Doing calculation with ascii file

[snippsat]

Yes can do it like this.
Here an other version you can look at using f-string.
Also put in header line just as a example.
See that with string formatting(f-string) it look better no need for str() or +.

with open('col.txt') as f,open('total.txt', 'w') as f_out:
    header = next(f)
    c1, c2 = header.strip().split(',')
    f_out.write(f'{c1} {c2}  Sum\n')
    for line in f:
        line = line.strip()
        num1, num2 = line.split(',')
        num1, num2 = int(num1), int(num2)
        num3 = num1 + num2
        f_out.write(f'{num1} + {num2}  ${num3}\n')

Output:
colA colB  Sum
324 + 234  $558
346 + 341  $687
147 + 346  $493
234 + 567  $801
368 + 405  $773
344 + 643  $987
235 + 235  $470
236 + 567  $803