根据其他列的唯一值重命名列值

Question

给出一个数据框：

df = 

  id_easy   ordinal   weekday
0       0         1   Tuesday
1       0         2   Monday
2       0         3   Monday
3       1         1   Saturday
4       1         2   Tuesday

我要检查：

• 在每个id_easy唯一值中，当weekday为ordinal时，将1列重命名为其值。

所需的输出：

df = 

  id_easy   ordinal   weekday
0       0         1   Tuesday       # as this is Tuesday
1       0         2   Tuesday       # so this became Tuesday as well
2       0         3   Tuesday       # so this became Tuesday as well
3       1         1   Saturday      # as this is Saturday
4       1         2   Saturday      # so this became Saturday as well

Answer 1

您可以使用groupby：

df.weekday = df.groupby('id_easy')['weekday'].transform('first') 

输出：

   id_easy  ordinal   weekday
0        0        1   Tuesday
1        0        2   Tuesday
2        0        3   Tuesday
3        1        1  Saturday
4        1        2  Saturday