Python 3 задача с текстовыми файлами

z = 0
itog = 0
string = ''
with open('C:\\Users\\user1\\Desktop\\shop_1.txt', 'r', encoding='utf-8') as f:
    line = f.readline()
    for i in line:
        if line.isalpha():
            new = line[i]
        else:
            summa = line[i].split(' ')
            znach = int(summa[0]) * summa[1]
            itog += znach
    string += (new + ' ' + str(z) + '\n')
with open('C:\\Users\\user1l\\Desktop\\form.txt', 'w') as f1:
    f1.write(string + str(itog))
f.close()
f1.close()

string=''
znach=0
itog=0
with open('C:\\Users\\user1\\Desktop\\shop_1.txt', 'r', encoding='utf-8') as f:
    line = str(f.read()).split('\n')
    for i in range(len(line)):
        if i % 2 == 0:
            new = line[i]
        else:
            summa = line[i].split(' ')
            znach = int(summa[0]) * int(summa[1])
            itog += znach
    string += (new + ' ' + str(znach) + '\n')   #ValueError: invalid literal for int() with base 10: '12.6'
with open('C:\\Users\\user1\\Desktop\\form.txt', 'w') as f1:
    f1.write(string + str(itog))
f.close()
f1.close()