title: How to filter dataframe by columns values combinations?
body: <p>I have a dataframe:</p>
  <pre><code>col1   col2   col3
  a       b       b
  a       b       c
  k       l       o
  b       l       b
  </code></pre>
  <p>I want to keep only rows where col1 is &quot;a&quot;, col2 is &quot;b&quot; and col3 is &quot;b&quot; or col1 is &quot;k&quot;, col2 is &quot;l&quot; and col3 is &quot;o&quot;. So desired result is:</p>
  <pre><code>col1   col2   col3
  a       b       b
  k       l       o
  
  </code></pre>
  <p>How to do that? i can write <code>dt[(dt[&quot;col1&quot;]==&quot;a&quot;)&amp;(dt[&quot;col2&quot;]==&quot;b&quot;)&amp;(dt[&quot;col1&quot;]==&quot;b&quot;)]</code> but what about second case? should i put it with or?</p>