title: Why does not work pandas df.loc + lambda?
body: <p>I have created pandas frame from csv file.
  And I want to select rows use lambda.
  But it does not work.
  I use <a href="http://pandas.pydata.org/pandas-docs/stable/indexing.html#selection-by-callable" rel="nofollow noreferrer">this pandas manual</a>.
  <a href="https://i.stack.imgur.com/mR6li.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mR6li.jpg" alt="enter image description here"></a>
  exception: 
  <a href="https://i.stack.imgur.com/WMBFb.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WMBFb.jpg" alt="enter image description here"></a></p>
  
  <p>what is problem?
  thanks.</p>