Pandas数据帧问题：`reset_index`不会删除分层索引

Question

I am trying to flatten a Pandas Dataframe MultiIndex so that there is only a single level index. The usual solution based on any number of SE posts is to use the df.reset_index command, but that is just not fixing the problem.

I started out with an Xarray DataArray and converted it to a dataframe. The original dataframe looked like this.

                results
      simdata   a_ss_yr attr    attr1   attr2 attr3
run    year                     
 0      0        0      0      0       0       0
        1         1      6     2       0       4
        2         2      4     2       2       0
        3         3      1     0       0       1
        4         4      2     0       2       0

To flatten the index I used

df.reset_index(drop=True)

This only accomplished this:

         run    year  results
simdata               a_ss_yr attr  attr1   attr2
0         0     0      0         0    0    0
1         0     1      1         6    2    0
2         0     2      2         4    2    2
3         0     3      3         1    0    0
4         0     4      4         2    0    2

I tried doing the df.reset_index() option more than once, but this is still not flattening the index, and I want to get this to only a single level index.

More specifically I need the "run" and "year" variables to go to the level 0 set of column names, and I need to remove the "result" heading entirely.

I have been reading the Pandas documentation, but it seems like doing this kind of surgery on the index is not really described. Does anyone have a sense of how to do this?

Answer 1

Use first droplevel for remove first level of MultiIndex and then reset_index :

df.columns = df.columns.droplevel(0)
df = df.reset_index()