CODEWITHSUNDEEP
pythonlistpandasindexing
The Nightman
The Nightman

Reputation: 5759

Get one index from multiindexed dataframe

If I have a multiindexed dataframe, how can i get the information in just one of the indexes?

If my df is this:

first  second
bar    one       0.469112
       two      -0.282863
baz    one      -1.509059
       two      -1.135632
foo    one       1.212112
       two      -0.173215
qux    one       0.119209
       two      -1.044236

I would like a list of the values in index first. I'm used to doing something like this:

df.index.tolist()

which returns:

['bar','baz','foo','qux']

Upvotes: 1

Views: 47

Answers (2)

BENY
BENY

Reputation: 323226

Data from jpp

df.index.levels[0]
Out[412]: Index(['A', 'X'], dtype='object', name='idx1')

Update : 

[x[0] for x in df.index.tolist()]
Out[417]: ['A', 'A', 'X', 'X']

Upvotes: 3

jpp
jpp

Reputation: 164673

You can use pd.Index.get_level_values. Here's a demo:

df = pd.DataFrame([['A', 'B', 1], ['A', 'C', 2], ['X', 'Y', 3], ['X', 'Z', '4']],
                  columns=['idx1', 'idx2', 'value'])

df = df.set_index(['idx1', 'idx2'])

res = df.index.get_level_values(0).tolist()

['A', 'A', 'X', 'X']

Upvotes: 4

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