title: pyspark drop duplicate column
body: <p>I am using pyspark 2.4.0, I have an dataframe with below columns</p>
  <pre><code>a,b,b
  0,1,1.0
  1,2,2.0
  </code></pre>
  <p>Without any join I have to keep only either one of b column and remove other b column</p>
  <p>How can I achieve this</p>