题解 | #牛客网用户练习的平均次日留存率#

import pandas as pd
a = pd.read_csv('nowcoder.csv', sep=',')
a['date'] = pd.to_datetime(a['date']).dt.date
a.drop_duplicates(subset=['user_id','date'],inplace=True)
b = a.copy()
b['date'] = b['date'] + pd.Timedelta(days=1)
c = pd.merge(a,b,on=['date','user_id'],how='inner',suffixes=('_a','_b'))
n1 = c['user_id'].count()
n2 = a['user_id'].count()
print(round(n1/n2,2))