python数据帧按行与条件求和

Question

两个数据帧，我想按行分组，列a和b。我想在b列中对所有'x'和'z'的行求和，并将其称为'v'。

import pandas as pd


df = pd.DataFrame({'a': ['day1','day1','day1','day2','day2','day2'], 'b': ['x','z','y','x','z','y'], 'c':[9,1,6,0,5,6], 'd':[6,9,1,3,5,9]})

结果应为：

df2 = pd.DataFrame({'a': ['day1','day1','day2','day2'], 'b': ['v','y','v','y'], 'c':[10,6,5,6], 'd':[15,1,8,9]})

Answer 1

In [106]: df.replace({'b':{'x':'v','z':'v'}}).groupby(['a','b'], as_index=False).sum()
Out[106]:
      a  b   c   d
0  day1  v  10  15
1  day1  y   6   1
2  day2  v   5   8
3  day2  y   6   9

或

In [114]: to_replace=['x','z']

In [115]: replace_with=['v','v']

In [116]: df.assign(b=df.b.replace(to_replace, replace_with)).groupby(['a','b'], as_index=False).sum()
Out[116]:
      a  b   c   d
0  day1  v  10  15
1  day1  y   6   1
2  day2  v   5   8
3  day2  y   6   9