pandas如何根据一行数据，添加对应的行数据

请教大神，如何用pandas实现图片中的效果

以下是input.csv

金额,起息日,到期日,占款天数
100,2019-06-28,2019-07-01,3
300,2019-06-28,2019-07-01,2
600,2019-06-19,2019-06-20,1
123,2019-05-08,2019-05-10,2

正文开始

import pandas as pd
import datetime
csv_data = pd.read_csv("input.csv")

newhead=['金额','起息日','到期日']
newdf=pd.DataFrame(columns=newhead) #新建一个df
k=0 #索引起始计数
for i in csv_data.index:
    days=csv_data.loc[i,'占款天数']
    currday=csv_data.loc[i,'起息日']
    currdaytodatetime=datetime.datetime.strptime(currday,'%Y-%m-%d')
    money=csv_data.loc[i,'金额']
    terday=csv_data.loc[i,'到期日']
    for day in range(int(days)):
        newrow=[money,currday,terday]
        newdf.loc[k]=newrow
        currdaytodatetime+=datetime.timedelta(days=1)#日期加1 
        currday=currdaytodatetime.strftime('%Y-%m-%d')
        k+=1
newdf.to_csv('out.csv',index=False)