Python-сообщество

print df
                  height weight
gender group  age              
male   group1 6     0.19   0.59
              7     0.26   0.49
       group2 6     0.74   0.49
              7     0.87   0.39
female group1 6     0.36   0.97
              7     0.08   0.36
       group2 6     0.17   0.20
              7     0.36   0.13

print df.xs(6, level='age')
              height weight
gender group               
male   group1   0.12   0.41
       group2   0.49   0.88
female group1   0.00   0.54
       group2   0.62   0.99

gender  group   age
male    group1  6      0.37
                7      0.42
        group2  6      0.12
                7      0.85
female  group1  6      0.56
                7      0.67
        group2  6      0.55
                7      0.94