Convert free source form Fortran to lower case, except for comments

xlower_case_fortran.py

"""convert Fortran code to lower case except for comments
usage: python xlower_case_fortran.py <source_file>
The script writes lower case code to standard output.
"""
from sys import argv
source_file = argv[1] 
fp = open(source_file,"r")
for line in fp:
    text = line.rstrip()
    ipos = text.find("!")
    if ipos >= 0:
        print(text[:ipos].lower() + text[ipos:])
    else:
        print(text.lower())