title: Set value to an entire column of a pandas dataframe
body: <p>I'm trying to set the entire column of a dataframe to a specific value.</p>
  
  <pre><code>In  [1]: df
  Out [1]: 
       issueid   industry
  0        001        xxx
  1        002        xxx
  2        003        xxx
  3        004        xxx
  4        005        xxx
  </code></pre>
  
  <p>From what I've seen, <code>loc</code> is the best practice when replacing values in a dataframe (or isn't it?):</p>
  
  <pre><code>In  [2]: df.loc[:,'industry'] = 'yyy'
  </code></pre>
  
  <p>However, I still received this much talked-about warning message:</p>
  
  <pre><code>A value is trying to be set on a copy of a slice from a DataFrame.
  Try using .loc[row_index,col_indexer] = value instead
  </code></pre>
  
  <p>If I do</p>
  
  <pre><code>In  [3]: df['industry'] = 'yyy'
  </code></pre>
  
  <p>I got the same warning message.</p>
  
  <p>Any ideas?  Working with Python 3.5.2 and pandas 0.18.1.</p>