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<h1 class="title">Python Programming Guide</h1>
<p>The Spark Python API (PySpark) exposes the Spark programming model to Python.
To learn the basics of Spark, we recommend reading through the
<a href="scala-programming-guide.html">Scala programming guide</a> first; it should be
easy to follow even if you don’t know Scala.
This guide will show how to use the Spark features described there in Python.</p>
<h1 id="key-differences-in-the-python-api">Key Differences in the Python API</h1>
<p>There are a few key differences between the Python and Scala APIs:</p>
<ul>
<li>Python is dynamically typed, so RDDs can hold objects of multiple types.</li>
<li>PySpark does not yet support a few API calls, such as <code>lookup</code> and non-text input files, though these will be added in future releases.</li>
</ul>
<p>In PySpark, RDDs support the same methods as their Scala counterparts but take Python functions and return Python collection types.
Short functions can be passed to RDD methods using Python’s <a href="http://www.diveintopython.net/power_of_introspection/lambda_functions.html"><code>lambda</code></a> syntax:</p>
<div class="highlight"><pre><code class="python"><span class="n">logData</span> <span class="o">=</span> <span class="n">sc</span><span class="o">.</span><span class="n">textFile</span><span class="p">(</span><span class="n">logFile</span><span class="p">)</span><span class="o">.</span><span class="n">cache</span><span class="p">()</span>
<span class="n">errors</span> <span class="o">=</span> <span class="n">logData</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="k">lambda</span> <span class="n">line</span><span class="p">:</span> <span class="s">"ERROR"</span> <span class="ow">in</span> <span class="n">line</span><span class="p">)</span>
</code></pre></div>
<p>You can also pass functions that are defined with the <code>def</code> keyword; this is useful for longer functions that can’t be expressed using <code>lambda</code>:</p>
<div class="highlight"><pre><code class="python"><span class="k">def</span> <span class="nf">is_error</span><span class="p">(</span><span class="n">line</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"ERROR"</span> <span class="ow">in</span> <span class="n">line</span>
<span class="n">errors</span> <span class="o">=</span> <span class="n">logData</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">is_error</span><span class="p">)</span>
</code></pre></div>
<p>Functions can access objects in enclosing scopes, although modifications to those objects within RDD methods will not be propagated back:</p>
<div class="highlight"><pre><code class="python"><span class="n">error_keywords</span> <span class="o">=</span> <span class="p">[</span><span class="s">"Exception"</span><span class="p">,</span> <span class="s">"Error"</span><span class="p">]</span>
<span class="k">def</span> <span class="nf">is_error</span><span class="p">(</span><span class="n">line</span><span class="p">):</span>
<span class="k">return</span> <span class="nb">any</span><span class="p">(</span><span class="n">keyword</span> <span class="ow">in</span> <span class="n">line</span> <span class="k">for</span> <span class="n">keyword</span> <span class="ow">in</span> <span class="n">error_keywords</span><span class="p">)</span>
<span class="n">errors</span> <span class="o">=</span> <span class="n">logData</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">is_error</span><span class="p">)</span>
</code></pre></div>
<p>PySpark will automatically ship these functions to workers, along with any objects that they reference.
Instances of classes will be serialized and shipped to workers by PySpark, but classes themselves cannot be automatically distributed to workers.
The <a href="#standalone-use">Standalone Use</a> section describes how to ship code dependencies to workers.</p>
<p>In addition, PySpark fully supports interactive use—simply run <code>./bin/pyspark</code> to launch an interactive shell.</p>
<h1 id="installing-and-configuring-pyspark">Installing and Configuring PySpark</h1>
<p>PySpark requires Python 2.6 or higher.
PySpark applications are executed using a standard CPython interpreter in order to support Python modules that use C extensions.
