cpython/Doc/library/xmlrpclib.rst

425 lines
17 KiB
ReStructuredText
Raw Normal View History

2007-08-15 11:28:01 -03:00
:mod:`xmlrpclib` --- XML-RPC client access
==========================================
.. module:: xmlrpclib
:synopsis: XML-RPC client access.
.. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com>
.. sectionauthor:: Eric S. Raymond <esr@snark.thyrsus.com>
.. % Not everything is documented yet. It might be good to describe
.. % Marshaller, Unmarshaller, getparser, dumps, loads, and Transport.
.. versionadded:: 2.2
XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP as a
transport. With it, a client can call methods with parameters on a remote
server (the server is named by a URI) and get back structured data. This module
supports writing XML-RPC client code; it handles all the details of translating
between conformable Python objects and XML on the wire.
.. class:: ServerProxy(uri[, transport[, encoding[, verbose[, allow_none[, use_datetime]]]]])
A :class:`ServerProxy` instance is an object that manages communication with a
remote XML-RPC server. The required first argument is a URI (Uniform Resource
Indicator), and will normally be the URL of the server. The optional second
argument is a transport factory instance; by default it is an internal
:class:`SafeTransport` instance for https: URLs and an internal HTTP
:class:`Transport` instance otherwise. The optional third argument is an
encoding, by default UTF-8. The optional fourth argument is a debugging flag.
If *allow_none* is true, the Python constant ``None`` will be translated into
XML; the default behaviour is for ``None`` to raise a :exc:`TypeError`. This is
a commonly-used extension to the XML-RPC specification, but isn't supported by
all clients and servers; see http://ontosys.com/xml-rpc/extensions.php for a
description. The *use_datetime* flag can be used to cause date/time values to
be presented as :class:`datetime.datetime` objects; this is false by default.
:class:`datetime.datetime`, :class:`datetime.date` and :class:`datetime.time`
objects may be passed to calls. :class:`datetime.date` objects are converted
with a time of "00:00:00". :class:`datetime.time` objects are converted using
today's date.
Both the HTTP and HTTPS transports support the URL syntax extension for HTTP
Basic Authentication: ``http://user:pass@host:port/path``. The ``user:pass``
portion will be base64-encoded as an HTTP 'Authorization' header, and sent to
the remote server as part of the connection process when invoking an XML-RPC
method. You only need to use this if the remote server requires a Basic
Authentication user and password.
The returned instance is a proxy object with methods that can be used to invoke
corresponding RPC calls on the remote server. If the remote server supports the
introspection API, the proxy can also be used to query the remote server for the
methods it supports (service discovery) and fetch other server-associated
metadata.
:class:`ServerProxy` instance methods take Python basic types and objects as
arguments and return Python basic types and classes. Types that are conformable
(e.g. that can be marshalled through XML), include the following (and except
where noted, they are unmarshalled as the same Python type):
+---------------------------------+---------------------------------------------+
| Name | Meaning |
+=================================+=============================================+
| :const:`boolean` | The :const:`True` and :const:`False` |
| | constants |
+---------------------------------+---------------------------------------------+
| :const:`integers` | Pass in directly |
+---------------------------------+---------------------------------------------+
| :const:`floating-point numbers` | Pass in directly |
+---------------------------------+---------------------------------------------+
| :const:`strings` | Pass in directly |
+---------------------------------+---------------------------------------------+
| :const:`arrays` | Any Python sequence type containing |
| | conformable elements. Arrays are returned |
| | as lists |
+---------------------------------+---------------------------------------------+
| :const:`structures` | A Python dictionary. Keys must be strings, |
| | values may be any conformable type. Objects |
| | of user-defined classes can be passed in; |
| | only their *__dict__* attribute is |
| | transmitted. |
+---------------------------------+---------------------------------------------+
| :const:`dates` | in seconds since the epoch (pass in an |
| | instance of the :class:`DateTime` class) or |
| | a :class:`datetime.datetime`, |
| | :class:`datetime.date` or |
| | :class:`datetime.time` instance |
+---------------------------------+---------------------------------------------+
| :const:`binary data` | pass in an instance of the :class:`Binary` |
| | wrapper class |
+---------------------------------+---------------------------------------------+
This is the full set of data types supported by XML-RPC. Method calls may also
raise a special :exc:`Fault` instance, used to signal XML-RPC server errors, or
:exc:`ProtocolError` used to signal an error in the HTTP/HTTPS transport layer.
Both :exc:`Fault` and :exc:`ProtocolError` derive from a base class called
:exc:`Error`. Note that even though starting with Python 2.2 you can subclass
builtin types, the xmlrpclib module currently does not marshal instances of such
subclasses.
