title: How to get the index value in a dataframe by comparing date with a datetime object in that dataframe?
body: <p>I have a dataframe like the following. I would like to get the index value by checking the date. For example if the date is 2018-04-05, I need to get the index value as 3. Can someone let me know how to do that? </p>
  
  <pre><code>       close                      date     high      low     open   volume
  0    1536.95 2018-04-02 09:15:00+05:30  1545.00  1509.40  1509.40   420761   
  1    1554.80 2018-04-03 09:15:00+05:30  1562.00  1534.00  1534.00   201412   
  2    1530.00 2018-04-04 09:15:00+05:30  1576.85  1525.85  1554.00   171614   
  3    1552.35 2018-04-05 09:15:00+05:30  1559.70  1536.90  1551.40   198303   
  4    1553.25 2018-04-06 09:15:00+05:30  1560.95  1542.85  1558.00   119196   
  5    1541.30 2018-04-09 09:15:00+05:30  1559.15  1535.65  1552.90   175732   
  6    1539.15 2018-04-10 09:15:00+05:30  1555.90  1531.45  1555.90   112086   
  7    1533.55 2018-04-11 09:15:00+05:30  1543.50  1520.10  1531.90   319761   
  </code></pre>