To find out a header and index of a particular value in a multi-columned dataframe

Question

I am working on a Pandas Dataframe which has boolean values in it's cells. I want to find out the header and index of all cells in the dataframe where the value is False (Expected output is header_index )

df_sample=pandas.DataFrame([[True,True,False,True],[False,True,False,True],[True,True,True,True],[False,True,True,True]],columns=['ColumnA','ColumnB','ColumnC','ColumnD'])

   ColumnA  ColumnB  ColumnC  ColumnD
0     True     True    False     True
1    False     True    False     True
2     True     True     True     True
3    False     True     True     True

My expected output is:

ColumnC_0
ColumnA_1
ColumnC_1

I have tried multiple iterations using loc and iloc but unable to come up with this formatted output A logical idea on how to approach this would help

Answer 1

Use DataFrame.stack to reshape the dataframe df_sample into a MultiIndex series s , then use boolean masking to filter the series next use map to flatten the MultiIndex to get the desired list:

s = (~df_sample).stack()
idx = s[s].index.map(lambda s: f'{s[1]}_{s[0]}').tolist()

Result:

print(idx)
['ColumnC_0', 'ColumnA_1', 'ColumnC_1', 'ColumnA_3']