\section{\module{xmlrpclib} --- XML-RPC client access} \declaremodule{standard}{xmlrpclib}\modulesynopsis{XML-RPC client access.}\moduleauthor{Fredrik Lundh}{fredrik@pythonware.com}\sectionauthor{Eric S. Raymond}{esr@snark.thyrsus.com} % Not everything is documented yet.  It might be good to describe % Marshaller, Unmarshaller, getparser, dumps, loads, and Transport. \versionadded{2.2} XML-RPC is a Remote Procedure Call method that uses XML passed viaHTTP as a transport.  With it, a client can call methods withparameters on a remote server (the server is named by a URI) and get backstructured data.  This module supports writing XML-RPC client code; ithandles all the details of translating between conformable Pythonobjects and XML on the wire. \begin{classdesc}{ServerProxy}{uri\optional{, transport\optional{,                               encoding\optional{, verbose\optional{,                                allow_none\optional{, use_datetime}}}}}}A \class{ServerProxy} instance is an object that manages communicationwith a remote XML-RPC server.  The required first argument is a URI(Uniform Resource Indicator), and will normally be the URL of theserver.  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.  Theoptional third argument is an encoding, by default UTF-8. The optionalfourth argument is a debugging flag.  If \var{allow_none} is true, the Python constant \code{None} will be translated into XML; thedefault behaviour is for \code{None} to raise a \exception{TypeError}.This is a commonly-used extension to the XML-RPC specification, but isn'tsupported by all clients and servers; see\url{http://ontosys.com/xml-rpc/extensions.php} for a description. The \var{use_datetime} flag can be used to cause date/time values to bepresented as \class{\refmodule{datetime}.datetime} objects; this is falseby default.  \class{\refmodule{datetime}.datetime},\class{\refmodule{datetime}.date} and \class{\refmodule{datetime}.time}objects may be passed to calls.  \class{\refmodule{datetime}.date} objectsare converted with a time of ``00:00:00''.\class{\refmodule{datetime}.time} objects are converted using today's date. Both the HTTP and HTTPS transports support the URL syntax extension forHTTP Basic Authentication: \code{http://user:pass@host:port/path}.  The \code{user:pass} portion will be base64-encoded as an HTTP `Authorization'header, and sent to the remote server as part of the connection processwhen invoking an XML-RPC method.  You only need to use this if theremote server requires a Basic Authentication user and password. The returned instance is a proxy object with methods that can be usedto invoke corresponding RPC calls on the remote server.  If the remoteserver supports the introspection API, the proxy can also be used to querythe remote server for the methods it supports (service discovery) andfetch 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 areconformable (e.g. that can be marshalled through XML), include thefollowing (and except where noted, they are unmarshalled as the samePython type): \begin{tableii}{l|l}{constant}{Name}{Meaning}  \lineii{boolean}{The \constant{True} and \constant{False} constants}  \lineii{integers}{Pass in directly}  \lineii{floating-point numbers}{Pass in directly}  \lineii{strings}{Pass in directly}  \lineii{arrays}{Any Python sequence type containing conformable                  elements. Arrays are returned as lists}  \lineii{structures}{A Python dictionary. Keys must be strings,                      values may be any conformable type.}  \lineii{dates}{in seconds since the epoch (pass in an instance of the                 \class{DateTime} class) or a                 \class{\refmodule{datetime}.datetime},                 \class{\refmodule{datetime}.date} or                 \class{\refmodule{datetime}.time} instance}   \lineii{binary data}{pass in an instance of the \class{Binary}                       wrapper class}\end{tableii} This is the full set of data types supported by XML-RPC.  Method callsmay also raise a special \exception{Fault} instance, used to signalXML-RPC server errors, or \exception{ProtocolError} used to signal anerror in the HTTP/HTTPS transport layer.  Both \exception{Fault} and\exception{ProtocolError} derive from a base class called\exception{Error}.  Note that even though starting with Python 2.2 youcan subclass builtin types, the xmlrpclib module currently does notmarshal instances of such subclasses. When passing strings, characters special to XML such as \samp{<},\samp{>}, and \samp{\&} will be automatically escaped.  However, it'sthe caller's responsibility to ensure that the string is free ofcharacters that aren't allowed in XML, such as the control characterswith ASCII values between 0 and 31; failing to do this will result inan XML-RPC request that isn't well-formed XML.  