Pandas return index and column name based on condition

Question

Let's say we have a DataFrame:

df = pd.DataFrame({
    'D': {'A': 0.810032, 'B': 0.752299, 'C': 0.224038},
    'E': {'A': 0.17714, 'B': 0.680405, 'C': 0.769732},
    'F': {'A': 0.942959, 'B': 0.436582, 'C': 0.269791}
})
print(df)
          D         E         F
A  0.810032  0.177140  0.942959
B  0.752299  0.680405  0.436582
C  0.224038  0.769732  0.269791

Is it possible to return index and column names into a list of tuples based on a condition, for instance

print(df < 0.25)
   D      E      F
A  False   True  False
B  False  False  False
C  True  False  False

I would like to end up with a list of tuples like:

[('A','E'),('C','D')]

try : A.lt(.25).stack().loc[lambda df: df].index.to_list() — sammywemmy
– sammywemmy, Commented Nov 4, 2021 at 23:32
@DHJ Please do not edit your question to include the answer (Questions and Answers should be separate on SO). Just notify the commenter and ask them if they would like to post that as an answer like I did. — Henry Ecker
– Henry Ecker ♦, Commented Nov 4, 2021 at 23:54

Henry Ecker · Accepted Answer · 2021-11-05 00:02:23Z

4

We can also use DataFrame.where then stack which takes advantage of the fact that stack drops NaN values by default then use Index.tolist to get the list of tuples:

results = df.where(df < .25).stack().index.tolist()

results:

[('A', 'E'), ('C', 'D')]

answered Nov 5, 2021 at 0:02

Henry Ecker♦

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Comments

sammywemmy · Accepted Answer · 2021-11-04 23:54:19Z

3

One option is to reshape the data and filter with the booleans:

df.lt(.25).stack().loc[lambda df: df].index.to_list()

[('A', 'E'), ('C', 'D')]

edited Nov 4, 2021 at 23:54

answered Nov 4, 2021 at 23:51

sammywemmy

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