python - 添加来自两个不同数据帧的两列，所有其他列都相同

Question

如何从两个不同的 DataFrame 添加两列，其中除了我想要添加的列之外，所有列都相等？

请参阅下面的示例代码:

#IN:
import pandas as pd
import numpy as np
#Observe that 'col2' in both dataframes are equal
df1 = pd.DataFrame({'col1': [3.2, 4.4, 6.5, np.NaN], 'col2': [1.2, 2.2, np.NaN, 5.7]})

     col1    col2
0    3.2     1.2
1    4.4     2.2
2    6.5     nan
3    nan     5.7

df2 = pd.DataFrame({'col1': [1.0, 2.0, 3.0, 4.0], 'col2': [1.2, 2.2, np.NaN, 5.7]})

     col1    col2
0    1.0     1.2
1    2.0     2.2
2    3.0     nan
3    4.0     5.7

# new_df = [INSERT SOME MAGIC FUNCTION HERE]
# I tried: new_df = df1.add(df2, level='col1')    
# but obviously that did not work

#OUT (This is what I want):
print(new_df)

     col1   col2
0    4.2    1.2
1    6.4    2.2
2    9.5    nan
3    4.0    5.7

观察np.NaN + some_float = some_float

Answer 1

这是一种方法。添加 2 个系列时请记住 fillna(0)。

res = pd.DataFrame({'col1': df1['col1'].fillna(0) + df2['col1'].fillna(0),
                    'col2': df1['col2']})

print(res)

#    col1  col2
# 0   4.2   1.2
# 1   6.4   2.2
# 2   9.5   NaN
# 3   4.0   5.7