title: Pandas: AttributeError: 'str' object has no attribute 'iloc'
body: <p>I need to convert columns from unicode to str.
  I try</p>
  
  <pre><code>f.edge(str(group['subdomain']).iloc[i], str(group['subdomain'].iloc[i+1]),
             label=str(group['search_term'].iloc[i+1]))
  </code></pre>
  
  <p>But it returns <code>AttributeError: 'str' object has no attribute 'iloc'</code>
  How can I fix that?</p>