title: Print value from a list (The truth value of a DataFrame is ambiguous error)
body: <p>Having a question. I am having a list of records and there is another list of records which i am comparing the first list. 
  When i write line(inside row reading of first list:</p>
  
  <pre><code>    for index, row in output_merged_po.iterrows():
          stock = output_merged_stock[output_merged_stock['PN_STRIPPED']==row['PN_STRIPPED']][['Whs']]
          print stock
  </code></pre>
  
  <p>I get result</p>
  
  <pre><code>       Whs
   11763 VLN
  </code></pre>
  
  <p>Where 11763 is output_merged_stock id number and Whs is name of whs where PN_stripped matches.</p>
  
  <p>But i fail to extract data for further processing. I just want to write simple if statetement where i can ask if <code>whs = VLN</code>. I wrote:</p>
  
  <pre><code>                    if stock[['Whs']] == 'VLN':
                           print stock
  </code></pre>
  
  <p>I got error: <code>The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().</code></p>
  
  <p>I wrote:</p>
  
  <pre><code>                    if stock == 'VLN':
                          print stock
  </code></pre>
  
  <p>And i got again : <code>The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().</code></p>
  
  <p>How should i write if statement if i want to get result 'VLN'? As for example there are sometimes cases when stock output is sometimes 3 whs, where 2 of them are 'VLN' and third is 'XRS' and on that case i should see of 'if' output 2 times VLN without XRS</p>