[redhead]

Works for me:

#!/usr/bin/python
import re             
returnline = []
f = open("List", "r") 
for line in f.readlines(): 
    returnline.append(re.compile(' ').sub(',', line[0:-1]))
for item in returnline:
    print item

> ./test.py
------------------------------------------
12400,,JOHN,,MAN,,IT,
------------------------------------------
12500,,NICE,,JOHN,,LAW,
-------------------------------------------
12600,,PATRICK,,MAN,,CS,
------------------------------------------