title: Why can't PySpark find py4j.java_gateway?
body: <p>I installed Spark, ran the sbt assembly, and can open bin/pyspark with no problem. However, I am running into problems loading the pyspark module into ipython. I'm getting the following error:</p>
  
  <pre><code>In [1]: import pyspark
  ---------------------------------------------------------------------------
  ImportError                               Traceback (most recent call last)
  &lt;ipython-input-1-c15ae3402d12&gt; in &lt;module&gt;()
  ----&gt; 1 import pyspark
  
  /usr/local/spark/python/pyspark/__init__.py in &lt;module&gt;()
       61
       62 from pyspark.conf import SparkConf
  ---&gt; 63 from pyspark.context import SparkContext
       64 from pyspark.sql import SQLContext
       65 from pyspark.rdd import RDD
  
  /usr/local/spark/python/pyspark/context.py in &lt;module&gt;()
       28 from pyspark.conf import SparkConf
       29 from pyspark.files import SparkFiles
  ---&gt; 30 from pyspark.java_gateway import launch_gateway
       31 from pyspark.serializers import PickleSerializer, BatchedSerializer, UTF8Deserializer, \
       32     PairDeserializer, CompressedSerializer
  
  /usr/local/spark/python/pyspark/java_gateway.py in &lt;module&gt;()
       24 from subprocess import Popen, PIPE
       25 from threading import Thread
  ---&gt; 26 from py4j.java_gateway import java_import, JavaGateway, GatewayClient
       27
       28
  
  ImportError: No module named py4j.java_gateway
  </code></pre>