title: Python (Pandas) Add subtotal on each lvl of multiindex dataframe
body: <p>Assuming I have the following dataframe: </p>
  
  <pre><code>a       b       c      Sce1     Sce2    Sce3    Sce4    Sce5    Sc6
  Animal  Ground  Dog    0.0      0.9     0.5     0.0     0.3     0.4  
  Animal  Ground  Cat    0.6      0.5     0.3     0.5     1.0     0.2 
  Animal  Air     Eagle  1.0      0.1     0.1     0.6     0.9     0.1 
  Animal  Air     Owl    0.3      0.1     0.5     0.3     0.5     0.9     
  Object  Metal   Car    0.3      0.3     0.8     0.6     0.5     0.6 
  Object  Metal   Bike   0.5      0.1     0.4     0.7     0.4     0.2 
  Object  Wood    Chair  0.9      0.6     0.1     0.9     0.2     0.8 
  Object  Wood    Table  0.9      0.6     0.6     0.1     0.9     0.7 
  </code></pre>
  
  <p>I want to create a MultiIndex, which will contain the sum of each lvl. The output will look like this: </p>
  
  <pre><code>a      b      c     Sce1    Sce2    Sce3    Sce4    Sce5    Sce6
  Animal              1.9     1.6     1.4     1.3     2.7     1.6 
         Ground       0.6     1.4     0.8     0.5     1.3     0.6 
                Dog   0.0     0.9     0.5     0.0     0.3     0.4 
                Cat   0.6     0.5     0.3     0.5     1.0     0.2 
         Air          1.3     0.2     0.7     0.8     1.4     1.0 
                Eagle 1.0     0.1     0.1     0.6     0.9     0.1 
                Owl   0.3     0.1     0.5     0.3     0.5     0.9 
  Object              2.6     1.6     1.8     2.3     2.0     2.3 
         Metal        0.8     0.3     1.1     1.3     0.9     0.8 
                Car   0.3     0.3     0.8     0.6     0.5     0.6 
                Bike  0.5     0.1     0.4     0.7     0.4     0.2 
         Wood         1.8     1.3     0.6     1.0     1.1     1.5 
                Chair 0.9     0.6     0.1     0.9     0.2     0.8 
                Table 0.9     0.6     0.6     0.1     0.9     0.7 
  </code></pre>
  
  <p>At the moment I am using a loop to create three different dataframes on each level and then manipulate them on excel, as below. So I wanted to take this calculation in python if possible.</p>
  
  <pre><code>for i in range range(0,3):
      df = df.groupby(list(df.columns)[0:lvl], as_index=False).sum()
      return df
  </code></pre>
  
  <p>Many thanks in advance. </p>