title: Pandas Series to json and back
body: <p>I have some problems converting a simple Pandas Series into a json string and back. Here's my attempt</p>
  
  <pre><code>import pandas as pd
  f = pd.Series(data=[1.0,2.0,3.0],index=[10,20,30])
  x = f.to_json()
  a = pd.read_json(x)
  </code></pre>
  
  <p>This results in ValueError: If using all scalar values, you must pass an Index.</p>
  
  <p>The json String x looks like
  {"10":1.0,"20":2.0,"30":3.0}</p>
  
  <p>What's missing here. Please help</p>