title: Python filter rows in dataframe by date
body: <p>I have a dataframe in the following format: </p>
  
  <pre><code>month     count
  2015/01   100
  2015/02   200
  2015/03   300
  ...
  </code></pre>
  
  <p>And want to get a new dataframe which contains month greater than a month, e.g.. 2015/03. </p>
  
  <p>I tried to use the following code: </p>
  
  <pre><code>sdf = df.loc[datetime.strptime(df['month'], '%Y-%m')&gt;=datetime.date(2015,9,1,0,0,0)]
  </code></pre>
  
  <p>I'm new to Python. Really appreciate it if some one can help. </p>