[python] Python Pandas : group by in group by and average?

I have a dataframe like this:

cluster  org      time
   1      a       8
   1      a       6
   2      h       34
   1      c       23
   2      d       74
   3      w       6 

I would like to calculate the average of time per org per cluster.

Expected result:

cluster mean(time)
1       15 ((8+6)/2+23)/2
2       54   (74+34)/2
3       6

I do not know how to do it in Pandas, can anybody help?

I would simply do this, which literally follows what your desired logic was:

df.groupby(['org']).mean().groupby(['cluster']).mean()