Pandas equivalent of SQL's row_number()

row_num.py

# Let's add an row number to indicate the first message per app & microservice
# This code is analagous to the SQL: row_number() over (partition by id, topic order by msg_ts asc)
df['row_num'] = df.sort_values(['id', 'msg_ts'], ascending=True).groupby(['id', 'topic']).cumcount() + 1

now i want to select all the rows in each group that has row_num=1

now i want to select all the rows in each group that has row_num=1

df[df.row_num == 1]

Thanks it worked

Thank you.