Pandas df return indices of duplicated elements as a list

Question

I’d like to have the indexes of duplicated column elements as a list. So far, the way I found is

test = ['a', 'a', 'b', 'c', 'b']
testdf = pd.DataFrame(test, columns=['test'])
np.asarray(np.where(list(testdf['test'].duplicated()))).tolist()[0]
# [1, 4]

Which seems ridiculously convoluted.

Any better way?

Asked By: gaut

||

Source

Answer 1

Try this just indexing the index:

testdf.index[testdf['test'].duplicated()]

add to_list:

testdf.index[testdf['test'].duplicated()].to_list()

Output:

[1, 4]

Answered By: Scott Boston

Answer 2

you can use .duplicated() with .tolist()

testdf.index[testdf.test.duplicated()].tolist()

Answered By: bitflip

Answer 3

%%time

test = ['a', 'a', 'b', 'c', 'b']
testdf = pd.DataFrame(test, columns=['test'])
testdf[testdf.test.duplicated()].index.to_list()

# Wall time: 2 ms
# [1, 4]

Answered By: Sumaia A

Pandas df return indices of duplicated elements as a list

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