B
Size: a a a
B
B
CJ
CJ
B
CJ
B
CJ
I

B
B
CJ
YK
df = pd.DataFrame([['ы','b','b','b'],
['э',1, 2, 3],
['б',2,2,4],
['ю','s','s','s'],
['я',1,2,3],
['ф',2,5,4]])
sub_groups = ['b', 's']
df.iloc[df[df.iloc[:,1]==sub_groups[0]].index.values.astype(int)[0] : df[df.iloc[:,1]==sub_groups[1]].index.values.astype(int)[0]]
БГ
БГ
БГ
БГ
БГ
line.strip()I

YD