When passing strings, characters special to XML such as ``<``, ``>``, and ``&``
will be automatically escaped. However, it's the caller's responsibility to
ensure that the string is free of characters that aren't allowed in XML, such as
the control characters with ASCII values between 0 and 31 (except, of course,
tab, newline and carriage return); failing to do this will result in an XML-RPC
request that isn't well-formed XML. If you have to pass arbitrary strings via
XML-RPC, use the :class:`Binary` wrapper class described below.
:class:`Server` is retained as an alias for :class:`ServerProxy` for backwards
compatibility. New code should use :class:`ServerProxy`.
.. versionchanged:: 2.5
The *use_datetime* flag was added.
.. versionchanged:: 2.6
2007-10-21 09:15:05 -03:00
Instances of :term:`new-style class`\es can be passed in if they have an
*__dict__* attribute and don't have a base class that is marshalled in a
special way.
2007-08-15 11:28:01 -03:00
.. seealso::
`XML-RPC HOWTO <http://www.tldp.org/HOWTO/XML-RPC-HOWTO/index.html>`_
A good description of XML operation and client software in several languages.
Contains pretty much everything an XML-RPC client developer needs to know.
`XML-RPC Hacks page <http://xmlrpc-c.sourceforge.net/hacks.php>`_
Extensions for various open-source libraries to support introspection and
multicall.
.. _serverproxy-objects:
ServerProxy Objects
-------------------
A :class:`ServerProxy` instance has a method corresponding to each remote
procedure call accepted by the XML-RPC server. Calling the method performs an
RPC, dispatched by both name and argument signature (e.g. the same method name
can be overloaded with multiple argument signatures). The RPC finishes by
returning a value, which may be either returned data in a conformant type or a
:class:`Fault` or :class:`ProtocolError` object indicating an error.
Servers that support the XML introspection API support some common methods
grouped under the reserved :attr:`system` member:
.. method:: ServerProxy.system.listMethods()
This method returns a list of strings, one for each (non-system) method
supported by the XML-RPC server.
.. method:: ServerProxy.system.methodSignature(name)
This method takes one parameter, the name of a method implemented by the XML-RPC
server.It returns an array of possible signatures for this method. A signature
is an array of types. The first of these types is the return type of the method,
the rest are parameters.
Because multiple signatures (ie. overloading) is permitted, this method returns
a list of signatures rather than a singleton.
Signatures themselves are restricted to the top level parameters expected by a
method. For instance if a method expects one array of structs as a parameter,
and it returns a string, its signature is simply "string, array". If it expects
three integers and returns a string, its signature is "string, int, int, int".
If no signature is defined for the method, a non-array value is returned. In
Python this means that the type of the returned value will be something other
that list.
.. method:: ServerProxy.system.methodHelp(name)
This method takes one parameter, the name of a method implemented by the XML-RPC
server. It returns a documentation string describing the use of that method. If
no such string is available, an empty string is returned. The documentation
string may contain HTML markup.
Introspection methods are currently supported by servers written in PHP, C and
Microsoft .NET. Partial introspection support is included in recent updates to
UserLand Frontier. Introspection support for Perl, Python and Java is available
at the `XML-RPC Hacks <http://xmlrpc-c.sourceforge.net/hacks.php>`_ page.
.. _boolean-objects:
Boolean Objects
---------------
This class may be initialized from any Python value; the instance returned
depends only on its truth value. It supports various Python operators through
:meth:`__cmp__`, :meth:`__repr__`, :meth:`__int__`, and :meth:`__nonzero__`
methods, all implemented in the obvious ways.
It also has the following method, supported mainly for internal use by the
unmarshalling code:
.. method:: Boolean.encode(out)
Write the XML-RPC encoding of this Boolean item to the out stream object.
.. _datetime-objects:
DateTime Objects
----------------
This class may be initialized with seconds since the epoch, a time tuple, an ISO
8601 time/date string, or a :class:`datetime.datetime`, :class:`datetime.date`
or :class:`datetime.time` instance. It has the following methods, supported
mainly for internal use by the marshalling/unmarshalling code:
.. method:: DateTime.decode(string)
Accept a string as the instance's new time value.
.. method:: DateTime.encode(out)
Write the XML-RPC encoding of this :class:`DateTime` item to the *out* stream
object.
It also supports certain of Python's built-in operators through :meth:`__cmp__`
and :meth:`__repr__` methods.
.. _binary-objects:
Binary Objects
--------------
This class may be initialized from string data (which may include NULs). The
primary access to the content of a :class:`Binary` object is provided by an
attribute:
.. attribute:: Binary.data
The binary data encapsulated by the :class:`Binary` instance. The data is
provided as an 8-bit string.
:class:`Binary` objects have the following methods, supported mainly for
internal use by the marshalling/unmarshalling code:
.. method:: Binary.decode(string)
Accept a base64 string and decode it as the instance's new data.
