Pandas - fill value in new column based on which column is not empty

Question

I have a dataframe like this:

	a	b	c	d
1		0.325
2			0.23378
3		2.3242
4	0.42
5	6.293

The four columns represent different water depths and the values are temperature measurements. There is only one non-NA value in the four columns a, b, c, d. I want to aggregate the values into one column value (or water temperature) and the 'position' of the value, ie the associated column name in a new column (or water depth) column.

Expected output format:

	value	column
1	0.325	b
2	0.23378	c
3	2.3242	b
4	0.42	a
5	6.293	a

Answer 1

Use DataFrame.stack with DataFrame.rename_axis :

df = df.stack().rename_axis(['value','column']).reset_index()