title: How to deal with SettingWithCopyWarning in Pandas
body: <h2>Background</h2>
  <p>I just upgraded my Pandas from 0.11 to 0.13.0rc1. Now, the application is popping out many new warnings. One of them like this:</p>
  <pre class="lang-none prettyprint-override"><code>E:\FinReporter\FM_EXT.py:449: SettingWithCopyWarning: 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
    quote_df['TVol']   = quote_df['TVol']/TVOL_SCALE
  </code></pre>
  <p>I want to know what exactly it means?  Do I need to change something?</p>
  <p>How should I suspend the warning if I insist to use <code>quote_df['TVol']   = quote_df['TVol']/TVOL_SCALE</code>?</p>
  <h2>The function that gives errors</h2>
  <pre><code>def _decode_stock_quote(list_of_150_stk_str):
      &quot;&quot;&quot;decode the webpage and return dataframe&quot;&quot;&quot;
  
      from cStringIO import StringIO
  
      str_of_all = &quot;&quot;.join(list_of_150_stk_str)
  
      quote_df = pd.read_csv(StringIO(str_of_all), sep=',', names=list('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefg')) #dtype={'A': object, 'B': object, 'C': np.float64}
      quote_df.rename(columns={'A':'STK', 'B':'TOpen', 'C':'TPCLOSE', 'D':'TPrice', 'E':'THigh', 'F':'TLow', 'I':'TVol', 'J':'TAmt', 'e':'TDate', 'f':'TTime'}, inplace=True)
      quote_df = quote_df.ix[:,[0,3,2,1,4,5,8,9,30,31]]
      quote_df['TClose'] = quote_df['TPrice']
      quote_df['RT']     = 100 * (quote_df['TPrice']/quote_df['TPCLOSE'] - 1)
      quote_df['TVol']   = quote_df['TVol']/TVOL_SCALE
      quote_df['TAmt']   = quote_df['TAmt']/TAMT_SCALE
      quote_df['STK_ID'] = quote_df['STK'].str.slice(13,19)
      quote_df['STK_Name'] = quote_df['STK'].str.slice(21,30)#.decode('gb2312')
      quote_df['TDate']  = quote_df.TDate.map(lambda x: x[0:4]+x[5:7]+x[8:10])
      
      return quote_df
  </code></pre>
  <h2>More error messages</h2>
  <pre class="lang-none prettyprint-override"><code>E:\FinReporter\FM_EXT.py:449: SettingWithCopyWarning: 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
    quote_df['TVol']   = quote_df['TVol']/TVOL_SCALE
  E:\FinReporter\FM_EXT.py:450: SettingWithCopyWarning: 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
    quote_df['TAmt']   = quote_df['TAmt']/TAMT_SCALE
  E:\FinReporter\FM_EXT.py:453: SettingWithCopyWarning: 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
    quote_df['TDate']  = quote_df.TDate.map(lambda x: x[0:4]+x[5:7]+x[8:10])
  </code></pre>