title: A simple log of a dataframe in python : Error : 'type' object does not support item assignment
body: <p>I am trying to take a log of a dataframe and copy it into a new dataframe in Python and I  get this error : 'type' object does not support item assignment</p>
  
  <pre><code>import math
  y = pd.DataFrame
  y['Number'] = np.log(df.Number)
  y
  </code></pre>