title: How to get the max out of a group by on two columns and sum on third in a pandas dataframe?
body: <p>So I used a group by on a pandas dataframe which looks like this</p>
  
  <pre><code>df.groupby(['year','month'])['AMT'].agg('sum')
  </code></pre>
  
  <p>And I get something like this</p>
  
  <pre><code>year  month
  2003  1            114.00
        2           9195.00
        3            300.00
        5            200.00
        6            450.00
        7             68.00
        8            750.00
        9           3521.00
        10           250.00
        11           799.00
        12          1000.00
  2004  1           8551.00
        2           9998.00
        3          17334.00
        4           2525.00
        5          16014.00
        6           9132.00
        7          10623.00
        8           7538.00
        9           3650.00
        10          7733.00
        11         10128.00
        12          4741.00
  2005  1           6965.00
        2           3208.00
        3           8630.00
        4           7776.00
        5          11950.00
        6          11717.00
        7           1510.00
                ...    
  2015  7        1431441.00
        8         966974.00
        9        1121650.00
        10       1200104.00
        11       1312191.90
        12        482535.00
  2016  1        1337343.00
        2        1465068.00
        3        1170113.00
        4        1121691.00
        5        1302936.00
        6        1518047.00
        7        1251844.00
        8         825215.00
        9        1491626.00
        10       1243877.00
        11       1632252.00
        12        750995.50
  2017  1         905974.00
        2        1330182.00
        3        1382628.52
        4        1146789.00
        5        1201425.00
        6        1278701.00
        7        1172596.00
        8        1517116.50
        9        1108609.00
        10       1360841.00
        11       1340386.00
        12        860686.00
  </code></pre>
  
  <p>What I want is to just select the max out of the third summed column so that the final data frame has only the max from each year, something like:</p>
  
  <pre><code>year  month
  2003      2           9195.00
  2004      3          17334.00
  2005      5          11950.00
  </code></pre>
  
  <p>... and so on</p>
  
  <p>What do I have to add to my group by aggregation to do this?</p>