Python 使用 Pandas 将数据框中的值替换为另一个数据框中的值

我有两个数据帧，具有相同的列，但不同的值和不同的行数.

import pandas as pd

data1 = {'Region': ['Africa','Africa','Africa','Africa','Africa','Africa','Africa','Africa','Asia','Asia','Asia','Asia'],
         'Country': ['South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','Japan','Japan','Japan','Japan'],
         'Product': ['ABC','ABC','ABC','ABC','XYZ','XYZ','XYZ','XYZ','DEF','DEF','DEF','DEF'],
         'Year': [2016, 2017, 2018, 2019,2016, 2017, 2018, 2019,2016, 2017, 2018, 2019],
         'Price': [500, 400, 0,450,750,0,0,890,500,470,0,415]}

data1 = {'Region': ['Africa','Africa','Africa','Africa','Africa','Africa','Asia','Asia'],
         'Country': ['South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','Japan','Japan'],
         'Product': ['ABC','ABC','ABC','ABC','XYZ','XYZ','DEF','DEF'],
         'Year': [2016, 2017, 2018, 2019,2016, 2017,2016, 2017],
         'Price': [200, 100, 30,750,350,120,400,370]}

df = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

df是完整的数据集，但有一些旧值，而df2只有更新的值.我想用df2中的值替换df中的所有值，同时保持不在df2中的值从df开始.

例如，在df中，Country=日本，Product=DEF，在Year=2016中，Price应该从470更新为400.2017年保持不变，2018年和2019年保持不变.

到目前为止，我有以下代码似乎不起作用:

common_index = ['Region','Country','Product','Year']
df = df.set_index(common_index)
df2 = df2.set_index(common_index)
df.update(df2, overwrite = True)

但这只会用df2的值更新df，并删除其他所有内容.

预期输出应如下所示:

data3 = {'Region': ['Africa','Africa','Africa','Africa','Africa','Africa','Africa','Africa','Asia','Asia','Asia','Asia'],
         'Country': ['South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','South Africa','Japan','Japan','Japan','Japan'],
         'Product': ['ABC','ABC','ABC','ABC','XYZ','XYZ','XYZ','XYZ','DEF','DEF','DEF','DEF'],
         'Year': [2016, 2017, 2018, 2019,2016, 2017, 2018, 2019,2016, 2017, 2018, 2019],
         'Price': [200, 100, 30,750,350,120,0,890,400,370,0,415]}

df3 = pd.DataFrame(data3)

有什么建议吗？