title: ValueError: Cannot run multiple SparkContexts at once in spark with pyspark
body: <p>i am new in using spark , i try to run this code on pyspark </p>
  
  <pre><code>from pyspark import SparkConf, SparkContext
  import collections
  
  conf = SparkConf().setMaster("local").setAppName("RatingsHistogram")
  sc = SparkContext(conf = conf)
  </code></pre>
  
  <p>but he till me this erore message </p>
  
  <pre><code>Using Python version 3.5.2 (default, Jul  5 2016 11:41:13)
  SparkSession available as 'spark'.
  &gt;&gt;&gt; from pyspark import SparkConf, SparkContext
  &gt;&gt;&gt; import collections
  &gt;&gt;&gt; conf = SparkConf().setMaster("local").setAppName("RatingsHistogram")
  &gt;&gt;&gt; sc = SparkContext(conf = conf)
  
  
  
     Traceback (most recent call last):
        File "&lt;stdin&gt;", line 1, in &lt;module&gt;
        File "C:\spark\python\pyspark\context.py", line 115, in __init__
          SparkContext._ensure_initialized(self, gateway=gateway, conf=conf)
        File "C:\spark\python\pyspark\context.py", line 275, in _ensure_initialized
          callsite.function, callsite.file, callsite.linenum))
      ValueError: Cannot run multiple SparkContexts at once; existing SparkContext(app=PySparkShell, master=local[*]) created by getOrCreate at C:\spark\bin\..\python\pyspark\shell.py:43
      &gt;&gt;&gt;
  </code></pre>
  
  <p>i have version spark 2.1.1 and python 3.5.2 , i search and found it is problem in sc ,he could not read it but no when till why , any one have help here </p>