df = pd.DataFrame({
'from': ['Start', '21', '73', 'Start', '55', '1', '2', '3'],
'to': ['21', '73', '55', '1', '54', '2', '3', '4']
})
| from | to | |
|---|---|---|
| 0 | Start | 21 |
| 1 | 21 | 73 |
| 2 | 73 | 55 |
| 3 | Start | 1 |
| 4 | 55 | 54 |
| 5 | 1 | 2 |
| 6 | 2 | 3 |
| 7 | 3 | 4 |
desired output
[['Start', '21', '73', '55', '54'], ['Start', '1', '2', '3', '4']]
the rows don’t have to be in the correct order, as for 55, 54.