title: Pandas: Check if column exists in df from a list of columns
body: <p>Goal here is to find the columns that does not exist in df and create them with null values.</p>
  
  <p>I have a list of column names like below:</p>
  
  <pre><code>column_list = ('column_1', 'column_2', 'column_3')
  </code></pre>
  
  <p>When I try to check if the column exists, it gives out True for only columns that exist and do not get False for those that are missing.</p>
  
  <pre><code>for column in column_list:
      print df.columns.isin(column_list).any()
  </code></pre>
  
  <p>In PySpark, I can achieve this using the below:</p>
  
  <pre><code>for column in column_list:
          if not column in df.columns:
              df = df.withColumn(column, lit(''))
  </code></pre>
  
  <p>How can I achieve the same using Pandas?</p>