При запуске скрипта через IDLE создает только пустой текстовый файл. При запуске через консоль, наполняет файлы текстом. Почему так?

#!/usr/bin/env python3
# Copyright (c) 2008 Qtrac Ltd. All rights reserved.
# This program or module is free software: you can redistribute it and/or
# modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version. It is provided for educational
# purposes and is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.

import random


def get_forenames_and_surnames():
    forenames = []
    surnames = []
    for names, filename in ((forenames, "data/forenames.txt"),
                            (surnames, "data/surnames.txt")):
        for name in open(filename, encoding="utf8"):
            names.append(name.rstrip())
    return forenames, surnames


forenames, surnames = get_forenames_and_surnames()
fh = open("test-names1.txt", "w", encoding="utf8")
for i in range(100):
    line = "{0} {1}\n".format(random.choice(forenames),
                              random.choice(surnames))
    fh.write(line)