# open the file in "write" mode
# (meaning if the file doesn't exist yet, create it)
out_file = open("countdown.txt", "w")

for i in range(10, 0, -1):
    # write() only takes strings, so we need to convert
    # our variable i into a string.
    # write also doesn't add line breaks, so we need to
    # include the newline character: "\n" ourselves
    out_file.write(str(i) + "\n")
out_file.write("Liftoff!")
out_file.close()