title: Python pandas groupby compare lists
body: <p>I have 2 csv files with memberlists that I want to compare.
  As result I would like to have 1 list with all members and an indication in which list they appear and also I would like to calculate the dropout.
  I would like to do this with pandas.</p>
  <p>First file:</p>
  <pre><code>ID,LastName,FirstName,BirthDate
  1,A,a,01/01/1901
  2,B,b,01/01/1902
  3,C,c,01/01/1903
  4,D,d,01/01/1904
  </code></pre>
  <p>Second file:</p>
  <pre><code>ID,LastName,FirstName,BirthDate
  1,A,a,01/01/1901
  4,D,d,01/01/1904
  5,E,e,01/01/1905
  6,F,f,01/01/1906
  </code></pre>
  <p>Result:</p>
  <pre><code>ID,LastName,FirstName,BirthDate,Old,New
  1,A,a,01/01/1901,Yes,Yes
  2,B,b,01/01/1902,Yes,No
  3,C,c,01/01/1903,Yes,No
  4,D,d,01/01/1904,Yes,Yes
  5,E,e,01/01/1905,No,Yes
  6,F,f,01/01/1906,No,Yes
  </code></pre>
  <p>Calculate DropOut:
  Members not in second file / total members in both files</p>