Python Cookbook 2Nd Edition Jun 1002005 [Electronic resources] نسخه متنی

Recipe 15.1. Making an XML-RPC Method Call

Credit: Rael Dornfest, Jeremy
Hylton

Problem

You need to make a method call to an XML-RPC server.

Solution

The xmlrpclib module makes writing XML-RPC clients
very easy. For example, we can use XML-RPC to access
O'Reilly's Meerkat server and get
the five most recent items about Python:

from xmlrpclib import Server
server = Server("http://www.oreillynet.com/meerkat/xml-rpc/server.php")
print server.meerkat.getItems(
{'search': '[Pp]ython', 'num_items': 5, 'descriptions': 0}
)

Discussion

XML-RPC is a simple, lightweight approach to distributed processing.
xmlrpclib, which makes it easy to write XML-RPC
clients in Python, is part of the Python Standard Library.

To use
xmlrpclib, you first instantiate a proxy to the
server, calling the ServerProxy class (also known
by the name Server) and passing in the URL to
which you want to connect. Then, on that proxy instance, you can
access and call whatever methods the remote XML-RPC server supplies.
In this case, you know that Meerkat supplies a
getItems method, so you call the method of the
same name on the server proxy instance. The proxy relays the call to
the server, waits for the server to respond, and finally returns the
call's results.

This recipe
uses O'Reilly's Meerkat service,
intended for syndication of contents such as news and product
announcements. Specifically, the recipe queries Meerkat for the five
most recent items mentioning either
"Python" or
"python". If you try this recipe,
be warned that response times from Meerkat are variable, depending on
the quality of your Internet connection, the time of day, and the
level of traffic on the Internet. If the script takes a long time to
answer, it doesn't mean you did something
wrongit just means you have to be patient!

Using xmlrpclib by passing raw dictionaries, as in
this recipe's code, is quite workable but somewhat
unPythonic. Here's an easy alternative that looks
nicer:

from xmlrpclib import Server
server = Server("http://www.oreillynet.com/meerkat/xml-rpc/server.php")
class MeerkatQuery(object):
def _ _init_ _(self, search, num_items=5, descriptions=0):
self.search = search
self.num_items = num_items
self.descriptions = descriptions
q = MeerkatQuery("[Pp]ython")
print server.meerkat.getItems(q)

You can package the instance attributes and their default values in
several different ways, but the main point of this variant is that,
as the argument to the getItems method, an
instance object with the right attributes works just as well as a
dictionary object with the same information packaged as dictionary
items.

See Also

The xmlrpclib module is part of the Python
Standard Library and is well documented in its chapter of the
Library Reference portion of
Python's online documentation. Meerkat is at
http://www.oreillynet.com/meerkat/.