title: Pivot column and column values in pandas dataframe
body: <p>I have a dataframe that looks like this, but with 26 rows and 110 columns: </p>
  
  <pre><code>index/io   1   2   3   4
    0        42  53  23  4
    1        53  24  6   12
    2        63  12  65  34
    3        13  64  23  43
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>index  io  value
  0      1   42
  0      2   53
  0      3   23
  0      4   4
  1      1   53
  1      2   24
  1      3   6
  1      4   12
  2      1   63
  2      2   12
  ... 
  </code></pre>
  
  <p>I have tried with dict and lists by transforming the dataframe to dict, and then create a new list with index values and update in new dict with io.</p>
  
  <pre><code>indx = []
  
  for key, value in mydict.iteritems():
      for k, v in value.iteritems():
          indx.append(key)
  indxio = {}
  for element in indx:
      for key, value in mydict.iteritems():
          for k, v in value.iteritems():
              indxio.update({element:k})
  </code></pre>
  
  <p>I know this is too far probably, but it's the only thing I could think of. The process was too long, so I stopped.  </p>