title: What is the analogue of EXCEPT clause in SQL in Pandas?
body: <p>I have a sample pandas dataframe df:</p>
  
  <pre><code>        col1    col2    col3    col4
        0   a      1.0    2.0      3
        1   b      NaN    NaN      6
        2   c      NaN    8.0      9
        3   d      NaN    11.0    12
        4   e     13.0    14.0    15
        5   f     17.0    18.0    19
        6   g     21.0    22.0    23
  </code></pre>
  
  <p>and a second one df1:</p>
  
  <pre><code>        col1    col2    col3    col4
        0  a      1.0     2.0      3
        4  e     13.0    14.0     15
        5  f     17.0    18.0     19
        6  g     21.0    22.0     23
  </code></pre>
  
  <p>I want to get the subset of df that does not overlaps with df1.  In effect I am looking for the equivalent of the EXCEPT operand in SQL.</p>
  
  <p>I used the subtract() function -- but this was clearly wrong, as the subtract performs elementwise numerical subtraction.  So I got an error message:</p>
  
  <pre><code>       TypeError: unsupported operand type(s) for -: 'str' and 'str'
  </code></pre>
  
  <p>So the question is: What is the equivalent of EXCEPT in SQL for Pandas?</p>