import pandas as pd
df = pd.DataFrame({'A':'foo foo foo bar bar bar'.split(),
'B':[0.1, 0.5, 1.0]*2})
df['C'] = df.groupby(['A'])['B'].transform(
lambda x: pd.qcut(x, 3, labels=range(1,4)))
print(df)
yields
A B C
0 foo 0.1 1
1 foo 0.5 2
2 foo 1.0 3
3 bar 0.1 1
4 bar 0.5 2
5 bar 1.0 3