title: How to do "(df1 & not df2)" dataframe merge in pandas?
body: <p>I have 2 pandas dataframes df1 &amp; df2 with common columns/keys (x,y).</p>
  
  <p>I want to merge do a "(df1 &amp; not df2)" kind of merge on keys (x,y), meaning I want my code to return a dataframe containing rows with (x,y) only in df1 &amp; not in df2.</p>
  
  <p>SAS has an equivalent functionality</p>
  
  <pre><code>data final;
  merge df1(in=a) df2(in=b);
  by x y;
  if a &amp; not b;
  run;
  </code></pre>
  
  <p>Who to replicate the same functionality in pandas elegantly?
  It would have been great if we can specify how="left-right" in merge().</p>