对具有相同条件的多列执行计算

Question

我有以下DataFrame:

df = pd.DataFrame([[1,2,3],
[-1,3,2],
[3,4,5],
[-3,4,5]], columns=['A','B','C'])
condition = df['A']>0
df.loc[condition, 'B'] = df['B'] + 1
df.loc[condition, 'C'] = df['C'] * 2
print(df.head())

我基于相同的条件对两个列执行两个不同的操作。将这两行代码组合成一行代码的最佳方法是什么?

df.loc[condition, 'B'] = df['B'] + 1
df.loc[condition, 'C'] = df['C'] * 2

Answer 1

两个Series使用concat，因为不同的操作:

df.loc[condition, ['B','C']] = pd.concat([df['B'] + 1, df['C'] * 2], axis=1)
print(df)
A  B   C
0  1  3   6
1 -1  3   2
2  3  5  10
3 -3  4   5

在我看来2行更可读:

df.loc[condition, 'B'] += 1
df.loc[condition, 'C'] *= 2

Answer 2

一个选项是assign:

df.assign(B = df.B.mask(condition, df.B + 1), 
C = df.C.mask(condition, df.C * 2))
Out[298]:
A  B   C
0  1  3   6
1 -1  3   2
2  3  5  10
3 -3  4   5