"""
 make_words.py

 create words.txt from /usr/share/dict/words, leaving out
 (a) words with fewer than four letters, and
 (b) words with any characters other than lowercase a-z.

"""

import re   # regular expressions
lowercase = re.compile("[a-z]+")

def valid(word):
    return lowercase.fullmatch(word) and len(word) > 4

def main():
    from_file = open('/usr/share/dict/words', 'r')
    to_file = open('./words.txt', 'w')
    while True:
        word = from_file.readline().strip()
        if not word: return
        if valid(word): to_file.write(word + '\n')
        
main()