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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.
.. data:: RETRIES
A request will be tried 'RETRIES' times if it fails at the socket/connection level.
The default is 2.
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], [proxy_info==ProxyInfo.from_environment], [ca_certs=None], [disable_ssl_certificate_validation=False])
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. The *ca_certs* parameter is the filename of the
CA certificates to use. If none is given a default set is used. The
*disable_ssl_certificate_validation* boolean flag determines if ssl certificate validation
is done. The *proxy_info* parameter is an object of type :class:`ProxyInfo`.
.. class:: ProxyInfo(proxy_type, proxy_host, proxy_port, [proxy_rdns=None], [proxy_user=None], [proxy_pass=None])
Collect information required to use a proxy.
The parameter proxy_type must be set to one of socks.PROXY_TYPE_XXX
constants. For example: ::
p = ProxyInfo(proxy_type=socks.PROXY_TYPE_HTTP, proxy_host='localhost', proxy_port=8000)
.. 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 an 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.forward_authorization_headers
If ``False``, which is the default, then Authorization: headers are
stripped from redirects. If ``True`` then Authorization: headers are left
in place when following redirects. This parameter only applies if following
redirects is turned on. Note that turning this on could cause your credentials
to leak, so carefully consider the consequences.
.. 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 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 responses.
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)