piRSquared piRSquared - 6 months ago 63
Python Question

collapse a pandas MultiIndex

Suppose I have a

DataFrame
with
MultiIndex
columns. How can I collapse the levels to a concatenation of the values so that I only have one level?

Setup



np.random.seed([3, 14])
col = pd.MultiIndex.from_product([list('ABC'), list('DE'), list('FG')])
df = pd.DataFrame(np.random.rand(4, 12) * 10, columns=col).astype(int)

print df

A B C
D E D E D E
F G F G F G F G F G F G
0 2 1 1 7 5 9 9 2 7 4 0 3
1 3 7 1 1 5 3 1 4 3 5 6 0
2 2 6 9 9 9 5 7 0 1 2 7 5
3 2 2 8 0 3 9 4 7 0 8 2 5


I want the result to look like this:

ADF ADG AEF AEG BDF BDG BEF BEG CDF CDG CEF CEG
0 2 1 1 7 5 9 9 2 7 4 0 3
1 3 7 1 1 5 3 1 4 3 5 6 0
2 2 6 9 9 9 5 7 0 1 2 7 5
3 2 2 8 0 3 9 4 7 0 8 2 5

Answer

you may try this:

In [200]: cols = pd.Series(df.columns.tolist()).apply(pd.Series).sum(axis=1)

In [201]: cols
Out[201]:
0     ADF
1     ADG
2     AEF
3     AEG
4     BDF
5     BDG
6     BEF
7     BEG
8     CDF
9     CDG
10    CEF
11    CEG
dtype: object
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