title: DataFrame' object has no attribute 'sort'
body: <p>hello~could u help me to solve the questions?</p>
  
  <p>【Anaconda3-4.4.0】</p>
  
  <pre><code>import pandas as pd
  from sqlalchemy import create_engine
  
  engine = create_engine('mysql+pymysql://root:123456@localhost:3306/mysql?charset=utf8')
  sql = pd.read_sql('all_gzdata', engine, chunksize = 10000)
  
  counts = [ i['fullURLId'].value_counts() for i in sql] 
  counts = pd.concat(counts).groupby(level=0).sum() 
  counts = counts.reset_index() 
  counts.columns = ['index', 'num'] 
  counts['type'] = counts['index'].str.extract('(\d{3})') 
  counts_ = counts[['type', 'num']].groupby('type').sum() 
  </code></pre>
  
  <p><strong>the above codes are normal，but if I add the sentence below，python warns“'DataFrame' object has no attribute 'sort'”</strong></p>
  
  <pre><code>counts_.sort('num', ascending = False)
  </code></pre>