title: Aggregating similar rows in Pandas
body: <p>I've got a dataframe that's currently aggregated by zip code, and looks similar to this:</p>
  <pre><code>Year   Organization   State   Zip      Number_of_people
  
  2021   A              NJ      07090    5
  2020   B              AZ      09876    3
  2021   A              NJ      01234    2
  2021   C              VA      23456    7
  2019   A              NJ      05385    1
  </code></pre>
  <p>I want to aggregate the dataframe and <code>Number_of_People</code> column by state instead, combining identical rows (aside from Number of people) so that the data above instead looks like this:</p>
  <pre><code>Year   Organization   State   Number_of_people
  
  2021   A              NJ      7
  2020   B              AZ      3
  2021   C              VA      7
  2019   A              NJ      1
  </code></pre>
  <p>In other words, if rows are identical in all columns EXCEPT <code>Number_of_people</code>, I want to combine the rows and add the <code>number_of_people</code>.</p>
  <p>I'm stuck on how to approach this problem after deleting the Zip column -- I think I need to group by Year, Organization, and State but not sure what to do after that.</p>