title: How can I iterate through two Pandas columns?
body: <p>Consider:</p>
  <pre class="lang-none prettyprint-override"><code>In [35]: test = pd.DataFrame({'a':range(4),'b':range(4,8)})
  
  In [36]: test
  Out[36]:
     a  b
  0  0  4
  1  1  5
  2  2  6
  3  3  7
  
  In [37]: for i in test['a']:
     ....:  print i
     ....:
  0
  1
  2
  3
  
  In [38]: for i,j in test:
     ....:  print i,j
     ....:
  ------------------------------------------------------------
  Traceback (most recent call last):
    File &quot;&lt;ipython console&gt;&quot;, line 1, in &lt;module&gt;
  ValueError: need more than 1 value to unpack
  
  
  In [39]: for i,j in test[['a','b']]:
     ....:  print i,j
     ....:
  ------------------------------------------------------------
  Traceback (most recent call last):
    File &quot;&lt;ipython console&gt;&quot;, line 1, in &lt;module&gt;
  ValueError: need more than 1 value to unpack
  
  
  In [40]: for i,j in [test['a'],test['b']]:
     ....:  print i,j
     ....:
  ------------------------------------------------------------
  Traceback (most recent call last):
    File &quot;&lt;ipython console&gt;&quot;, line 1, in &lt;module&gt;
  ValueError: too many values to unpack
  </code></pre>