Python 将运行索引添加到按用户id分区的索引

鉴于此数据集

CUSTOMER_ID,ORDER_AT
A,2020-11-11 23:30:13
A,2020-11-11 23:32:53
A,2020-11-11 23:34:44
A,2020-11-11 23:35:55
B,2020-11-11 23:37:54
B,2020-11-11 23:39:23
C,2020-11-09 23:59:46
C,2020-11-10 0:03:04
C,2020-11-10 0:05:35
C,2020-11-10 0:19:40
C,2020-11-11 2:48:17
C,2020-11-11 2:49:06
C,2020-11-11 2:50:39
C,2020-11-11 2:51:57
D,2020-11-14 1:12:52
D,2020-11-14 1:13:14
D,2020-11-14 16:56:18

如何创建由客户id分区的事务id的运行辅助索引

我期望的输出是

CUSTOMER_ID,CUSTOMER_TRANSACTION_ID,ORDER_AT
A,0,2020-11-11 23:30:13
A,1,2020-11-11 23:32:53
A,2,2020-11-11 23:34:44
A,3,2020-11-11 23:35:55
B,0,2020-11-11 23:37:54
B,1,2020-11-11 23:39:23
C,0,2020-11-09 23:59:46
C,1,2020-11-10 0:03:04
C,2,2020-11-10 0:05:35
C,3,2020-11-10 0:19:40
C,4,2020-11-11 2:48:17
C,5,2020-11-11 2:49:06
C,6,2020-11-11 2:50:39
C,7,2020-11-11 2:51:57
D,0,2020-11-14 1:12:52
D,1,2020-11-14 1:13:14
D,2,2020-11-14 16:56:18

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尝试

Groupby

和

cumcount（）

我不确定你是否需要累计金额。累计金额足够（基于OP的输出）。你是对的@sammywemmy，将进行编辑。谢谢，谢谢！是的，累计金额足够了
df['CUSTOMER_TRANSACTION_ID']=df.groupby('CUSTOMER_ID').cumcount()