title: Comparing dataframe datetime column value in Python?
body: <p>I am new to Pandas. 
  I have the following pandas dataframe which contains the following values :</p>
  
  <pre><code>index print_statement      timestamp 
  0     echo "I AM HAPPY2" 2018-11-12 08:01:00       
  1     echo "I AM HAPPY3" 2018-11-12 08:01:00       
  2     echo "I AM HAPPY1" 2018-11-12 08:01:00       
  3     echo "I AM HAPPY4" 2018-12-12 08:02:00      
  4     echo "I AM HAPPY5" 2018-12-13 08:02:00  
  </code></pre>
  
  <p>I want to compare the df as: 
   - let's say I have a time_argument which is <code>datetime.datetime(2018, 12, 12, 5, 1)</code>. I want to store the result in another <code>dataframe</code> where timestamp > time_argument. </p>
  
  <p>I tried using the following approach: </p>
  
  <pre><code>for index, row in df.iterrows():
       date_store = row['time_to_expire']
       if date_store.to_pydatetime() &gt;= ii:
           df_final = row
  </code></pre>
  
  <p>But I am not getting the desired answer. </p>
  
  <p>Hope I am clear with the question. </p>