title: how to convert a float/integer into a date with strptime?
body: <p>I have a pandas dataframe that contains the following columns:</p>
  
  <pre><code>col1 col2
  20040929 NaN
  NaN 20040925 
  </code></pre>
  
  <p>that is both both col1 and col2 are float64 (or int64) numbers.
  I am trying to convert these using datetime.strptime() but I get the error</p>
  
  <blockquote>
    <p>"cannot convert the series to type 'float'"</p>
  </blockquote>
  
  <p>and if I convert them to float, I get something like 20040929.0 which strptime does not understand.</p>
  
  <p>How can I transform these columns into date then?
  Many thanks</p>