diy.py

with open(r'C:\Users\Administrator\Documents\lesson13-1\sales_list.txt','r',encoding='utf-8') as file:
    a=file.readlines()
    f_sum=[]
for i in a:
    data=i.split()
    sum=0
    for sales in data[1:]:
        sum=sum+int(sales)
    r=str(sum)+data[0]+'\n'
    f_sum.append(r)
    print(r)
with open(r'C:\Users\Administrator\Documents\lesson13-1\sales_list.txt','w',encoding='utf-8') as file:
    file.writelines(f_sum)