📅  最后修改于: 2022-03-11 14:45:18.783000             🧑  作者: Mango
>>> df = pd.DataFrame([[1, 2, 3], [4, None, None], [None, None, 9]])
>>> df.fillna(method='ffill')
0 1 2
0 1 2 3
1 4 2 3
2 4 2 9