import csv
from decimal import Decimal as D
from datetime import datetime

DataPath = 'C:\\Users\\HP\\Downloads\\Triangle'
rows, cols = (15,15)
clm_trg = [[0 for i in range(cols)] for j in range(rows)]
calc_yr = 2021
calc_mth = 3

with open(DataPath + '\\Data_Triangle.txt', 'r') as file:
    DataReader = csv.reader(file, delimiter="\t")

    for Item in DataReader:
        loss_date = datetime.strptime(Item[1], '%d/%m/%Y').date()
        loss_yr = loss_date.year
        loss_mth = loss_date.month

        rpt_date = datetime.strptime(Item[2], '%d/%m/%Y').date()
        rpt_yr = rpt_date.year
        rpt_mth = rpt_date.month

        clm_amt = D(Item[3])

        clmmth = (calc_yr - loss_yr) * 12 + (calc_mth - loss_mth)
        devmth = (rpt_yr - loss_yr) * 12 + (rpt_mth - loss_mth)

        clm_trg[clmmth][devmth] = clm_trg[clmmth][devmth] + clm_amt

with open(DataPath + '\\TResult.txt', 'w', newline='\n') as res_file:
    DataWriter = csv.writer(res_file, delimiter='\t')

    for i in reversed(range(rows)):
        DataWriter.writerow(clm_trg[i])