title: Issues iterating dataframe in pandas
body: <p>I am filling out a dataframe using the content of a list of lists such as:</p>
  
  <pre><code>desc_prep=[['aesthet', 'abod'], [['arb', 'abod'], ['forest', 'abod']]]
  
  col_names =  ['desc_name','desc_avg_vector']
  df_desc_prep = pd.DataFrame(columns=col_names)    
  df_desc_prep['desc_name']=desc_prep
  </code></pre>
  
  <p>At this point of time I am getting the following:</p>
  
  <pre><code>                         desc_name
  0                [aesthet, abod]
  1  [[arb, abod], [forest, abod]]
  </code></pre>
  
  <p>When iterating the dataframe with iteritems to get a tuple with the column name and the content as a Series:</p>
  
  <pre><code>for index, value in df_desc_prep.iteritems():
      print("index: ", index)#--&gt;index:  desc_name
      print("value: ", value)#--&gt;value:  0                  [aesthet, abod]
      print("value[0]:", value[0])#['aesthet', 'abod']
      print("value[1]:", value[1])#[['arb', 'abod'], ['forest', 'abod']]
      if isinstance(value[0], list):#-&gt;value[0]:  ['aesthet', 'abod']
  </code></pre>
  
  <p>When iterating using iterrows() to get a Series for each row:</p>
  
  <pre><code>for index, value in df_desc_prep.iterrows():
      print("index: ", index)#--&gt;index:  0
      print("value: ", value)#--&gt;value:  desc_name    [aesthet, abod]
      if isinstance(value[0], list):#--&gt;value[0]:  ['aesthet', 'abod'], value[1]: IndexError: index out of bounds
  </code></pre>
  
  <p>I was expecting to get value[0] as <code>aesthet</code> and value[1] as <code>abod</code>. Instead I am getting <code>IndexError: index out of bounds</code> when getting value[1].</p>
  
  <p>How can I get the behaviour of iterating over the dataframe and getting <code>value[0]=aesthet</code> when iterating over <code>['aesthet', 'abod']</code> and <code>value[0]=['arb', 'abod']</code> when iterating over <code>[['arb', 'abod'], ['forest', 'abod']]</code></p>