= Problem =

You want to provide an interface into your application that can be used by other
programs.  For example, a bug tracking system could support some way 
for users to write scripts that retrieve the list of bugs assigned to them.

= Solution =

Write an XML-RPC interface.  Quixote includes a helper function in the `quixote.util` 
module that simplifies the task.

{{{
from quixote.util import xmlrpc

def rpc (request, rpc_process):
    return xmlrpc(request, rpc_process)

def rpc_process (meth, params):
    if meth == 'list_bugs':
        user, password = params
        return retrieve_bugs_for_user(user, password)
    else:
        raise RuntimeError, "Unknown XML-RPC method: %r" % meth
}}}

To call the interface implemented above from a Python script, you would use 
the following code:

{{{
import xmlrpclib
s = xmlrpclib.Server('http://your.server.example.com/rpc')
bugs = s.list_bugs('amk', 'password')
}}}

XML-RPC implementations are available for most other languages, so the `list_bugs()` method 
could be called from any of them.

= Discussion =

XML-RPC's data types are relatively limited.  You can return numbers, strings, lists, and dictionaries.  
You can't return Python objects, complex numbers,or Python's `None` value (the most irritating omission). 

Consult the [[http://www.mems-exchange.org/software/quixote/doc/web-services.html|web-services.txt]] 
documentation file included with Quixote for more information about implementing XML-RPC interfaces.

The 'RPC' stands for Remote Procedure Call, since you're basically providing a way to call 
a function on your server.
[[http://internet.conveyor.com/RESTwiki/moin.cgi/FrontPage|REST]] is a competing application design approach 
that uses URLs to represent operations and queries, and therefore has certain nice properties.  For example, if you have a URL representing "amk's bug list", this URL can be bookmarked, forwarded to other people, and have RDF assertions made about it, 
none of which are possible with XML-RPC queries.


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CategoryCookbook