title: Selecting columns by list (and columns are subset of list)
body: <p>I'm selecting several columns of a dataframe, by a list of the column names. This works fine if all elements of the list are in the dataframe.
  But if some elements of the list are not in the DataFrame, then it will generate the error &quot;not in index&quot;.</p>
  <p>Is there a way to select all columns which included in that list, even if not all elements of the list are included in the dataframe? Here is some sample data which generates the above error:</p>
  <pre><code>df   = pd.DataFrame( [[0,1,2]], columns=list('ABC') )
  
  lst  = list('ARB')
  
  data = df[lst]       # error: not in index
  </code></pre>