title: sort excel columns using pandas
body: <p>I want to sort the excel file  worksheet called "LTE_PrbUtil" and it has a column called "CELL" which is string descending. 
  When I run the program and find some error:</p>
  
  <pre><code>  File "C:\Users\p4532\Desktop\QGIS_project\highloading.py", line 18, in &lt;module&gt; df = df.sort(columns="CELL")
    File "C:\Python27\lib\site-packages\pandas\core\generic.py", line 3081, in __getattr__
      return object.__getattribute__(self, name)
  AttributeError: 'DataFrame' object has no attribute 'sort'`
  </code></pre>
  
  <p>Here is my code: </p>
  
  <pre><code>import shutil
  import pandas as pd
  import xlrd
  xl=pd.ExcelFile("C:\Users\p4532\Desktop\QGIS_project\HighUtilCells_new.xlsx")                                                                           
  df = xl.parse("LTE_PrbUtil")
  df = df.sort(columns="CELL")
  </code></pre>
  
  <p>It seems the dataframe cannot recognize <code>sort</code>.
  Can anyone help?</p>