diy.py

with open(r'c:\Users\Administrator\Desktop\sales_list.txt','r',encoding='utf-8') as lmc:
    a=lmc.readlines()
final_sum=[]
for i in a:
    data=i.split()
    sum=0
    for sales in data[1:]:
        sum=sum+int(sales)
        print()
    result=data[0]+str(sum)+'\n'
    final_sum.append(result)
with open(r'c:\Users\Administrator\Desktop\sales_list.txt','w',encoding='utf-8') as lmc:
    lmc.writelines(final_sum)
    lmc.close()