We have not tested PySpark with Python 3 or with alternative Python interpreters, such as <a href="http://pypy.org/">PyPy</a> or <a href="http://www.jython.org/">Jython</a>.</p>
<p>By default, PySpark requires <code>python</code> to be available on the system <code>PATH</code> and use it to run programs; an alternate Python executable may be specified by setting the <code>PYSPARK_PYTHON</code> environment variable in <code>conf/spark-env.sh</code> (or <code>.cmd</code> on Windows).</p>
<p>All of PySpark’s library dependencies, including <a href="http://py4j.sourceforge.net/">Py4J</a>, are bundled with PySpark and automatically imported.</p>
<p>Standalone PySpark applications should be run using the <code>bin/pyspark</code> script, which automatically configures the Java and Python environment using the settings in <code>conf/spark-env.sh</code> or <code>.cmd</code>.
The script automatically adds the <code>bin/pyspark</code> package to the <code>PYTHONPATH</code>.</p>
<h1 id="interactive-use">Interactive Use</h1>
<p>The <code>bin/pyspark</code> script launches a Python interpreter that is configured to run PySpark applications. To use <code>pyspark</code> interactively, first build Spark, then launch it directly from the command line without any options:</p>
<div class="highlight"><pre><code class="bash"><span class="nv">$ </span>sbt/sbt assembly
<span class="nv">$ </span>./bin/pyspark
</code></pre></div>
<p>The Python shell can be used explore data interactively and is a simple way to learn the API:</p>
<div class="highlight"><pre><code class="python"><span class="o">>>></span> <span class="n">words</span> <span class="o">=</span> <span class="n">sc</span><span class="o">.</span><span class="n">textFile</span><span class="p">(</span><span class="s">"/usr/share/dict/words"</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">words</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="k">lambda</span> <span class="n">w</span><span class="p">:</span> <span class="n">w</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s">"spar"</span><span class="p">))</span><span class="o">.</span><span class="n">take</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="p">[</span><span class="s">u'spar'</span><span class="p">,</span> <span class="s">u'sparable'</span><span class="p">,</span> <span class="s">u'sparada'</span><span class="p">,</span> <span class="s">u'sparadrap'</span><span class="p">,</span> <span class="s">u'sparagrass'</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">help</span><span class="p">(</span><span class="n">pyspark</span><span class="p">)</span> <span class="c"># Show all pyspark functions</span>
</code></pre></div>
<p>By default, the <code>bin/pyspark</code> shell creates SparkContext that runs applications locally on a single core.
To connect to a non-local cluster, or use multiple cores, set the <code>MASTER</code> environment variable.
For example, to use the <code>bin/pyspark</code> shell with a <a href="spark-standalone.html">standalone Spark cluster</a>:</p>
<div class="highlight"><pre><code class="bash"><span class="nv">$ MASTER</span><span class="o">=</span>spark://IP:PORT ./bin/pyspark
</code></pre></div>
<p>Or, to use four cores on the local machine:</p>
<div class="highlight"><pre><code class="bash"><span class="nv">$ MASTER</span><span class="o">=</span><span class="nb">local</span><span class="o">[</span>4<span class="o">]</span> ./bin/pyspark
</code></pre></div>
<h2 id="ipython">IPython</h2>
<p>It is also possible to launch PySpark in <a href="http://ipython.org">IPython</a>, the
enhanced Python interpreter. PySpark works with IPython 1.0.0 and later. To
use IPython, set the <code>IPYTHON</code> variable to <code>1</code> when running <code>bin/pyspark</code>:</p>
<div class="highlight"><pre><code class="bash"><span class="nv">$ IPYTHON</span><span class="o">=</span>1 ./bin/pyspark
</code></pre></div>
<p>Alternatively, you can customize the <code>ipython</code> command by setting <code>IPYTHON_OPTS</code>. For example, to launch
the <a href="http://ipython.org/notebook.html">IPython Notebook</a> with PyLab graphing support:</p>
<div class="highlight"><pre><code class="bash"><span class="nv">$ IPYTHON_OPTS</span><span class="o">=</span><span class="s2">"notebook --pylab inline"</span> ./bin/pyspark
</code></pre></div>
<p>IPython also works on a cluster or on multiple cores if you set the <code>MASTER</code> environment variable.</p>
<h1 id="standalone-programs">Standalone Programs</h1>
<p>PySpark can also be used from standalone Python scripts by creating a SparkContext in your script and running the script using <code>bin/pyspark</code>.