.. method:: Binary.encode(out)
Write the XML-RPC base 64 encoding of this binary item to the out stream object.
It also supports certain of Python's built-in operators through a
:meth:`__cmp__` method.
.. _fault-objects:
Fault Objects
-------------
A :class:`Fault` object encapsulates the content of an XML-RPC fault tag. Fault
objects have the following members:
.. attribute:: Fault.faultCode
A string indicating the fault type.
.. attribute:: Fault.faultString
A string containing a diagnostic message associated with the fault.
.. _protocol-error-objects:
ProtocolError Objects
---------------------
A :class:`ProtocolError` object describes a protocol error in the underlying
transport layer (such as a 404 'not found' error if the server named by the URI
does not exist). It has the following members:
.. attribute:: ProtocolError.url
The URI or URL that triggered the error.
.. attribute:: ProtocolError.errcode
The error code.
.. attribute:: ProtocolError.errmsg
The error message or diagnostic string.
.. attribute:: ProtocolError.headers
A string containing the headers of the HTTP/HTTPS request that triggered the
error.
MultiCall Objects
-----------------
.. versionadded:: 2.4
In http://www.xmlrpc.com/discuss/msgReader%241208, an approach is presented to
encapsulate multiple calls to a remote server into a single request.
.. class:: MultiCall(server)
Create an object used to boxcar method calls. *server* is the eventual target of
the call. Calls can be made to the result object, but they will immediately
return ``None``, and only store the call name and parameters in the
:class:`MultiCall` object. Calling the object itself causes all stored calls to
be transmitted as a single ``system.multicall`` request. The result of this call
2007-10-21 07:52:38 -03:00
is a :term:`generator`; iterating over this generator yields the individual
results.
2007-08-15 11:28:01 -03:00
A usage example of this class is ::
multicall = MultiCall(server_proxy)
multicall.add(2,3)
multicall.get_address("Guido")
add_result, address = multicall()
Convenience Functions
---------------------
.. function:: boolean(value)
Convert any Python value to one of the XML-RPC Boolean constants, ``True`` or
``False``.
.. function:: dumps(params[, methodname[, methodresponse[, encoding[, allow_none]]]])
Convert *params* into an XML-RPC request. or into a response if *methodresponse*
is true. *params* can be either a tuple of arguments or an instance of the
:exc:`Fault` exception class. If *methodresponse* is true, only a single value
can be returned, meaning that *params* must be of length 1. *encoding*, if
supplied, is the encoding to use in the generated XML; the default is UTF-8.
Python's :const:`None` value cannot be used in standard XML-RPC; to allow using
it via an extension, provide a true value for *allow_none*.
.. function:: loads(data[, use_datetime])
Convert an XML-RPC request or response into Python objects, a ``(params,
methodname)``. *params* is a tuple of argument; *methodname* is a string, or
``None`` if no method name is present in the packet. If the XML-RPC packet
represents a fault condition, this function will raise a :exc:`Fault` exception.
The *use_datetime* flag can be used to cause date/time values to be presented as
:class:`datetime.datetime` objects; this is false by default. Note that even if
you call an XML-RPC method with :class:`datetime.date` or :class:`datetime.time`
objects, they are converted to :class:`DateTime` objects internally, so only
:class:`datetime.datetime` objects will be returned.
.. versionchanged:: 2.5
The *use_datetime* flag was added.
.. _xmlrpc-client-example:
Example of Client Usage
-----------------------
::
# simple test program (from the XML-RPC specification)
from xmlrpclib import ServerProxy, Error
# server = ServerProxy("http://localhost:8000") # local server
server = ServerProxy("http://betty.userland.com")
print server
try:
print server.examples.getStateName(41)
except Error, v:
print "ERROR", v
To access an XML-RPC server through a proxy, you need to define a custom
transport. The following example, written by NoboNobo, shows how:
.. % fill in original author's name if we ever learn it
.. % Example taken from http://lowlife.jp/nobonobo/wiki/xmlrpcwithproxy.html
::
import xmlrpclib, httplib
class ProxiedTransport(xmlrpclib.Transport):
def set_proxy(self, proxy):
self.proxy = proxy
def make_connection(self, host):
self.realhost = host
h = httplib.HTTP(self.proxy)
return h
def send_request(self, connection, handler, request_body):
connection.putrequest("POST", 'http://%s%s' % (self.realhost, handler))
def send_host(self, connection, host):
connection.putheader('Host', self.realhost)
p = ProxiedTransport()
p.set_proxy('proxy-server:8080')
server = xmlrpclib.Server('http://time.xmlrpc.com/RPC2', transport=p)
print server.currentTime.getCurrentTime()