cpython_sandbox / Doc / library / xmlrpc.client.rst

:mod:`xmlrpc.client` --- XML-RPC client access

Source code: :source:`Lib/xmlrpc/client.py`


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.

Warning

The :mod:`xmlrpc.client` module is not secure against maliciously constructed data. If you need to parse untrusted or unauthenticated data see :ref:`xml-vulnerabilities`.

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` attribute:

A working example follows. The server code:

from xmlrpc.server 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 xmlrpc.client

proxy = xmlrpc.client.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 rich comparison and :meth:`__repr__` methods.

A working example follows. The server code:

import datetime
from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def today():
    today = datetime.datetime.today()
    return xmlrpc.client.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 xmlrpc.client
import datetime

proxy = xmlrpc.client.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 bytes 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 :meth:`__eq__` and :meth:`__ne__` methods.

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

from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def python_logo():
    with open("python_logo.jpg", "rb") as handle:
        return xmlrpc.client.Binary(handle.read())

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 xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
with open("fetched_python_logo.jpg", "wb") as handle:
    handle.write(proxy.python_logo().data)

Fault Objects

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

In the following example we're going to intentionally cause a :exc:`Fault` by returning a complex type object. The server code:

from xmlrpc.server 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 xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
try:
    proxy.add(2, 5)
except xmlrpc.client.Fault as err:
    print("A fault occurred")
    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 attributes:

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

import xmlrpc.client

# create a ServerProxy with an URI that doesn't respond to XMLRPC requests
proxy = xmlrpc.client.ServerProxy("http://google.com/")

try:
    proxy.some_method()
except xmlrpc.client.ProtocolError as err:
    print("A protocol error occurred")
    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

The :class:`MultiCall` object provides a way to encapsulate multiple calls to a remote server into a single request [1].

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 xmlrpc.server 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 xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
multicall = xmlrpc.client.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 xmlrpc.client 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 xmlrpc.client, http.client

class ProxiedTransport(xmlrpc.client.Transport):
    def set_proxy(self, proxy):
        self.proxy = proxy
    def make_connection(self, host):
        self.realhost = host
        h = http.client.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 = xmlrpc.client.Server('http://time.xmlrpc.com/RPC2', transport=p)
print(server.currentTime.getCurrentTime())

Example of Client and Server Usage

See :ref:`simplexmlrpcserver-example`.

Footnotes

[1]This approach has been first presented in a discussion on xmlrpc.com.
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