Add group number for duplicates

[atomxkai]

Hi, looking how to add sequence and group them by numbers for duplicates.

index raw count group number filename Number of Pages CRITERIA
0 1 1 1 file_753951.pdf 2 Starwars
3 4 2 1 file_654321.pdf 2 Starwars
4 5 3 1 file_456123.pdf 2 Starwars
5 6 4 1 file_548564.pdf 2 Starwars
11 12 5 2 file_351643.pdf 2 Trekky
13 14 6 2 file_789654.pdf 2 Trekky
2 3 7 3 file_321564.pdf 2 Guardians
15 16 8 3 file_963852.pdf 2 Guardians
12 13 9 3 file_741852.pdf 3 Guardians

mydata = df["Criteria"]
df_getdupes = df[cfc.isin(cfc[cfc.duplicated()])].sort_values(['Criteria','Number of Pages'])
display(df_getdupes)
df_getdupes.to_csv('output_dupes1.csv')

Updates:
Dec 8
1. the screenshot is my required output.

problem:
1. create group number field
2. write sequential number in group number field per criteria. should be same group number per criteria.

Thank you.