diy.py

with open(r'c:\Users\Lenovo\Desktop\sales_list.txt','r',encoding = 'utf-8') as file:
    data = file.readlines()
final = []
for i in data:
    newData = i.split()
    sum = 0
    for sales in newData[1:]:
        sum += int(sales)
    q = newData[0] + str(sum)+'\n'
    final.append(q)
with open(r'c:\Users\Lenovo\Desktop\sales_list.txt','r',encoding = 'utf-8') as file:
    file.writelines('\n')
    file.writeliens(final)