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sphinx / Doc-3k / library / xmlrpclib.rst

:mod:`xmlrpclib` --- XML-RPC client access

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.

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`.

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:

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 page.

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:`__bool__` methods, all implemented in the obvious ways.

It also has the following method, supported mainly for internal use by the unmarshalling code:

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:

It also supports certain of Python's built-in operators through :meth:`__cmp__` and :meth:`__repr__` methods.

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:

:class:`Binary` objects have the following methods, supported mainly for internal use by the marshalling/unmarshalling code:

It also supports certain of Python's built-in operators through a :meth:`__cmp__` method.

Fault Objects

A :class:`Fault` object encapsulates the content of an XML-RPC fault tag. Fault objects have the following members:

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:

MultiCall Objects

In http://www.xmlrpc.com/discuss/msgReader%241208, an approach is presented to encapsulate multiple calls to a remote server into a single request.

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 is a generator; iterating over this generator yields the individual results.

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

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 as 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:

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()
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