recovery the csv file destroy by microsoft excel

recovery.py

# scrip to recovery a csv file ruined by Excel
# usage python recovery.py [filename.csv]
import re
import sys

def recovery(line, n_f_lines):
    n_line = re.sub(r"\n", "ENTER", line)
    n_line = re.sub(r"\s+", ",", n_line)
    n_line = re.sub("ENTER", "\n", n_line)
    n_f_lines.append(n_line)


def main():
    file_name = sys.argv[1]
    csv_suff = ".csv"
    if(not file_name.endswith(csv_suff)):
        print("This file is not a valid csv file")
        exit()
    f = open(file_name, "r")
    n_f = open(file_name + ".output", "w+")
    n_f_lines = []
    for line in f:
        recovery(line, n_f_lines)
    n_f.writelines(n_f_lines)
    f.close()
    n_f.close()
        
    

if __name__ == "__main__":
    main()