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` objects may be passed to calls.
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` 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:

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:
A working example follows. The server code:
import xmlrpclib
from SimpleXMLRPCServer import SimpleXMLRPCServer

def is_even(n):
    return n%2 == 0

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(is_even, "is_even")
server.serve_forever()

The client code for the preceding server:
import xmlrpclib

proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
print("3 is even: %s" % str(proxy.is_even(3)))
print("100 is even: %s" % str(proxy.is_even(100)))


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`
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.
A working example follows. The server code:
import datetime
from SimpleXMLRPCServer import SimpleXMLRPCServer
import xmlrpclib

def today():
    today = datetime.datetime.today()
    return xmlrpclib.DateTime(today)

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(today, "today")
server.serve_forever()

The client code for the preceding server:
import xmlrpclib
import datetime

proxy = xmlrpclib.ServerProxy("http://localhost:8000/")

today = proxy.today()
# convert the ISO8601 string to a datetime object
converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S")
print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))


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.
Example usage of the binary objects.  We're going to transfer an image over
XMLRPC:
from SimpleXMLRPCServer import SimpleXMLRPCServer
import xmlrpclib

def python_logo():
     handle = open("python_logo.jpg")
     return xmlrpclib.Binary(handle.read())
     handle.close()

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(python_logo, 'python_logo')

server.serve_forever()

The client gets the image and saves it to a file:
import xmlrpclib

proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
handle = open("fetched_python_logo.jpg", "w")
handle.write(proxy.python_logo().data)
handle.close()


Fault Objects
A :class:`Fault` object encapsulates the content of an XML-RPC fault tag. Fault
objects have the following members:
In the following example we're going to intentionally cause a :exc:`Fault` by
returning a complex type object.  The server code:
from SimpleXMLRPCServer import SimpleXMLRPCServer

# A marshalling error is going to occur because we're returning a
# complex number
def add(x,y):
    return x+y+0j

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(add, 'add')

server.serve_forever()

The client code for the preceding server:
import xmlrpclib

proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
try:
    proxy.add(2, 5)
except xmlrpclib.Fault, err:
    print("A fault occured")
    print("Fault code: %d" % err.faultCode)
    print("Fault string: %s" % err.faultString)


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:
In the following example we're going to intentionally cause a :exc:`ProtocolError`
by providing an invalid URI:
import xmlrpclib

# create a ServerProxy with an invalid URI
proxy = xmlrpclib.ServerProxy("http://invalidaddress/")

try:
    proxy.some_method()
except xmlrpclib.ProtocolError, err:
    print("A protocol error occured")
    print("URL: %s" % err.url)
    print("HTTP/HTTPS headers: %s" % err.headers)
    print("Error code: %d" % err.errcode)
    print("Error message: %s" % err.errmsg)


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 :term:`generator`; iterating over this generator yields the individual
results.
A usage example of this class follows.  The server code
from SimpleXMLRPCServer import SimpleXMLRPCServer

def add(x,y):
    return x+y

def subtract(x, y):
    return x-y

def multiply(x, y):
    return x*y

def divide(x, y):
    return x/y

# A simple server with simple arithmetic functions
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_multicall_functions()
server.register_function(add, 'add')
server.register_function(subtract, 'subtract')
server.register_function(multiply, 'multiply')
server.register_function(divide, 'divide')
server.serve_forever()

The client code for the preceding server:
import xmlrpclib

proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
multicall = xmlrpclib.MultiCall(proxy)
multicall.add(7,3)
multicall.subtract(7,3)
multicall.multiply(7,3)
multicall.divide(7,3)
result = multicall()

print("7+3=%d, 7-3=%d, 7*3=%d, 7/3=%d" % tuple(result))


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 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())


Example of Client and Server Usage
See :ref:`simplexmlrpcserver-example`.