title: Pandas - looping through columns of a dataframe and join this column with other dataframe
body: <p>I have a DataFrame (df1)</p>
  
  <pre><code>index abc bcd def 
  20150101 0.5 0.3 0.2
  20150102 0.7 0.9 1.6
  20150103 1.7 2.9 4.6
  .................
  </code></pre>
  
  <p>second dataframe (df2)</p>
  
  <pre><code>index a b c ...(about 100 columns)
  0 0 1 8 ...
  1 9 5 3 ...
  2 2 3 7 ..
  </code></pre>
  
  <p>I would like to loop through each column in 2nd dataframe and need to form a dataframe in every loop like</p>
  
  <pre><code> index abc bcd def col
   20150101 0.5 0.3 0.2 0
   20150102 0.7 0.9 1.6 9
   20150103 1.7 2.9 4.6 2
  </code></pre>
  
  <p>and need to work on this new dataframe for other calculations</p>
  
  <p>I am running this, </p>
  
  <pre><code>    for col in df2.iteritems():
          df1['new_col'] = col
  </code></pre>
  
  <p>with error: ValueError: Length of values does not match length of index</p>
  
  <p>If I form a series from col as in </p>
  
  <pre><code>    for col in df2.iteritems():
          c = col[1].astype(float)
          s = pd.Series(c)
           dfb['col'] = s
  </code></pre>
  
  <p>gives</p>
  
  <pre><code>index abc bcd def col
  20150101 0.5 0.3 0.2 NaN
  20150102 0.7 0.9 1.6 NaN
  20150103 1.7 2.9 4.6 NaN
  </code></pre>
  
  <p>please suggest a solution. Thanks in Advance!</p>