If you have to passarbitrary strings via XML-RPC, use the \class{Binary} wrapper classdescribed below. \class{Server} is retained as an alias for \class{ServerProxy} for backwardscompatibility.  New code should use \class{ServerProxy}. \versionchanged[The \var{use_datetime} flag was added]{2.5}\end{classdesc}  \begin{seealso}  \seetitle[http://www.tldp.org/HOWTO/XML-RPC-HOWTO/index.html]           {XML-RPC HOWTO}{A good description of XML operation and            client software in several languages.  Contains pretty much            everything an XML-RPC client developer needs to know.}  \seetitle[http://xmlrpc-c.sourceforge.net/hacks.php]           {XML-RPC Hacks page}{Extensions for various open-source            libraries to support introspection and multicall.}\end{seealso}  \subsection{ServerProxy Objects \label{serverproxy-objects}} A \class{ServerProxy} instance has a method corresponding toeach remote procedure call accepted by the XML-RPC server.  Callingthe method performs an RPC, dispatched by both name and argumentsignature (e.g. the same method name can be overloaded with multipleargument signatures).  The RPC finishes by returning a value, whichmay 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 commonmethods grouped under the reserved \member{system} member: \begin{methoddesc}{system.listMethods}{}This method returns a list of strings, one for each (non-system)method supported by the XML-RPC server.\end{methoddesc} \begin{methoddesc}{system.methodSignature}{name}This method takes one parameter, the name of a method implemented bythe XML-RPC server.It returns an array of possible signatures for thismethod. A signature is an array of types. The first of these types isthe return type of the method, the rest are parameters. Because multiple signatures (ie. overloading) is permitted, this methodreturns a list of signatures rather than a singleton. Signatures themselves are restricted to the top level parametersexpected by a method. For instance if a method expects one array ofstructs as a parameter, and it returns a string, its signature issimply "string, array". If it expects three integers and returns astring, its signature is "string, int, int, int". If no signature is defined for the method, a non-array value isreturned. In Python this means that the type of the returned value will be something other that list.\end{methoddesc} \begin{methoddesc}{system.methodHelp}{name}This method takes one parameter, the name of a method implemented bythe XML-RPC server.  It returns a documentation string describing theuse of that method. If no such string is available, an empty string isreturned. The documentation string may contain HTML markup.  \end{methoddesc} Introspection methods are currently supported by servers written inPHP, C and Microsoft .NET. Partial introspection support is includedin recent updates to UserLand Frontier. Introspection support forPerl, Python and Java is available at the \ulink{XML-RPCHacks}{http://xmlrpc-c.sourceforge.net/hacks.php} page.  \subsection{Boolean Objects \label{boolean-objects}} This class may be initialized from any Python value; the instancereturned depends only on its truth value.  It supports various Pythonoperators through \method{__cmp__()}, \method{__repr__()},\method{__int__()}, and \method{__nonzero__()} methods, allimplemented in the obvious ways. It also has the following method, supported mainly for internal use bythe unmarshalling code: \begin{methoddesc}{encode}{out}Write the XML-RPC encoding of this Boolean item to the out stream object.\end{methoddesc}  \subsection{DateTime Objects \label{datetime-objects}} This class may be initialized with seconds since the epoch, a time tuple, anISO 8601 time/date string, or a {}\class{\refmodule{datetime}.datetime},{}\class{\refmodule{datetime}.date} or {}\class{\refmodule{datetime}.time}instance.  It has the following methods, supported mainly for internal useby the marshalling/unmarshalling code: \begin{methoddesc}{decode}{string}Accept a string as the instance's new time value.\end{methoddesc} \begin{methoddesc}{encode}{out}Write the XML-RPC encoding of this \class{DateTime} item to the\var{out} stream object.\end{methoddesc} It also supports certain of Python's built-in operators through \method{__cmp__()} and \method{__repr__()} methods.  \subsection{Binary Objects \label{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 isprovided by an attribute: \begin{memberdesc}[Binary]{data}The binary data encapsulated by the \class{Binary} instance.  The datais provided as an 8-bit string.\end{memberdesc} \class{Binary} objects have the following methods, supported mainlyfor internal use by the marshalling/unmarshalling code: \begin{methoddesc}[Binary]{decode}{string}Accept a base64 string and decode it as the instance's new data.