title: Pandas, how can cast a column as floats that hold floats, strings, and strings that cannot be converted?
body: <p>Let's say I have the following pandas df:</p>
  <pre><code>a = [['a', 0.1], ['b', ' 0.2'], ['c', '0.2,0.3']]
  df = pd.DataFrame(a, columns= ['alphabet', 'floats'])
  
  
  &gt;&gt;&gt; df
    alphabet   floats
  0        a      0.1
  1        b      0.2
  2        c  0.2,0.3
  </code></pre>
  <p>And I wish to remove all rows in which the value of the column floats cannot be cast as float and cast all values as float that can be cast as such:</p>
  <pre><code>&gt;&gt;&gt; df
    alphabet   floats
  0        a      0.1
  1        b      0.2
  </code></pre>