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cpython/Doc/library/http.client.rst
Christian Heimes f97406be4c
bpo-40968: Send http/1.1 ALPN extension (#20959) 
Signed-off-by: Christian Heimes <christian@python.org>
2020-11-13 16:37:52 +01:00

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:mod:`http.client` --- HTTP protocol client
===========================================
.. module:: http.client
:synopsis: HTTP and HTTPS protocol client (requires sockets).
**Source code:** :source:`Lib/http/client.py`
.. index::
pair: HTTP; protocol
single: HTTP; http.client (standard module)
.. index:: module: urllib.request
--------------
This module defines classes which implement the client side of the HTTP and
HTTPS protocols. It is normally not used directly --- the module
:mod:`urllib.request` uses it to handle URLs that use HTTP and HTTPS.
.. seealso::
The `Requests package <https://requests.readthedocs.io/en/master/>`_
is recommended for a higher-level HTTP client interface.
.. note::
HTTPS support is only available if Python was compiled with SSL support
(through the :mod:`ssl` module).
The module provides the following classes:
.. class:: HTTPConnection(host, port=None[, timeout], source_address=None, \
blocksize=8192)
An :class:`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.
The optional *blocksize* parameter sets the buffer size in bytes for
sending a file-like message body.
For example, the following calls all create instances that connect to the server
at the same host and port::
>>> 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)
.. versionchanged:: 3.2
*source_address* was added.
.. versionchanged:: 3.4
The *strict* parameter was removed. HTTP 0.9-style "Simple Responses" are
not longer supported.
.. versionchanged:: 3.7
*blocksize* parameter was added.
.. class:: HTTPSConnection(host, port=None, key_file=None, \
cert_file=None[, timeout], \
source_address=None, *, context=None, \
check_hostname=None, blocksize=8192)
A subclass of :class:`HTTPConnection` that uses SSL for communication with
secure servers. Default port is ``443``. If *context* is specified, it
must be a :class:`ssl.SSLContext` instance describing the various SSL
options.
Please read :ref:`ssl-security` for more information on best practices.
.. versionchanged:: 3.2
*source_address*, *context* and *check_hostname* were added.
.. versionchanged:: 3.2
This class now supports HTTPS virtual hosts if possible (that is,
if :data:`ssl.HAS_SNI` is true).
.. versionchanged:: 3.4
The *strict* parameter was removed. HTTP 0.9-style "Simple Responses" are
no longer supported.
.. versionchanged:: 3.4.3
This class now performs all the necessary certificate and hostname checks
by default. To revert to the previous, unverified, behavior
:func:`ssl._create_unverified_context` can be passed to the *context*
parameter.
.. versionchanged:: 3.8
This class now enables TLS 1.3
:attr:`ssl.SSLContext.post_handshake_auth` for the default *context* or
when *cert_file* is passed with a custom *context*.
.. versionchanged:: 3.10
This class now sends an ALPN extension with protocol indicator
``http/1.1`` when no *context* is given. Custom *context* should set
ALPN protocols with :meth:`~ssl.SSLContext.set_alpn_protocol`.
.. deprecated:: 3.6
*key_file* and *cert_file* are deprecated in favor of *context*.
Please use :meth:`ssl.SSLContext.load_cert_chain` instead, or let
:func:`ssl.create_default_context` select the system's trusted CA
certificates for you.
The *check_hostname* parameter is also deprecated; the
:attr:`ssl.SSLContext.check_hostname` attribute of *context* should
be used instead.
.. class:: HTTPResponse(sock, debuglevel=0, method=None, url=None)
Class whose instances are returned upon successful connection. Not
instantiated directly by user.
.. versionchanged:: 3.4
The *strict* parameter was removed. HTTP 0.9 style "Simple Responses" are
no longer supported.
This module provides the following function:
.. function:: parse_headers(fp)
Parse the headers from a file pointer *fp* representing a HTTP
request/response. The file has to be a :class:`BufferedIOBase` reader
(i.e. not text) and must provide a valid :rfc:`2822` style header.
This function returns an instance of :class:`http.client.HTTPMessage`
that holds the header fields, but no payload
(the same as :attr:`HTTPResponse.msg`
and :attr:`http.server.BaseHTTPRequestHandler.headers`).
After returning, the file pointer *fp* is ready to read the HTTP body.
.. note::
:meth:`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.
The following exceptions are raised as appropriate:
.. exception:: HTTPException
The base class of the other exceptions in this module. It is a subclass of
:exc:`Exception`.
.. exception:: NotConnected
A subclass of :exc:`HTTPException`.
.. exception:: InvalidURL
A subclass of :exc:`HTTPException`, raised if a port is given and is either
non-numeric or empty.
.. exception:: UnknownProtocol
A subclass of :exc:`HTTPException`.
.. exception:: UnknownTransferEncoding
A subclass of :exc:`HTTPException`.
.. exception:: UnimplementedFileMode
A subclass of :exc:`HTTPException`.
.. exception:: IncompleteRead
A subclass of :exc:`HTTPException`.
.. exception:: ImproperConnectionState
A subclass of :exc:`HTTPException`.
.. exception:: CannotSendRequest
A subclass of :exc:`ImproperConnectionState`.
.. exception:: CannotSendHeader
A subclass of :exc:`ImproperConnectionState`.
.. exception:: ResponseNotReady
A subclass of :exc:`ImproperConnectionState`.
