title: TypeError: conversion from Series to Decimal is not supported
body: <p>Any ideas on how to convert a series (column) from float to decimal? I am on Python 3.6. I have read the Decimal documentation, but it offers no help.</p>
  
  <pre><code>df['rate'].dtype
  Out[158]: dtype('float64')
  Decimal(df['rate'])
  Traceback (most recent call last):
    File "C:\Users\user\Anaconda3\lib\site-packages\IPython
     \core\interactiveshell.py", line 2862, in run_code
      exec(code_obj, self.user_global_ns, self.user_ns)
      File "&lt;ipython-input-159-88710e11f7cd&gt;", line 1, in &lt;module&gt;
      Decimal(df['rate'])
   TypeError: conversion from Series to Decimal is not supported
  </code></pre>