title: How do I convert a list in a Pandas DF into a string?
body: <p>I have a pandas data frame.  One of the columns contains a list.  I want that column to be a single string.</p>
  <p>For example my list <code>['one','two','three']</code> should simply be <code>'one, two, three'</code></p>
  <pre><code>df['col'] = df['col'].astype(str).apply(lambda x: ', '.join(df['col'].astype(str)))
  </code></pre>
  <p>gives me <code>['one, two, three],['four','five','six']</code>  where the second list is from the next row. Needless to say with millions of rows this concatenation across rows is not only incorrect, it kills my memory.</p>