The Quick Start guide includes a <a href="quick-start.html#a-standalone-app-in-python">complete example</a> of a standalone Python application.</p>
<p>Code dependencies can be deployed by listing them in the <code>pyFiles</code> option in the SparkContext constructor:</p>
<div class="highlight"><pre><code class="python"><span class="kn">from</span> <span class="nn">pyspark</span> <span class="kn">import</span> <span class="n">SparkContext</span>
<span class="n">sc</span> <span class="o">=</span> <span class="n">SparkContext</span><span class="p">(</span><span class="s">"local"</span><span class="p">,</span> <span class="s">"App Name"</span><span class="p">,</span> <span class="n">pyFiles</span><span class="o">=</span><span class="p">[</span><span class="s">'MyFile.py'</span><span class="p">,</span> <span class="s">'lib.zip'</span><span class="p">,</span> <span class="s">'app.egg'</span><span class="p">])</span>
</code></pre></div>
<p>Files listed here will be added to the <code>PYTHONPATH</code> and shipped to remote worker machines.
Code dependencies can be added to an existing SparkContext using its <code>addPyFile()</code> method.</p>
<p>You can set <a href="configuration.html#spark-properties">configuration properties</a> by passing a
<a href="api/pyspark/pyspark.conf.SparkConf-class.html">SparkConf</a> object to SparkContext:</p>
<div class="highlight"><pre><code class="python"><span class="kn">from</span> <span class="nn">pyspark</span> <span class="kn">import</span> <span class="n">SparkConf</span><span class="p">,</span> <span class="n">SparkContext</span>
<span class="n">conf</span> <span class="o">=</span> <span class="p">(</span><span class="n">SparkConf</span><span class="p">()</span>
<span class="o">.</span><span class="n">setMaster</span><span class="p">(</span><span class="s">"local"</span><span class="p">)</span>
<span class="o">.</span><span class="n">setAppName</span><span class="p">(</span><span class="s">"My app"</span><span class="p">)</span>
<span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s">"spark.executor.memory"</span><span class="p">,</span> <span class="s">"1g"</span><span class="p">))</span>
<span class="n">sc</span> <span class="o">=</span> <span class="n">SparkContext</span><span class="p">(</span><span class="n">conf</span> <span class="o">=</span> <span class="n">conf</span><span class="p">)</span>
</code></pre></div>
<h1 id="api-docs">API Docs</h1>
<p><a href="api/pyspark/index.html">API documentation</a> for PySpark is available as Epydoc.
Many of the methods also contain <a href="http://docs.python.org/2/library/doctest.html">doctests</a> that provide additional usage examples.</p>
<h1 id="libraries">Libraries</h1>
<p><a href="mllib-guide.html">MLlib</a> is also available in PySpark. To use it, you’ll need
<a href="http://www.numpy.org">NumPy</a> version 1.7 or newer, and Python 2.7. The <a href="mllib-guide.html">MLlib guide</a> contains
some example applications.</p>
<h1 id="where-to-go-from-here">Where to Go from Here</h1>
<p>PySpark also includes several sample programs in the <a href="https://github.com/apache/incubator-spark/tree/master/python/examples"><code>python/examples</code> folder</a>.
You can run them by passing the files to <code>pyspark</code>; e.g.:</p>
<pre><code>./bin/pyspark python/examples/wordcount.py
</code></pre>
<p>Each program prints usage help when run without arguments.</p>
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$(function() {
function maybeScrollToHash() {
if (window.location.hash && $(window.location.hash).length) {
var newTop = $(window.location.hash).offset().top - $('#topbar').height() - 5;
$(window).scrollTop(newTop);
}
}
$(window).bind('hashchange', function() {
maybeScrollToHash();
});
// Scroll now too in case we had opened the page on a hash, but wait 1 ms because some browsers
// will try to do *their* initial scroll after running the onReady handler.
setTimeout(function() { maybeScrollToHash(); }, 1)
})
</script>
</body>
</html>
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