from sys import argv
import os
if len(argv) < 3:
    print("Usage:  python copy.py donor recipient")
    quit()
donor = argv[1]
recipient = argv[2]
if not os.path.exists(donor):
    print("You are attempting to copy from a nonexistent file.")
    quit()
    
with open(donor, "r") as fp_in:
    with open(recipient, "w") as fp_out:
        for line in fp_in:
            fp_out.write(line)


##  copy file donor to recipient
##  open the donor to read it.
##  open the recipient for writing
##  copy each line from the donor to the recipient
##  ensure both files are closed at the end.