我如何总结所有值取决于熊猫中的索引值？

Question

I want to calculate some values between type1 and type2 elements. For example if have index like: (a,b) and (b,a) then it will equals to (a,b)+(b,a) I want to sum values if reverse indexes exists.

Answer 1

One way using frozenset :

df = df.reset_index()
df['total'].groupby(df[['type1', 'type2']].apply(frozenset, 1)).sum()

Output:

(b, a)    15
(c, a)    19
Name: total, dtype: int64

Answer 2

Let df be your DataFrame. Swap the first and second levels of the MultiIndex, concatenate the original and the new DataFrames, and calculate row sums:

pd.concat([df, df.swaplevel()], axis=1).sum(1)
#a  b    15
#   c    19
#b  a    15
#c  a    19

The solution works even for the rows that do not have matching reversed rows. The answer has duplicated rows for the direct and the reversed index. You will have to filter out the unwanted rows.