CODEWITHSUNDEEP
pythonpandas
chthonicdaemon
chthonicdaemon

Reputation: 19800

Accessing pandas multi-index with a variable

I'm struggling to access a Pandas DataFrame with a multi-index programatically. Let's say I have 

import pandas as pd

df = pd.DataFrame([[0, 0, 0, 1],
                  [0, 0, 1, 2], 
                  [0, 1, 0, 7],
                  [0, 1, 1, 9],
                  [1, 0, 0, 1],
                  [1, 0, 1, 0],
                  [1, 1, 0, 1],
                  [1, 1, 1, 10]], columns=['c1', 'c2', 'c3', 'value'])

sums = df.groupby(['c1', 'c2', 'c3']).value.sum()

I can get the sum which corresponds to the [1, 1, 1] combination of c1, c2 and c3 with

sums[1, 1, 1]

That returns 10 as expected.

But what if I have a variable 

q = [1, 1, 1]

how do I get the same value out?

I have tried

sums[q]

which gives

c1  c2  c3
0   0   1     2
        1     2
        1     2
Name: value, dtype: int64

Also I thought star operator could work:

sums[*q]

but that is invalid syntax.

Upvotes: 2

Views: 333

Answers (1)

jezrael
jezrael

Reputation: 863146

Use Series.xs with tuple:

print (sums.xs((1,1,1)))
10

Or Series.loc:

print (sums.loc[(1,1,1)])
#alternative
#print (sums[(1,1,1)])
10

q = [1, 1, 1]
print (sums.loc[tuple(q)])
#alternative
#print (sums[tuple(q)])
10

Upvotes: 1

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