# 熊猫：如何根据其他列值的条件求和？

ShanZhengYang

``````import pandas as pd

print(df)

dog      A         B           C
0     dog1    0.787575  0.159330    0.053095
1     dog10   0.770698  0.169487    0.059815
2     dog11   0.792689  0.152043    0.055268
3     dog12   0.785066  0.160361    0.054573
4     dog13   0.795455  0.150464    0.054081
5     dog14   0.794873  0.150700    0.054426
..    ....
8     dog19   0.811585  0.140207    0.048208
9     dog2    0.797202  0.152033    0.050765
10    dog20   0.801607  0.145137    0.053256
11    dog21   0.792689  0.152043    0.055268
....
``````

``````df['total_ABC'] = df[["A", "B", "B"]].sum(axis=1)
``````

``````df['smallA_sum'] = df1.apply(lambda row: (row['A']+row['B']+row['C']) if row['A'] < 0.78))
``````

`````` df['dog2_sum'] = df1.apply(lambda row: (row['A']+row['B']+row['C']) if df['dog'] == 'dog2'))
``````

`

``````In [67]:
df = pd.DataFrame(np.random.randn(5,3), columns=list('ABC'))
df

Out[67]:
A         B         C
0  0.197334  0.707852 -0.443475
1 -1.063765 -0.914877  1.585882
2  0.899477  1.064308  1.426789
3 -0.556486 -0.150080 -0.149494
4 -0.035858  0.777523 -0.453747

In [73]:
df['total'] = df.loc[df['A'] > 0,['A','B']].sum(axis=1)
df['total'].fillna(0, inplace=True)
df

Out[73]:
A         B         C     total
0  0.197334  0.707852 -0.443475  0.905186
1 -1.063765 -0.914877  1.585882  0.000000
2  0.899477  1.064308  1.426789  1.963785
3 -0.556486 -0.150080 -0.149494  0.000000
4 -0.035858  0.777523 -0.453747  0.000000
``````

``````In [75]:
df['total'] = df[['A','B']].sum(axis=1).where(df['A'] > 0, 0)
df

Out[75]:
A         B         C     total
0  0.197334  0.707852 -0.443475  0.905186
1 -1.063765 -0.914877  1.585882  0.000000
2  0.899477  1.064308  1.426789  1.963785
3 -0.556486 -0.150080 -0.149494  0.000000
4 -0.035858  0.777523 -0.453747  0.000000
``````

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