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<h2 class="title"><a name="soap.firststeps"></a>12.3. First Steps with <span class="acronym">SOAP</span></h2>
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<div class="abstract">
<p>The heart of <span class="acronym">SOAP</span> is the ability to call remote functions. There are a number of public access <span class="acronym">SOAP</span> servers that provide simple functions for demonstration purposes.
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<p>The most popular public access <span class="acronym">SOAP</span> server is <a href="http://www.xmethods.net/">http://www.xmethods.net/</a>. This example uses a demonstration function that takes a United States zip code and returns the current temperature in that
region.
</p>
<div class="example"><a name="d0e30286"></a><h3 class="title">Example 12.6. Getting the Current Temperature</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput"><span class='pykeyword'>from</span> SOAPpy <span class='pykeyword'>import</span> SOAPProxy</span> <a name="soap.firststeps.1.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">url = <span class='pystring'>'http://services.xmethods.net:80/soap/servlet/rpcrouter'</span></span>
<tt class="prompt">>>> </tt><span class="userinput">namespace = <span class='pystring'>'urn:xmethods-Temperature'</span></span> <a name="soap.firststeps.1.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">server = SOAPProxy(url, namespace)</span> <a name="soap.firststeps.1.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">server.getTemp(<span class='pystring'>'27502'</span>)</span> <a name="soap.firststeps.1.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<span class="computeroutput">80.0</span>
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<td valign="top" align="left">You access the remote <span class="acronym">SOAP</span> server through a proxy class, <tt class="classname">SOAPProxy</tt>. The proxy handles all the internals of <span class="acronym">SOAP</span> for you, including creating the XML request document out of the function name and argument list, sending the request over
HTTP to the remote <span class="acronym">SOAP</span> server, parsing the XML response document, and creating native <span class="application">Python</span> values to return. You'll see what these XML documents look like in the next section.
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<td valign="top" align="left">Every <span class="acronym">SOAP</span> service has a <span class="acronym">URL</span> which handles all the requests. The same <span class="acronym">URL</span> is used for all function calls. This particular service only has a single function, but later in this chapter you'll see
examples of the Google <span class="acronym">API</span>, which has several functions. The service <span class="acronym">URL</span> is shared by all functions.Each <span class="acronym">SOAP</span> service also has a namespace, which is defined by the server and is completely arbitrary. It's simply part of the configuration
required to call <span class="acronym">SOAP</span> methods. It allows the server to share a single service <span class="acronym">URL</span> and route requests between several unrelated services. It's like dividing <span class="application">Python</span> modules into <a href="../xml_processing/packages.html" title="9.2. Packages">packages</a>.
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<td valign="top" align="left">You're creating the <tt class="classname">SOAPProxy</tt> with the service <span class="acronym">URL</span> and the service namespace. This doesn't make any connection to the <span class="acronym">SOAP</span> server; it simply creates a local <span class="application">Python</span> object.
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<td valign="top" align="left">Now with everything configured properly, you can actually call remote <span class="acronym">SOAP</span> methods as if they were local functions. You pass arguments just like a normal function, and you get a return value just
like a normal function. But under the covers, there's a heck of a lot going on.
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<p>Let's peek under those covers.</p>
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