title: SettingWithCopyWarning when modifying a single column in pandas
body: <p>I recently started using pandas for data manipulation. I'm getting the SettingWithCopyWarning when modifying a single column (striping spaces and removing characters) like so:</p>
  
  <pre><code>dframe['title'] = dframe['title'].str.strip()
  dframe['title'] = dframe['title'].str.upper().replace([";", ":"], "", regex=True)
  </code></pre>
  
  <p>Previously I've imported an excel file and used <code>df.iloc[]</code> to select the columns I wanted to work with, and rename the columns. I've already tried assigning that <code>df.iloc[]</code> to a new variable and the warning keeps appearing. Since I'm just starting with pandas, I don't want to ignore the warning right away because, I imagine, there is a better way to do it.</p>
  
  <p><strong>The warning:</strong></p>
  
  <pre><code>See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
    dframe['title'] = dframe['title'].str.upper().replace([";", ":"], "", regex=True)
  c:/file.py:45: SettingWithCopyWarning:
  A value is trying to be set on a copy of a slice from a DataFrame.
  Try using .loc[row_indexer,col_indexer] = value instead
  </code></pre>