# http.client --- HTTP协议客户端

源码: 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 Python 启动了 SSL 支持进行编译时（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, blocksize=8192)

  `HTTPConnection` 的实例代表与 HTTP 的一个连接事务。 它的实例化应当传入一个主机和可选的端口号。 如果没有传入端口号，如果主机字符串的形式为 `主机:端口` 则会从中提取端口，否则将使用默认的 HTTP 端口（80）。 如果给出了可选的 timeout 参数，则阻塞操作（例如连接尝试）将在指定的秒数之后超时（如果未给出，则使用全局默认超时设置）。 可选的 source_address 参数可以为一个 (主机, 端口) 元组，用作进行 HTTP 连接的源地址。 可选的 blocksize 参数可以字节为单位设置缓冲区的大小，用来发送文件类消息体。

  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”。

  在 3.7 版更改: 添加了 blocksize 参数。

class `http.client.``HTTPSConnection`(host, port=None, key_file=None, cert_file=None, [timeout, ]source_address=None, *, context=None, check_hostname=None, blocksize=8192)

  `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”。

This module provides the following function:

`http.client.``parse_headers`(fp)

  Parse the headers from a file pointer fp representing a HTTP request/response. The file has to be a `BufferedIOBase` reader (i.e. not text) and must provide a valid RFC 2822 style header.

  This function returns an instance of `http.client.HTTPMessage` that holds the header fields, but no payload (the same as `HTTPResponse.msg` and `http.server.BaseHTTPRequestHandler.headers`). After returning, the file pointer fp is ready to read the HTTP body.

  注解

  `parse_headers()` does not parse the start-line of a HTTP message; it only parses the `Name: value` lines. The file has to be ready to read these field lines, so the first line should already be consumed before calling the function.

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`

  A subclass of `ImproperConnectionState`.

exception `http.client.``CannotSendHeader`

  A subclass of `ImproperConnectionState`.

exception `http.client.``ResponseNotReady`

  A subclass of `ImproperConnectionState`.

exception `http.client.``BadStatusLine`

  A subclass of `HTTPException`. Raised if a server responds with a HTTP status code that we don't understand.

exception `http.client.``LineTooLong`

  A subclass of `HTTPException`. Raised if an excessively long line is received in the HTTP protocol from the server.

exception `http.client.``RemoteDisconnected`

  A subclass of `ConnectionResetError` and `BadStatusLine`. Raised by `HTTPConnection.getresponse()` when the attempt to read the response results in no data read from the connection, indicating that the remote end has closed the connection.

  3.5 新版功能: Previously, `BadStatusLine``('')` was raised.

此模块中定义的常量为：

`http.client.``HTTP_PORT`

  The default port for the HTTP protocol (always `80`).

`http.client.``HTTPS_PORT`

  The default port for the HTTPS protocol (always `443`).

`http.client.``responses`

  This dictionary maps the HTTP 1.1 status codes to the W3C names.

  Example: `http.client.responses[http.client.NOT_FOUND]` is `'Not Found'`.

See HTTP 状态码 for a list of HTTP status codes that are available in this module as constants.

## HTTPConnection Objects

`HTTPConnection` instances have the following methods:

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

  This will send a request to the server using the HTTP request method method and the selector url.

  If body is specified, the specified data is sent after the headers are finished. It may be a `str`, a bytes-like object, an open file object, or an iterable of `bytes`. If body is a string, it is encoded as ISO-8859-1, the default for HTTP. If it is a bytes-like object, the bytes are sent as is. If it is a file object, the contents of the file is sent; this file object should support at least the `read()` method. If the file object is an instance of `io.TextIOBase`, the data returned by the `read()` method will be encoded as ISO-8859-1, otherwise the data returned by `read()` is sent as is. If body is an iterable, the elements of the iterable are sent as is until the iterable is exhausted.

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

  If headers contains neither Content-Length nor Transfer-Encoding, but there is a request body, one of those header fields will be added automatically. If body is `None`, the Content-Length header is set to `0` for methods that expect a body (`PUT`, `POST`, and `PATCH`). If body is a string or a bytes-like object that is not also a file, the Content-Length header is set to its length. Any other type of body (files and iterables in general) will be chunk-encoded, and the Transfer-Encoding header will automatically be set instead of Content-Length.

  The encode_chunked argument is only relevant if Transfer-Encoding is specified in headers. If encode_chunked is `False`, the HTTPConnection object assumes that all encoding is handled by the calling code. If it is `True`, the body will be chunk-encoded.

  注解

  Chunked transfer encoding has been added to the HTTP protocol version 1.1. Unless the HTTP server is known to handle HTTP 1.1, the caller must either specify the Content-Length, or must pass a `str` or bytes-like object that is not also a file as the body representation.

  3.2 新版功能: body can now be an iterable.

  在 3.6 版更改: If neither Content-Length nor Transfer-Encoding are set in headers, file and iterable body objects are now chunk-encoded. The encode_chunked argument was added. No attempt is made to determine the Content-Length for file objects.

`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`()

  Close the connection to the server.

`HTTPConnection.``blocksize`

  Buffer size in bytes for sending a file-like message body.

  3.7 新版功能.

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.abc.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.

## HTTPResponse Objects

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`

  Status code returned by server.

`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.

## 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 = http.client.HTTPSConnection("docs.python.org")
    >>> 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

## HTTPMessage Objects

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