title: pandas how to convert all the string value to float
body: <p>I want to convert all the <code>string</code> value in <code>Pandas DataFrame</code> into <code>float</code>, and I can define a short function to do this, but it's not a Pythonic way to do that. My DataFrame looks like this:</p>
  
  <pre><code>&gt;&gt;&gt; df = pd.DataFrame(np.array([['1', '2', '3'], ['4', '5', '6']]))
  &gt;&gt;&gt; df
     0  1  2
  0  1  2  3
  1  4  5  6
  &gt;&gt;&gt; df.dtypes
  0    object
  1    object
  2    object
  dtype: object
  &gt;&gt;&gt; type(df[0][0])
  &lt;type 'str'&gt;
  </code></pre>
  
  <p>I just wonder whether are there some built-in functions of <code>Pandas DataFrame</code> to convert all the <code>string</code> value to <code>float</code>. If you know the built-in function on the Pandas doc, please post the link.</p>