title: How to drop a row that has a wrong (unknown) value in pandas
body: <p>I am trying to delete a row that has a wrong, but the unknown value in one column.</p>
  
  <p>my data frame looks something like this</p>
  
  <pre><code>'size'  : ['small', 'small', 'medium','small','small'],
  'length': [38, 62, 55,33,22],
  'kinds' : ["A","#$" ,"B","C","A"]}
  </code></pre>
  
  <p>I want to drop the row that has the wrong value. The value is wrong if the value doesn't contain
  any value in kinds</p>
  
  <pre><code>kinds=["A","B","C"]
  </code></pre>
  
  <p>I tried something like this</p>
  
  <pre><code>df[df["kinds"].contains(kinds)]
  </code></pre>
  
  <p>but I couldn't use contains..</p>
  
  <p>What should I do? </p>