title: find which row has a string
body: <p>I am using pandas and I have a column that has numbers but when I check for datatype I get the column is an object. I think one of the rows in that column is actually a string. How can I find out which row is the string? For example:</p>
  
  <pre><code>Name    A    B
  John    0    1
  Rich    1    0
  Jim     O    1
  </code></pre>
  
  <p>Jim has the letter "O" instead of zero on column A.  what can I use in pandas to find which row has the string instead of the number if I have thousands of rows? In this example I used the letter O, but it could be any letter, really.  </p>