title: Converting Fractions in a Dataframe Series to Float
body: <p>In Python 3.x, how can I convert a Dataframe column containing fraction strings and NaN values into floats? I've tried a few things but haven't found an adequate solution.</p>
  
  <p>So if I have a dataframe, "df", that looks like:</p>
  
  <pre><code>     a      b
  0   John   20/1
  1   Bob    NaN
  2   Tim    9/2
  </code></pre>
  
  <p>How can I end up with df looking like:</p>
  
  <pre><code>      a      b
  0   John   20.0
  1   Bob    1000.0
  2   Tim    4.5
  </code></pre>
  
  <p>Thank you for any guidance you're willing to provide!</p>