pandas对指定列进行填充的方法

实例如下所示： >>> import pandas as pd >>> import numpy as np >>> ts1 = [0, 1, np.nan, np.nan, np.nan, np.nan] >>> ts2 = [0, 2, np.nan, 3, np.nan, np.nan] >>> d = {'X': ts1, 'Y': ts2, 'Z': ts2} >>> df = pd.DataFrame(data=d) >>> df X Y Z 0 0.0 0.0 0.0 1 1.0 2.0 2.0 2 NaN NaN NaN 3 NaN 3.0 3.0 4 NaN Na