21.12. "http.client" — HTTP protocol client
*******************************************

**Source code:** Lib/http/client.py

======================================================================

This module defines classes which implement the client side of the
HTTP and HTTPS protocols.  It is normally not used directly — the
module "urllib.request" uses it to handle URLs that use HTTP and
HTTPS.

See also: The Requests package is recommended for a higher-level
  HTTP client interface.

Note: HTTPS support is only available if Python was compiled with
  SSL support (through the "ssl" module).

The module provides the following classes:

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.

   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)

   Changed in version 3.2: *source_address* was added.

   Changed in version 3.4: The  *strict* parameter was removed. HTTP
   0.9-style “Simple Responses” are not longer supported.

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

   A subclass of "HTTPConnection" that uses SSL for communication with
   secure servers.  Default port is "443".  If *context* is specified,
   it must be a "ssl.SSLContext" instance describing the various SSL
   options.

   Please read Security considerations for more information on best
   practices.

   Changed in version 3.2: *source_address*, *context* and
   *check_hostname* were added.

   Changed in version 3.2: This class now supports HTTPS virtual hosts
   if possible (that is, if "ssl.HAS_SNI" is true).

   Changed in version 3.4: The *strict* parameter was removed. HTTP
   0.9-style “Simple Responses” are no longer supported.

   Changed in version 3.4.3: This class now performs all the necessary
   certificate and hostname checks by default. To revert to the
   previous, unverified, behavior "ssl._create_unverified_context()"
   can be passed to the *context* parameter.

   Deprecated since version 3.6: *key_file* and *cert_file* are
   deprecated in favor of *context*. Please use
   "ssl.SSLContext.load_cert_chain()" instead, or let
   "ssl.create_default_context()" select the system’s trusted CA
   certificates for you.The *check_hostname* parameter is also
   deprecated; the "ssl.SSLContext.check_hostname" attribute of
   *context* should be used instead.

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

   Class whose instances are returned upon successful connection.  Not
   instantiated directly by user.

   Changed in version 3.4: The *strict* parameter was removed. HTTP
   0.9 style “Simple Responses” are no longer supported.

The following exceptions are raised as appropriate:

exception http.client.HTTPException

   The base class of the other exceptions in this module.  It is a
   subclass of "Exception".

exception http.client.NotConnected

   A subclass of "HTTPException".

exception http.client.InvalidURL

   A subclass of "HTTPException", raised if a port is given and is
   either non-numeric or empty.

exception http.client.UnknownProtocol

   A subclass of "HTTPException".

exception http.client.UnknownTransferEncoding

   A subclass of "HTTPException".

exception http.client.UnimplementedFileMode

   A subclass of "HTTPException".

exception http.client.IncompleteRead

   A subclass of "HTTPException".

exception http.client.ImproperConnectionState

   A subclass of "HTTPException".

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.

   New in version 3.5: Previously, "BadStatusLine""('')" was raised.

The constants defined in this module are:

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


21.12.1. 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.

   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 "str" or bytes-like object that is not also a file as
     the body representation.

   New in version 3.2: *body* can now be an iterable.

   Changed in version 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.

HTTPConnection.getresponse()

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

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

   Changed in version 3.5: 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.

   New in version 3.1.

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")

   New in version 3.2.

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.

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*.

   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.

   New in version 3.6: 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 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.

Changed in version 3.5: 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.

   New in version 3.3.

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.


21.12.3. 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 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.
