如何重塑数据帧，使前两列形成新列的名称，该新列从另一列获取值？

import pandas as pd

data = {'Column1': [1, 2, 3, 4],
        'Column2': [5, 6, 7, 8],
        'Column3': [9, 10, 11, 12]}
df = pd.DataFrame(data)

df['NewColumn'] = df['Column1'].astype(str) + '_' + df['Column2'].astype(str)

print(df)

   Column1  Column2  Column3 NewColumn
0        1        5        9       1_5
1        2        6       10       2_6
2        3        7       11       3_7
3        4        8       12       4_8