Get (index,column) pair where the value is True

Question

Say I have a dataframe df

  a        b     c
0 False  True   True
1 False  False  False
2 True   True   False
3 False   False  False

I would like all (index,column) pairs e.g (0,"b"),(0,"c),(2,"a"),(2,"b") where the True value is.

Is there a way to do that, without looping over either the index or columns?

Answer 1

Assuming booleans in the input, you can use:

df.where(df).stack().index.to_list()

output:

[(0, 'b'), (0, 'c'), (2, 'a'), (2, 'b')]

Answer 2

Let us try np.where:

r, c = np.where(df)
[*zip(df.index[r], df.columns[c])]

---

[(0, 'b'), (0, 'c'), (2, 'a'), (2, 'b')]