title: How to copy the column headers of a data frame to each row value?
body: <p>I'm trying to transform a pandas data frame, applying a function to all values, to concatenate the column header and the actual value.</p>
  
  <p>My original dataframe is something like this:</p>
  
  <pre><code>|---------------------|------------------|
  |         Col1        |        Col2      |
  |---------------------|------------------|
  |          12         |         34       |
  |---------------------|------------------|
  |          12         |         34       |
  </code></pre>
  
  <p>The output should be:</p>
  
  <pre><code>|---------------------|------------------|
  |       Col1          |      Col2        |
  |---------------------|------------------|
  |       Col1_12       |      Col2_34     |
  |---------------------|------------------|
  |       Col1_12       |      Col2_34     |
  </code></pre>
  
  <p>What I tried is this:</p>
  
  <pre><code>mypandasdf.applymap(lambda x: 'columnname'+'_'+str(x))
  </code></pre>
  
  <p>But I'm struggling with the column name value. How can I put the real column name instead of a string?
  Or is there any other/better way to do it?</p>