Pandas在一定条件下繁殖

Question

当前Df为：

XXXX    apples  -1000000    Bob
XXXX    oranges -1000000    Sam
AAAA    apples  -2400000    Bob
XXXX    pears   1000000 Bob
XXXX    pears   1000000 Sam
XXXX    grapes  1000000 Bob
AAAA    grapes  1000000 Bob
XXXX    apples  1200000 Bob
AAAA    apples  1900000 Sam
XXXX    grapes  -1100000    Sam

如果第一列等于'XXXX'，第四列等于'Bob'，我想将第三列中的QUNTITY乘以-1

我尝试过在条件下使用loc和过滤，但似乎无法正确实现

Answer 1

在适当的位置执行并维护语法-

df['col_3'] = df.where((df['col_1'] == 'XXXX') & (df['col_4'] == 'Bob'))['col_3'] * -1

Answer 2

您可以使用^{}：

df['col_3'] = np.where((df['col_1']=='XXXX') & (df['col_4']=='Bob'), -1*df['col_3'], df['col_3'])

收益率：

  col_1    col_2    col_3 col_4
0  XXXX   apples  1000000   Bob
1  XXXX  oranges -1000000   Sam
2  AAAA   apples -2400000   Bob
3  XXXX    pears -1000000   Bob
4  XXXX    pears  1000000   Sam
5  XXXX   grapes -1000000   Bob
6  AAAA   grapes  1000000   Bob
7  XXXX   apples -1200000   Bob
8  AAAA   apples  1900000   Sam
9  XXXX   grapes -1100000   Sam