更新给定索引的列值 pandas

Question

即使没有错误，也无法更新给定索引的数据帧的列值？

import pandas as pd

dict = {'col_1': {0: 'A', 1: 'B', 2: 'C'},
         'col_2': {0: 'I', 1: 'J', 2: 'K'},
         }
df = pd.DataFrame(dict)
my_index = [1,2]
df['col_3'] = None
df.loc[my_index, :].col_3 = 'X'

电流输出 (df)

  col_1  col_2  col_3
0   A     I     None
1   B     J     None
2   C     K     None

预期输出 (df)

  col_1  col_2  col_3
0   A     I     None
1   B     J     X
2   C     K     X

Answer 1

让我们试试

df.loc[my_index, 'col_3'] = 'X'
df
Out[14]: 
  col_1 col_2 col_3
0     A     I  None
1     B     J     X
2     C     K     X