从您的表中，我只能推断出您希望基于Follow up month中的相应值创建Timepoint列，该列看起来如下所示：

from io import StringIO
import pandas as pd
wt = StringIO("""ID  Follow up month  Value-x  value -y
1  0  12  12
1  0  11  14
2  0  10  11
2  3  11  0
2  0  12  1
1  3  13  12
2  3  11  5""")

df = pd.read_csv(wt, sep='\s\s+')
df['Timepoint'] = df['Follow up month'].apply(lambda x: 1 if x==0 else 2)
df

输出：

ID  Follow up month  Value-x  value -y  Timepoint
0   1                0       12        12          1
1   1                0       11        14          1
2   2                0       10        11          1
3   2                3       11         0          2
4   2                0       12         1          1
5   1                3       13        12          2
6   2                3       11         5          2

编辑

根据您的评论，这应该是您想要的：

def timepoint(s):
    if not s.isin([0]).any() and s.iloc[0] == 3:
        return 1
    else:
        return s.apply(lambda x: 1 if x==0 else 2)

df['Timepoint'] = df.groupby('ID')['Follow up month'].transform(timepoint)