如何整合 RI 续购日期

import pandas as pd
from datetime import *
from datetime import date
from datetime import datetime

table = pd.read_excel("blog5_output.xlsx")
start_day = min(table['ri_expired_date']).date()
end_day = max(table['ri_expired_date']).date()
duration = (end_day - start_day).days
total_item = table.shape[0]
cost = []
for x in range(0, duration + 1):
    sub_total = 0
    for i in range(0, total_item):
        current_item_date = (table.loc[[i]].ri_expired_date)[i].date()
        # old price duration
        op_day = ((current_item_date - start_day).days) - x
        # on demand price duration
        od_day = x - ((current_item_date - start_day).days)
        # new price duration
        np_day = (duration - x)
        if op_day < 0:
            op_day = 0
        if od_day < 0:
            od_day = 0
        sub_total += ((table.loc[[i]].source_price)[i] / 365 * op_day + (table.loc[[i]].target_price)[i] / 365 * np_day + (table.loc[[i]].source_ondemand) * od_day * 24)[i]
    cost.append(sub_total)
optimize_cost = min(cost)

print("{}   {}".format('    Date', '    Cost'))
for i in range(0, len(cost)):
    if cost[i] == optimize_cost:
        recommand_date = start_day + timedelta(days=i)
    current_date = start_day + timedelta(days=i)
    current_date = datetime.combine(current_date, datetime.min.time())
    print("{}   {:.2f}".format(current_date.strftime('%Y-%m-%d'), cost[i]))
print ('\nRecommanded date to buy RI is {}'.format(recommand_date)) 

$ python ri_plan.py    Date       Cost2019-05-21   135170.432019-05-22   129999.902019-05-23   124917.962019-05-24   119982.302019-05-25   115046.642019-05-26   110110.982019-05-27   105175.322019-05-28   100239.652019-05-29   102823.482019-05-30   105407.302019-05-31   107991.122019-06-01   110574.952019-06-02   113158.772019-06-03   115742.592019-06-04   118326.422019-06-05   127722.572019-06-06   137703.242019-06-07   147683.912019-06-08   157664.582019-06-09   167645.262019-06-10   177625.932019-06-11   187606.602019-06-12   197587.27 Recommended date to buy RI is 2019-05-28