根据另一个Pandas DataFrame中的值替换Pandas DataFrame中缺少的值

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, None, 4, 5],
                    'B': [None, 6, 7, None, 9],
                    'C': [10, 11, 12, 13, None]})

df2 = pd.DataFrame({'A': [100, 200, 300],
                    'B': [400, 500, 600],
                    'C': [700, 800, 900]})

df1_filled = df1.fillna(df2)

print(df1_filled)

       A      B      C
0    1.0  400.0   10.0
1    2.0    6.0   11.0
2  300.0    7.0   12.0
3    4.0  500.0   13.0
4    5.0    9.0  900.0