doc/libhttplib2.rst

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:mod:`httplib2`  A comprehensive HTTP client library.
=====================================================

.. module:: httplib2
.. moduleauthor:: Joe Gregorio <joe@bitworking.org>
.. sectionauthor:: Joe Gregorio <joe@bitworking.org>


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The :mod:`httplib2` module is a comprehensive HTTP client library with the
following features:

.. % ==== 2. ====
.. % Give a short overview of what the module does.
.. % If it is platform specific, mention this.
.. % Mention other important restrictions or general operating principles.
.. % For example:

.. describe:: HTTP and HTTPS

   HTTPS support is only available if the socket module was compiled with SSL
   support.

.. describe:: Keep-Alive

   Supports HTTP 1.1 Keep-Alive, keeping the socket open and performing multiple
   requests over the same connection if possible.

.. describe:: Authentication

   The following three types of HTTP Authentication are supported. These can be
   used over both HTTP and HTTPS.

      * Digest
      * Basic
      * WSSE

.. describe:: Caching

   The module can optionally operate with a private cache that understands the
   Cache-Control: header and uses both the ETag and Last-Modified cache validators.

.. describe:: All Methods

   The module can handle any HTTP request method, not just GET and POST.

.. describe:: Redirects

   Automatically follows 3XX redirects on GETs.

.. describe:: Compression

   Handles both ``deflate`` and ``gzip`` types of compression.

.. describe:: Lost update support

   Automatically adds back ETags into PUT requests to resources we have already
   cached. This implements Section 3.2 of Detecting the Lost Update Problem Using
   Unreserved Checkout

The :mod:`httplib2` module defines the following variables:

.. % ==== 3. ====
.. % List the public functions defined by the module.  Begin with a
.. % standard phrase.  You may also list the exceptions and other data
.. % items defined in the module, insofar as they are important for the
.. % user.
.. % ---- 3.2. ----
.. % Data items are described using a ``datadesc'' block.  This has only
.. % one parameter: the item's name.


.. data:: debuglevel

   The amount of debugging information to print. The default is 0.

The :mod:`httplib2` module may raise the following Exceptions. Note that  there
is an option that turns exceptions into  normal responses with an HTTP status
code indicating an error occured. See
:attr:`Http.force_exception_to_status_code`

.. % --- 3.3. ---
.. % Exceptions are described using a ``excdesc'' block.  This has only
.. % one parameter: the exception name.  Exceptions defined as classes in
.. % the source code should be documented using this environment, but
.. % constructor parameters must be omitted.


.. exception:: HttpLib2Error

   The Base Exception for all exceptions raised by httplib2.


.. exception:: RedirectMissingLocation

   A 3xx redirect response code was provided but no Location: header  was provided
   to point to the new location.


.. exception:: RedirectLimit

   The maximum number of redirections was reached without coming to a final URI.


.. exception:: ServerNotFoundError

   Unable to resolve the host name given.


.. exception:: RelativeURIError

   A relative, as opposed to an absolute URI, was passed into request().


.. exception:: FailedToDecompressContent

   The headers claimed that the content of the response was compressed but the
   decompression algorithm applied to the content failed.


.. exception:: UnimplementedDigestAuthOptionError

   The server requested a type of Digest authentication that we are unfamiliar
   with.


.. exception:: UnimplementedHmacDigestAuthOptionError

   The server requested a type of HMACDigest authentication that we are unfamiliar
   with.

.. % ---- 3.4. ----
.. % Other standard environments:
.. % 
.. % classdesc	- Python classes; same arguments are funcdesc
.. % methoddesc	- methods, like funcdesc but has an optional parameter
.. % to give the type name: \begin{methoddesc}[mytype]{name}{args}
.. % By default, the type name will be the name of the
.. % last class defined using classdesc.  The type name
.. % is required if the type is implemented in C (because
.. % there's no classdesc) or if the class isn't directly
.. % documented (if it's private).
.. % memberdesc	- data members, like datadesc, but with an optional
.. % type name like methoddesc.


