title: I'm trying to find the last column with data in each row and return the column name to the data frame
body: <p>I'm trying to get the column name the value from ffill is from.</p>
  
  <p>I've searched google and stack overflow and haven't found a way to accomplish this.</p>
  
  <p>This is the ffill code:
      df["LAST_PUNCH"] = df.ffill(axis=1).iloc[:, -1]</p>
  
  <p>This is my dataframe:</p>
  
  <pre><code>SHIFT     IN     OUT    IN_1    
  DA6-0730  07:30  12:35  13:05      
  DB0-ACOM  08:18  12:30             
  DC4-0730  07:30  12:39  13:09     
  DC4-0730  07:30  12:34  13:04     
  </code></pre>
  
  <p>This is my dataframe after using ffill:</p>
  
  <pre><code>SHIFT     IN     OUT    IN_1   LAST_PUNCH
  DA6-0730  07:30  12:35  13:05  13:05
  DB0-ACOM  08:18  12:30         12:30
  DC4-0730  07:30  12:39  13:09  13:09
  DC4-0730  07:30  12:34  13:04  13:04
  </code></pre>
  
  <p>I would like to get the column name where the ffill value came from and 
  append to the end of the ffill value:</p>
  
  <pre><code>SHIFT     IN     OUT    IN_1   LAST_PUNCH
  DA6-0730  07:30  12:35  13:05  13:05_IN_1
  DB0-ACOM  08:18  12:30         12:30_OUT
  DC4-0730  07:30  12:39  13:09  13:09_IN_1
  DC4-0730  07:30  12:34  13:04  13:04_IN_1
  </code></pre>