Extract rows between two specific cells pandas

问题

I need to extract n rows between the cells epic and story from the column col2.

This is my input:

import pandas as pd
df = pd.DataFrame({'col1': ['aze ', 'az a', 'az a', 'azs abv','aze ', 'az a', 'azs abv', 'abc 45','wqas', 'foo bar abc', 'foo abv', 'abc 45', 'abc 45'], 'col2': ['epic', 'ac4', 'ac5', 'story','story', 'ac10', 'ac6', 'epic','ac11', 'ac1', 'ac2', 'ac3', 'story'], 'col3': ['hey', 'hello', 'hola', 'yoopy','hawdi', 'yiiha', 'yow', 'yalla', 'yiiha', 'yow', 'yalla', 'yalla', 'yalla']})  
print(df) 

           col1   col2   col3
0          aze    epic    hey
1          az a    ac4  hello
2          az a    ac5   hola
3       azs abv  story  yoopy
4          aze   story  hawdi
5          az a   ac10  yiiha
6       azs abv    ac6    yow
7        abc 45   epic  yalla
8          wqas   ac11  yiiha
9   foo bar abc    ac1    yow
10      foo abv    ac2  yalla
11       abc 45    ac3  yalla
12       abc 45  story  yalla

and this is the desired output :

          col1    col2    col3
0         az a     ac4    hello
1         az a     ac5    hola
2         wqas     ac11   yiiha
3   foo bar abc    ac1    yow
4       foo abv    ac2    yalla
5        abc 45    ac3    yalla

the solution proposed by @ansev gave me this output instead:

       col1   col2   col3
0     az a    ac4  hello
1     az a    ac5   hola
2     aze   story  hawdi
3     az a   ac10  yiiha
4  azs abv    ac6    yow
5   abc 45  story  yalla

回答1:

IIUC,boolean indexing with Series.mod to detect the change from epic to story after setting all values to False before the first epic.

epic = df['col2'].eq('epic') 
story = df['col2'].eq('story')
df.loc[(epic | story).where(epic.cumsum().ge(1), False)
                     .cumsum()
                     .mod(2)
                     .eq(1)
                     .where(~epic, False)].reset_index(drop=True)

Output

      col1 col2   col3
0     az a   ac  hello
1  azs abv   ac   hola

来源：https://stackoverflow.com/questions/61274014/extract-rows-between-two-specific-cells-pandas

标签

python-3.x

pandas

extract

rows