `request()` method described above, you can also send your request step by step, by using the four functions below.

`HTTPConnection.``putrequest`(method, url, skip_host=False, skip_accept_encoding=False)

  This should be the first call after the connection to the server has been made. It sends a line to the server consisting of the method string, the url string, and the HTTP version (`HTTP/1.1`). To disable automatic sending of `Host:` or `Accept-Encoding:` headers (for example to accept additional content encodings), specify skip_host or skip_accept_encoding with non-False values.

`HTTPConnection.``putheader`(header, argument[, ...])

  Send an RFC 822-style header to the server. It sends a line to the server consisting of the header, a colon and a space, and the first argument. If more arguments are given, continuation lines are sent, each consisting of a tab and an argument.

`HTTPConnection.``endheaders`(message_body=None, *, encode_chunked=False)

  Send a blank line to the server, signalling the end of the headers. The optional message_body argument can be used to pass a message body associated with the request.

  If encode_chunked is `True`, the result of each iteration of message_body will be chunk-encoded as specified in RFC 7230, Section 3.3.1. How the data is encoded is dependent on the type of message_body. If message_body implements the buffer interface the encoding will result in a single chunk. If message_body is a `collections.Iterable`, each iteration of message_body will result in a chunk. If message_body is a file object, each call to `.read()` will result in a chunk. The method automatically signals the end of the chunk-encoded data immediately after message_body.

  注解

  Due to the chunked encoding specification, empty chunks yielded by an iterator body will be ignored by the chunk-encoder. This is to avoid premature termination of the read of the request by the target server due to malformed encoding.

  3.6 新版功能: Chunked encoding support. The encode_chunked parameter was added.

`HTTPConnection.``send`(data)

  Send data to the server. This should be used directly only after the `endheaders()` method has been called and before `getresponse()` is called.

## 21.12.2. HTTPResponse 对象

An `HTTPResponse` instance wraps the HTTP response from the server. It provides access to the request headers and the entity body. The response is an iterable object and can be used in a with statement.

在 3.5 版更改: The `io.BufferedIOBase` interface is now implemented and all of its reader operations are supported.

`HTTPResponse.``read`([amt])

  Reads and returns the response body, or up to the next amt bytes.

`HTTPResponse.``readinto`(b)

  Reads up to the next len(b) bytes of the response body into the buffer b. Returns the number of bytes read.

  3.3 新版功能.

`HTTPResponse.``getheader`(name, default=None)

  Return the value of the header name, or default if there is no header matching name. If there is more than one header with the name name, return all of the values joined by ‘, ‘. If ‘default’ is any iterable other than a single string, its elements are similarly returned joined by commas.

`HTTPResponse.``getheaders`()

  Return a list of (header, value) tuples.

`HTTPResponse.``fileno`()

  Return the `fileno` of the underlying socket.

`HTTPResponse.``msg`

  A `http.client.HTTPMessage` instance containing the response headers. `http.client.HTTPMessage` is a subclass of `email.message.Message`.

`HTTPResponse.``version`

  HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1.

`HTTPResponse.``status`

  由服务器返回的状态码。

`HTTPResponse.``reason`

  Reason phrase returned by server.

`HTTPResponse.``debuglevel`

  A debugging hook. If `debuglevel` is greater than zero, messages will be printed to stdout as the response is read and parsed.

`HTTPResponse.``closed`

  Is `True` if the stream is closed.

## 21.12.3. 示例

Here is an example session that uses the `GET` method:

    >>> import http.client
    >>> conn = http.client.HTTPSConnection("www.python.org")
    >>> conn.request("GET", "/")
    >>> r1 = conn.getresponse()
    >>> print(r1.status, r1.reason)
    200 OK
    >>> data1 = r1.read()  # This will return entire content.
    >>> # The following example demonstrates reading data in chunks.
    >>> conn.request("GET", "/")
    >>> r1 = conn.getresponse()
    >>> while not r1.closed:
    ...     print(r1.read(200))  # 200 bytes
    b'<!doctype html>\n<!--[if"...
    ...
    >>> # Example of an invalid request
    >>> conn.request("GET", "/parrot.spam")
    >>> r2 = conn.getresponse()
    >>> print(r2.status, r2.reason)
    404 Not Found
    >>> data2 = r2.read()
    >>> conn.close()

Here is an example session that uses the `HEAD` method. Note that the `HEAD` method never returns any data.

    >>> import http.client
    >>> conn = http.client.HTTPSConnection("www.python.org")
    >>> conn.request("HEAD", "/")
    >>> res = conn.getresponse()
    >>> print(res.status, res.reason)
    200 OK
    >>> data = res.read()
    >>> print(len(data))
    0
    >>> data == b''
    True

Here is an example session that shows how to `POST` requests:

    >>> import http.client, urllib.parse
    >>> params = urllib.parse.urlencode({'@number': 12524, '@type': 'issue', '@action': 'show'})
    >>> headers = {"Content-type": "application/x-www-form-urlencoded",
    ...            "Accept": "text/plain"}
    >>> conn = http.client.HTTPConnection("bugs.python.org")
    >>> conn.request("POST", "", params, headers)
    >>> response = conn.getresponse()
    >>> print(response.status, response.reason)
    302 Found
    >>> data = response.read()
    >>> data
    b'Redirecting to <a href="http://bugs.python.org/issue12524">http://bugs.python.org/issue12524</a>'
    >>> conn.close()

Client side `HTTP PUT` requests are very similar to `POST` requests. The difference lies only the server side where HTTP server will allow resources to be created via `PUT` request. It should be noted that custom HTTP methods +are also handled in `urllib.request.Request` by sending the appropriate +method attribute.Here is an example session that shows how to do `PUT` request using http.client:

    >>> # This creates an HTTP message
    >>> # with the content of BODY as the enclosed representation
    >>> # for the resource http://localhost:8080/file
    ...
    >>> import http.client
    >>> BODY = "***filecontents***"
    >>> conn = http.client.HTTPConnection("localhost", 8080)
    >>> conn.request("PUT", "/file", BODY)
    >>> response = conn.getresponse()
    >>> print(response.status, response.reason)
    200, OK

## 21.12.4. HTTPMessage Objects

An `http.client.HTTPMessage` instance holds the headers from an HTTP response. It is implemented using the `email.message.Message` class.