Пользовательская сессия из анализ бизнес-показателей

import pandas as pd
from matplotlib import pyplot as plt

sessions = pd.read_csv('users_sessions_data.csv')
sessions['session_start_ts'] = pd.to_datetime(sessions['session_start_ts'])

# определяем год и месяц начала сессии
sessions['session_year'] = sessions['session_start_ts'].dt.year
sessions['session_month'] = sessions['session_start_ts'].dt.month

sessions_per_user = sessions.groupby(['session_year', 'session_month']).agg(
{'client_id':['count', 'nunique']})

sessions_per_user.columns = ['n_sessions', 'n_users']

sessions_per_user['sess_per_user'] = (
    sessions_per_user['n_sessions']/ sessions_per_user['n_users'])

print(sessions_per_user)