Sum column in multi-level pandas dataframe

Question

I have been looking at stack overflow questions to solve this problem but I haven't found a solution.

I have a dataframe df that looks like this:

            value
pod         22          72          79          86         87          88   
time_stamp                                          
2016-10-03  10.160000   0.000000    0.000000    32.004001   5.334000    11.176000   
2016-10-10  0.000000    0.000000    0.000000    2.032000    0.000000    0.000000    
2016-10-17  16.002001   0.000000    8.636000    21.336001   1.778000    6.604000    
2016-10-24  2.032000    6.604000    71.628004   19.050001   0.508000    2.540000    
2016-10-31  3.556000    21.590000   0.000000    0.000000    2.032000    2.794000    
2016-11-07  3.302000    10.160000   0.762000    0.254000    1.270000    2.540000    
2016-11-14  27.686001   44.704001   22.606001   1.524000    26.670001   42.164001   
2016-11-21  68.072001   56.896002   14.732000   8.128000    23.114001   63.500002   

The output when I do df.head(5).to_dict() looks like this:

{('value', 22): {Timestamp('2016-10-03 00:00:00'): 10.159999966599999,
Timestamp('2016-10-10 00:00:00'): 0.0,
Timestamp('2016-10-17 00:00:00'): 16.0020005107,
Timestamp('2016-10-24 00:00:00'): 2.0320000648500001, 
Timestamp('2016-10-31 00:00:00'): 3.5560001134900006},
('value', 72): {Timestamp('2016-10-03 00:00:00'): 0.0,
Timestamp('2016-10-10 00:00:00'): 0.0,
Timestamp('2016-10-17 00:00:00'): 0.0,
Timestamp('2016-10-24 00:00:00'): 6.6040000915499997,
Timestamp('2016-10-31 00:00:00'): 21.589999973800001},
('value', 79): {Timestamp('2016-10-03 00:00:00'): 0.0,
Timestamp('2016-10-10 00:00:00'): 0.0,
Timestamp('2016-10-17 00:00:00'): 8.6360000968000001,
Timestamp('2016-10-24 00:00:00'): 71.628004074100005,
Timestamp('2016-10-31 00:00:00'): 0.0},

I want to groupby the column and sum all the values. I'm getting stuck because this seems to be a multi-level index.

When I do this s = df.sum(axis=1, level=[1]); s s = df.sum(axis=1, level=[1]); s it just removes the first row: value . How do I get the columns summed instead?

The output could just be a simple dataframe that sums the value column so it could look something like:

pod    22    72    79...
2016   100   120   110...
2017   80    90    72...

Answer 1

It seems you need sum along the 0 ^th axis:

df

                value                   
                   22      72         79
2016-10-03  10.160000   0.000   0.000000
2016-10-10   0.000000   0.000   0.000000
2016-10-17  16.002001   0.000   8.636000
2016-10-24   2.032000   6.604  71.628004
2016-10-31   3.556000  21.590   0.000000

df.sum(axis=0).to_frame().T

       value                   
          22      72         79
0  31.750001  28.194  80.264004

---

If you want a grouping operation by year, call groupby on index.year :

df.groupby(df.index.year).sum()

          value                   
             22      72         79
2016  31.750001  28.194  80.264004