title: AttributeError: 'list' object has no attribute 'reset_index'
body: <p>I'm pretty darn new to pandas and I'm having issues with using group by. I'm trying to group by e.g., car model and car values.   I wanted it to output the average or mean price for each car model..</p>
  
  <pre><code>model    price
  ------   ----
  honda     2000
  Toyota    3000
  </code></pre>
  
  <pre><code>file = pd.read_csv('file.csv')
  file2 = pd.read_csv('file2.csv')
  
  file2['price'] = file2['price'].replace('#','')
  file['price'] = file['price'].replace('#','')
  
  new = pd.merge(file,file2, on=['col'])
  
  new.drop(['cols'],inplace=True,axis=1)
  
  **new.groupby(['car','price'].reset_index().groupby(['price']).mean(),as_index=True)**
  
  </code></pre>
  
  <p>I keep getting the error: AttributeError: 'list' object has no attribute 'reset_index'</p>
  
  <p>I originally tried this:</p>
  
  <pre><code>new.groupby(['car']).groupby(['price']).mean()
  </code></pre>
  
  <p>But it was throwing a: <code>Cannot access callable attribute 'groupby' of 'DataFrameGroupBy' objects, try using the 'apply' method</code></p>