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<h1 id="python-3">Python 3</h1>
<p>In this example, we’re going to send a pair of coordinates to the <a href="http://navigator.state.or.us/arcgis/rest/services/Framework/Admin_Bounds_WM/MapServer/4" target="_blank">House Districts service</a> to determine what house district the location is located in. We can also get the name of the elected representative associated with that district.</p>
<h2 id="example">Example</h2>
<p><strong>Prerequisites</strong>:</p>
<ul>
<li><a href="https://www.python.org/downloads/" target="_blank">Python 3</a></li>
<li><a href="https://pypi.org/project/pip/" target="_blank">pip</a> (included by default starting at Python 3.4)</li>
</ul>
<p>Install the <a href="http://docs.python-requests.org/en/master/" target="_blank">Requests package</a> with <a href="https://docs.python.org/3/installing/index.html" target="_blank">pip</a>. <a href="http://docs.python-requests.org/en/master/" target="_blank">Requests</a> is an HTTP library that we will use to make requests to our GIS services. You could also use something like the <a href="https://docs.python.org/3/library/urllib.html">urllib package</a>.</p>
<p>In you command prompt, install the package with:</p>
<div class="language-bash highlighter-rouge"><div class="highlight"><pre class="highlight"><code>pip <span class="nb">install </span>requests
</code></pre></div></div>
<p>Next, create a file and name it <code class="highlighter-rouge">get_house_district.py</code> and paste the following:</p>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kn">import</span> <span class="nn">requests</span><span class="p">,</span> <span class="n">json</span>
<span class="n">input_coordinates</span> <span class="o">=</span> <span class="p">{</span>
<span class="s">'lat'</span><span class="p">:</span> <span class="mf">44.921019</span><span class="p">,</span>
<span class="s">'lng'</span><span class="p">:</span> <span class="o">-</span><span class="mf">123.315793</span>
<span class="p">}</span>
<span class="n">house_districts_service_url</span> <span class="o">=</span> <span class="s">'https://navigator.state.or.us/arcgis/rest/services/Framework/Admin_Bounds_WM/MapServer/4/query'</span>
<span class="n">payload</span> <span class="o">=</span> <span class="p">{</span>
<span class="s">'inSR'</span><span class="p">:</span> <span class="mi">4326</span><span class="p">,</span>
<span class="s">'geometry'</span><span class="p">:</span> <span class="s">'{lng},{lat}'</span><span class="o">.</span><span class="nb">format</span><span class="p">(</span><span class="n">lng</span><span class="o">=</span><span class="n">input_coordinates</span><span class="p">[</span><span class="s">'lng'</span><span class="p">],</span><span class="n">lat</span><span class="o">=</span><span class="n">input_coordinates</span><span class="p">[</span><span class="s">'lat'</span><span class="p">]),</span>
<span class="s">'geometryType'</span><span class="p">:</span> <span class="s">'esriGeometryPoint'</span><span class="p">,</span>
<span class="s">'spatialRel'</span><span class="p">:</span> <span class="s">'esriSpatialRelIntersects'</span><span class="p">,</span>
<span class="s">'outSR'</span><span class="p">:</span> <span class="mi">4326</span><span class="p">,</span>
<span class="s">'outFields'</span><span class="p">:</span> <span class="s">'*'</span><span class="p">,</span>
<span class="s">'returnGeometry'</span><span class="p">:</span> <span class="s">'false'</span><span class="p">,</span>
<span class="s">'f'</span><span class="p">:</span> <span class="s">'json'</span>
<span class="p">}</span>
<span class="n">r</span> <span class="o">=</span> <span class="n">requests</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">house_districts_service_url</span><span class="p">,</span> <span class="n">params</span><span class="o">=</span><span class="n">payload</span><span class="p">)</span>
<span class="n">match</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">text</span><span class="p">)[</span><span class="s">'features'</span><span class="p">][</span><span class="mi">0</span><span class="p">][</span><span class="s">'attributes'</span><span class="p">]</span>
<span class="k">print</span><span class="p">(</span><span class="s">'Matched District:'</span><span class="p">,</span> <span class="n">match</span><span class="p">[</span><span class="s">'DISTRICT'</span><span class="p">])</span> <span class="c1"># 23
</span><span class="k">print</span><span class="p">(</span><span class="s">"District Party"</span><span class="p">,</span> <span class="n">match</span><span class="p">[</span><span class="s">'Party'</span><span class="p">])</span> <span class="c1"># Republican
</span><span class="k">print</span><span class="p">(</span><span class="s">"Representative:"</span><span class="p">,</span> <span class="n">match</span><span class="p">[</span><span class="s">'Name'</span><span class="p">])</span> <span class="c1"># Mike Nearman
</span></code></pre></div></div>
<p>This python code accomplished the following:</p>
<ol>
<li>Defines <code class="highlighter-rouge">input_coordinates</code>. This is the location we want to use to determine the intersecting house district.</li>
<li>Defines the URL (<code class="highlighter-rouge">house_districts_service_url</code>) and parameters (<code class="highlighter-rouge">payload</code>) we want to build our query (more on this below).</li>
<li>Sends the request to the GIS service using the Requests library.</li>
<li>Parses the request and prints the matched output.</li>
</ol>
<p>Probably the most difficult part of this process is understanding what parameters we need to pass to the request. The <a href="http://navigator.state.or.us/arcgis/sdk/rest/index.html#//02ss0000000r000000" target="_blank">ArcGIS REST API</a> documents what parameters you can use in the request, but this might not be helpful to developers not familiar with geospatial concepts. Here is a quick guide to understanding our inputs:</p>
<ul>
<li>
<p><strong>inSR</strong> - The input spatial reference or our coordinates. In this case, we are providing geographic coordinates in degrees using <a href="https://epsg.io/4326" target="_blank">EPSG:4326</a>.</p>
</li>
<li>
<p><strong>geometry</strong> - The input coordinates for our point.</p>
</li>
<li>
<p><strong>geometryType</strong> - The geometry type, in our case a point.</p>
</li>
<li>
<p><strong>spatialRel</strong> - The spatial relationship. In our case, we are looking for the house district that <code class="highlighter-rouge">intersects</code> with our point.</p>
</li>
<li>
<p><strong>outSR</strong> - The spatial reference we want our result to be in.</p>
</li>
<li>
<p><strong>ourFields</strong> - The fields we want returned. In our case, we want all fields (<code class="highlighter-rouge">*</code>).</p>
</li>
<li>
<p><strong>returnGeometry</strong> - Whether or not we want the actual geometry of the intersecting house district.</p>
</li>
<li>
<p><strong>f</strong> - The type of response we want returned.</p>
</li>
</ul>
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