.. exception:: BadStatusLine
A subclass of :exc:`HTTPException`. Raised if a server responds with a HTTP
status code that we don't understand.
.. exception:: LineTooLong
A subclass of :exc:`HTTPException`. Raised if an excessively long line
is received in the HTTP protocol from the server.
.. exception:: RemoteDisconnected
A subclass of :exc:`ConnectionResetError` and :exc:`BadStatusLine`. Raised
by :meth:`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.
.. versionadded:: 3.5
Previously, :exc:`BadStatusLine`\ ``('')`` was raised.
The constants defined in this module are:
.. data:: HTTP_PORT
The default port for the HTTP protocol (always ``80``).
.. data:: HTTPS_PORT
The default port for the HTTPS protocol (always ``443``).
.. data:: 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 :ref:`http-status-codes` for a list of HTTP status codes that are
available in this module as constants.
.. _httpconnection-objects:
HTTPConnection Objects
----------------------
:class:`HTTPConnection` instances have the following methods:
.. method:: 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 :class:`str`, a :term:`bytes-like object`, an
open :term:`file object`, or an iterable of :class:`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 :term:`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 :class:`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
:term:`file <file object>`, 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.
.. note::
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
:class:`str` or bytes-like object that is not also a file as the
body representation.
.. versionadded:: 3.2
*body* can now be an iterable.
.. versionchanged:: 3.6
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.
.. method:: HTTPConnection.getresponse()
Should be called after a request is sent to get the response from the server.
Returns an :class:`HTTPResponse` instance.
.. note::
Note that you must have read the whole response before you can send a new
request to the server.
.. versionchanged:: 3.5
If a :exc:`ConnectionError` or subclass is raised, the
:class:`HTTPConnection` object will be ready to reconnect when
a new request is sent.
.. method:: 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 :class:`HTTPResponse` objects that are created.
.. versionadded:: 3.1
.. method:: 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 :class:`HTTPSConnection`
constructor, and the address of the host that we eventually want to reach to
the :meth:`~HTTPConnection.set_tunnel` method::
>>> import http.client
>>> conn = http.client.HTTPSConnection("localhost", 8080)
>>> conn.set_tunnel("www.python.org")
>>> conn.request("HEAD","/index.html")
.. versionadded:: 3.2
.. method:: 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.
.. method:: HTTPConnection.close()
Close the connection to the server.
.. attribute:: HTTPConnection.blocksize
Buffer size in bytes for sending a file-like message body.
.. versionadded:: 3.7
As an alternative to using the :meth:`request` method described above, you can
also send your request step by step, by using the four functions below.
.. method:: 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.
.. method:: 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.
.. method:: 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 :ref:`buffer interface
<bufferobjects>` the encoding will result in a single chunk.
If *message_body* is a :class:`collections.abc.Iterable`, each iteration
of *message_body* will result in a chunk. If *message_body* is a
:term:`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*.
.. note:: 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.
.. versionadded:: 3.6
Chunked encoding support. The *encode_chunked* parameter was
added.
.. method:: HTTPConnection.send(data)
Send data to the server. This should be used directly only after the
:meth:`endheaders` method has been called and before :meth:`getresponse` is
called.
.. _httpresponse-objects:
HTTPResponse Objects
--------------------
An :class:`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.
.. versionchanged:: 3.5
The :class:`io.BufferedIOBase` interface is now implemented and
all of its reader operations are supported.
.. method:: HTTPResponse.read([amt])
Reads and returns the response body, or up to the next *amt* bytes.
.. method:: 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.
.. versionadded:: 3.3
.. method:: 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.
.. method:: HTTPResponse.getheaders()
Return a list of (header, value) tuples.
.. method:: HTTPResponse.fileno()
Return the ``fileno`` of the underlying socket.
.. attribute:: HTTPResponse.msg
A :class:`http.client.HTTPMessage` instance containing the response
headers. :class:`http.client.HTTPMessage` is a subclass of
:class:`email.message.Message`.
.. attribute:: HTTPResponse.version
HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1.
.. attribute:: HTTPResponse.url
URL of the resource retrieved, commonly used to determine if a redirect was followed.
.. attribute:: HTTPResponse.headers
Headers of the response in the form of an :class:`email.message.EmailMessage` instance.
.. attribute:: HTTPResponse.status
Status code returned by server.
.. attribute:: HTTPResponse.reason
Reason phrase returned by server.
.. attribute:: HTTPResponse.debuglevel
A debugging hook. If :attr:`debuglevel` is greater than zero, messages
will be printed to stdout as the response is read and parsed.
.. attribute:: HTTPResponse.closed
Is ``True`` if the stream is closed.
.. method:: HTTPResponse.geturl()
.. deprecated:: 3.9
Deprecated in favor of :attr:`~HTTPResponse.url`.
.. method:: HTTPResponse.info()
.. deprecated:: 3.9
Deprecated in favor of :attr:`~HTTPResponse.headers`.
.. method:: HTTPResponse.getstatus()
.. deprecated:: 3.9
Deprecated in favor of :attr:`~HTTPResponse.status`.
Examples
--------
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 chunk := r1.read(200):
... print(repr(chunk))
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 :class:`urllib.request.Request` by setting the appropriate
method attribute. Here is an example session that shows how to send a ``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:
HTTPMessage Objects
-------------------
An :class:`http.client.HTTPMessage` instance holds the headers from an HTTP
response. It is implemented using the :class:`email.message.Message` class.
.. XXX Define the methods that clients can depend upon between versions.
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