.. class:: Http([cache=None], [timeout=None])

   The class that represents a client HTTP interface. The *cache* parameter is
   either the name of a directory to be used as a flat file cache, or it must an
   object that  implements the required caching interface. The *timeout* parameter
   is the socket level timeout.


.. class:: Response(info)

   Response is a subclass of :class:`dict` and instances of this  class are
   returned from calls to Http.request. The *info* parameter is either  an
   :class:`rfc822.Message` or an :class:`httplib.HTTPResponse` object.


.. class:: FileCache(dir_name, [safe=safename])

   FileCache implements a Cache as a directory of files. The *dir_name* parameter
   is the name of the directory to use. If the directory does not exist then
   FileCache attempts to create the directory. The optional *safe* parameter is a
   funtion which generates the cache filename for each URI. A FileCache object is
   constructed and used for caching when you pass a directory name into the
   constructor of :class:`Http`.

Http objects have the following methods:

.. % If your module defines new object types (for a built-in module) or
.. % classes (for a module written in Python), you should list the
.. % methods and instance variables (if any) of each type or class in a
.. % separate subsection.

.. _http-objects:

Http Objects
---------------

.. method:: Http.request(uri, [method="GET", body=None, headers=None, redirections=DEFAULT_MAX_REDIRECTS, connection_type=None])

   Performs a single HTTP request. The *uri* is the URI of the HTTP resource and
   can begin with either ``http`` or ``https``. The value of *uri* must be an
   absolute URI.

   The *method* is the HTTP method to perform, such as ``GET``, ``POST``,
   ``DELETE``, etc. There is no restriction on the methods allowed.

   The *body* is the entity body to be sent with the request. It is a string
   object.

   Any extra headers that are to be sent with the request should be provided in the
   *headers* dictionary.

   The maximum number of redirect to follow before raising an exception is
   *redirections*. The default is 5.

   The *connection_type* is the type of connection object to use. The supplied
   class should implement the interface of httplib.HTTPConnection.

   The return value is a tuple of (response, content), the first being and instance
   of the :class:`Response` class, the second being a string that contains the
   response entity body.


.. method:: Http.add_credentials(name, password, [domain=None])

   Adds a name and password that will be used when a request  requires
   authentication. Supplying the optional *domain* name will restrict these
   credentials to only be sent to the specified domain. If *domain* is not
   specified then the given credentials will be used to try to satisfy every HTTP
   401 challenge.


.. method:: Http.add_certificate(key, cert, domain)

   Add a *key* and *cert* that will be used for an SSL connection to the specified
   domain. *keyfile* is the name of a PEM formatted  file that contains your
   private key. *certfile* is a PEM formatted certificate chain file.


.. method:: Http.clear_credentials()

   Remove all the names and passwords used for authentication.


.. attribute:: Http.follow_redirects

   If ``True``, which is the default, safe redirects are followed, where safe means
   that the client is only doing a ``GET`` or ``HEAD`` on the URI to which it is
   being redirected. If ``False`` then no redirects are followed. Note that a False
   'follow_redirects' takes precedence over a True 'follow_all_redirects'. Another
   way of saying that is for 'follow_all_redirects' to have any affect,
   'follow_redirects' must be True.


.. attribute:: Http.follow_all_redirects

   If ``False``, which is the default, only safe redirects are followed, where safe
   means that the client is only doing a ``GET`` or ``HEAD`` on the URI to which it
   is being redirected. If ``True`` then all redirects are followed. Note that a
   False 'follow_redirects' takes precedence over a True 'follow_all_redirects'.
   Another way of saying that is for 'follow_all_redirects' to have any affect,
   'follow_redirects' must be True.


.. attribute:: Http.force_exception_to_status_code

   If ``True`` then no :mod:`httplib2` exceptions will be
   thrown. Instead, those error conditions will be turned into :class:`Response`
   objects that will be returned normally.

   If ``False``, which is the default, then exceptions will be thrown.


.. attribute:: Http.optimistic_concurrency_methods

   By default a list that only contains "PUT", this attribute
   controls which methods will get 'if-match' headers attached
   to them from cached responses with etags. You can append
   new items to this list to add new methods that should
   get this support, such as "PATCH".

