使用python3.5用其他行值减去一列的行？

import pandas as pd

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

df['D'] = df['A'] - df['B']

import pandas as pd

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

df['D'] = df['A'] - df['B']

print(df)

   A  B   C  D
0  1  5   9 -4
1  2  6  10 -4
2  3  7  11 -4
3  4  8  12 -4