title: Merging multiple panda frames
body: <p>I have a bunch of CSV files which contain data for a specific time and time is encoded as the filename:</p>
  <pre><code>time1.csv
  Label val1 val2
  a      5    6
  b.     6    4
  
  time2.csv
  Label val1 val2
  a      5    6
  c      6    4
  
  ...
  </code></pre>
  <p>I can read each file into a Pandas data frame. Then I want to:
  Add the &quot;time&quot; column into each data frame and then merge all the data frames into a single data frame.</p>
  <p>Is there a way to accomplish this?</p>