import pandas as pd 
from datetime import timedelta
nowcoder=pd.read_csv('nowcoder.csv',sep=',')
#日期转换
nowcoder['date']=pd.to_datetime(nowcoder.date).dt.date
#去重
nowcoder=nowcoder.drop_duplicates(subset=['user_id','date'])
#复制，日期加一
nowcoder2=nowcoder.copy()
nowcoder2['date']=nowcoder2['date']+timedelta(1)
#留存数
num_re=pd.merge(nowcoder,nowcoder2,on=['user_id','date']).shape[0]
#总计数
num_total=nowcoder.shape[0]
#留存率
print(round(num_re/num_total,2))