\end{methoddesc} \begin{methoddesc}[Binary]{encode}{out}Write the XML-RPC base 64 encoding of this binary item to the outstream object.\end{methoddesc} It also supports certain of Python's built-in operators through a\method{__cmp__()} method.  \subsection{Fault Objects \label{fault-objects}} A \class{Fault} object encapsulates the content of an XML-RPC fault tag.Fault objects have the following members: \begin{memberdesc}{faultCode}A string indicating the fault type.\end{memberdesc} \begin{memberdesc}{faultString}A string containing a diagnostic message associated with the fault.\end{memberdesc}  \subsection{ProtocolError Objects \label{protocol-error-objects}} A \class{ProtocolError} object describes a protocol error in theunderlying transport layer (such as a 404 `not found' error if theserver named by the URI does not exist).  It has the followingmembers: \begin{memberdesc}{url}The URI or URL that triggered the error.\end{memberdesc} \begin{memberdesc}{errcode}The error code.\end{memberdesc} \begin{memberdesc}{errmsg}The error message or diagnostic string.\end{memberdesc} \begin{memberdesc}{headers}A string containing the headers of the HTTP/HTTPS request thattriggered the error.\end{memberdesc} \subsection{MultiCall Objects} \versionadded{2.4} In \url{http://www.xmlrpc.com/discuss/msgReader\%241208}, an approachis presented to encapsulate multiple calls to a remote server into asingle request. \begin{classdesc}{MultiCall}{server} Create an object used to boxcar method calls. \var{server} is theeventual target of the call. Calls can be made to the result object,but they will immediately return \var{None}, and only store thecall name and parameters in the \class{MultiCall} object. Callingthe object itself causes all stored calls to be transmitted asa single \code{system.multicall} request. The result of this callis a generator; iterating over this generator yields the individualresults. \end{classdesc} A usage example of this class is \begin{verbatim}multicall = MultiCall(server_proxy)multicall.add(2,3)multicall.get_address("Guido")add_result, address = multicall()\end{verbatim} \subsection{Convenience Functions} \begin{funcdesc}{boolean}{value}Convert any Python value to one of the XML-RPC Boolean constants,\code{True} or \code{False}.\end{funcdesc} \begin{funcdesc}{dumps}{params\optional{, methodname\optional{, 	                methodresponse\optional{, encoding\optional{,	                allow_none}}}}}Convert \var{params} into an XML-RPC request.or into a response if \var{methodresponse} is true.\var{params} can be either a tuple of arguments or an instance of the \exception{Fault} exception class.  If \var{methodresponse} is true,only a single value can be returned, meaning that \var{params} must be of length 1.\var{encoding}, if supplied, is the encoding to use in the generatedXML; the default is UTF-8.  Python's \constant{None} value cannot beused in standard XML-RPC; to allow using it via an extension, provide a true value for \var{allow_none}.\end{funcdesc} \begin{funcdesc}{loads}{data\optional{, use_datetime}}Convert an XML-RPC request or response into Python objects, a\code{(\var{params}, \var{methodname})}.  \var{params} is a tuple of argument; \var{methodname}is a string, or \code{None} if no method name is present in the packet.If the XML-RPC packet represents a fault condition, thisfunction will raise a \exception{Fault} exception.The \var{use_datetime} flag can be used to cause date/time values to bepresented as \class{\refmodule{datetime}.datetime} objects; this is falseby default.Note that even if you call an XML-RPC method with\class{\refmodule{datetime}.date} or \class{\refmodule{datetime}.time}objects, they are converted to \class{DateTime} objects internally, so only{}\class{\refmodule{datetime}.datetime} objects will be returned. \versionchanged[The \var{use_datetime} flag was added]{2.5}\end{funcdesc}   \subsection{Example of Client Usage \label{xmlrpc-client-example}} \begin{verbatim}# simple test program (from the XML-RPC specification)from xmlrpclib import ServerProxy, Error # server = ServerProxy("http://localhost:8000") # local serverserver = ServerProxy("http://betty.userland.com") print server try:    print server.examples.getStateName(41)except Error, v:    print "ERROR", v\end{verbatim} To access an XML-RPC server through a proxy, you need to define a custom transport.  The following example, written by NoboNobo, % fill in original author's name if we ever learn itshows how: % Example taken from http://lowlife.jp/nobonobo/wiki/xmlrpcwithproxy.html\begin{verbatim}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()\end{verbatim}