.. attribute:: Http.ignore_etag

   Defaults to ``False``. If ``True``, then any etags present in the cached
   response are ignored when processing the current request, i.e. httplib2 does
   **not** use 'if-match' for PUT or 'if-none-match' when GET or HEAD requests are
   made. This is mainly to deal with broken servers which supply an etag, but
   change it capriciously.

If you wish to supply your own caching implementation then you will need to pass
in an object that supports the  following methods. Note that the :mod:`memcache`
module supports this interface natively.


.. _cache-objects:

Cache Objects
--------------

.. method:: Cache.get(key)

   Takes a string *key* and returns the value as a string.


.. method:: Cache.set(key, value)

   Takes a string *key* and *value* and stores it in the cache.


.. method:: Cache.delete(key)

   Deletes the cached value stored at *key*. The value of *key* is a string.

Response objects are derived from :class:`dict` and map header names (lower case
with the trailing colon removed) to header values. In addition to the dict
methods a Response object also has:


.. _response-objects:

Response Objects
------------------


.. attribute:: Response.fromcache

   If ``true`` the the response was returned from the cache.


.. attribute:: Response.version

   The version of HTTP that the server supports. A value of 11 means '1.1'.


.. attribute:: Response.status

   The numerical HTTP status code returned in the response.


.. attribute:: Response.reason

   The human readable component of the HTTP response status code.


.. attribute:: Response.previous

   If redirects are followed then the :class:`Response` object returned is just for
   the very last HTTP request and *previous* points to the previous
   :class:`Response` object. In this manner they form a chain going back through
   the responses to the very first response. Will be ``None`` if there are no
   previous respones.

The Response object also populates the header ``content-location``, that
contains the URI that was ultimately requested. This is useful if redirects were
encountered, you can determine the ultimate URI that the request was sent to.
All Response objects contain this key value, including ``previous`` responses so
you can determine the entire chain of redirects. If
:attr:`Http.force_exception_to_status_code` is ``True`` and the number of
redirects has exceeded the number of allowed number  of redirects then the
:class:`Response` object will report the error in the status code, but the
complete chain of previous responses will still be in tact.

To do a simple ``GET`` request just supply the absolute URI of the resource:

.. % ==== 4. ====
.. % Now is probably a good time for a complete example.  (Alternatively,
.. % an example giving the flavor of the module may be given before the
.. % detailed list of functions.)

.. _httplib2-example:

Examples
---------

::

   import httplib2
   h = httplib2.Http()
   resp, content = h.request("http://bitworking.org/")
   assert resp.status == 200
   assert resp['content-type'] == 'text/html'

Here is more complex example that does a PUT  of some text to a resource that
requires authentication. The Http instance also uses a file cache in the
directory ``.cache``.  ::

   import httplib2
   h = httplib2.Http(".cache")
   h.add_credentials('name', 'password')
   resp, content = h.request("https://example.org/chap/2", 
       "PUT", body="This is text", 
       headers={'content-type':'text/plain'} )

Here is an example that connects to a server that  supports the Atom Publishing
Protocol. ::

   import httplib2
   h = httplib2.Http()
   h.add_credentials(myname, mypasswd)
   h.follow_all_redirects = True
   headers = {'Content-Type': 'application/atom+xml'}
   body    = """<?xml version="1.0" ?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2003-12-13T18:30:02Z</updated>
         <author><name>John Doe</name></author>
         <content>Some text.</content>
   </entry>
   """
   uri     = "http://www.example.com/collection/"
   resp, content = h.request(uri, "POST", body=body, headers=headers)

Here is an example of providing data to an HTML form processor. In this case we
presume this is a POST form. We need to take our  data and format it as
"application/x-www-form-urlencoded" data and use that as a  body for a POST
request.


::

   >>> import httplib2
   >>> import urllib
   >>> data = {'name': 'fred', 'address': '123 shady lane'}
   >>> body = urllib.urlencode(data)
   >>> body
   'name=fred&address=123+shady+lane'
   >>> h = httplib2.Http()
   >>> resp, content = h.request("http://example.com", method="POST", body=body)