longest-word.py

"""A script to find the longest word with all letters in alphabetical order."""

import sys
import string

DICTIONARY = "/usr/share/dict/british-english"
LETTERS = string.lowercase

def len_letters(word):
    """Return the length of a word counting only its letters.

    >>> len_letters("graham's")
    7
    """
    return len([char for char in word if char in LETTERS])


def find_longest_ordered_word(words):
    """Find and return the longest word in `words` whose letters are ordered.

    :param words: A list of words.
    :return: The longest word in `words` whose letters are ordered
             alphabetically.

    >>> find_longest_ordered_word(["alphabet", "almost"])
    'almost'
    """
    ordered_words = set()

    for word in words:
        word = word.lower().strip()
        if word.endswith("'s"):
            continue

        last_char_index = None
        is_ordered = True
        for character in word:
            if character not in LETTERS:
                # Discard any non A-Z characters.
                continue
            if LETTERS.index(character) > last_char_index:
                last_char_index = LETTERS.index(character)
            else:
                is_ordered = False
        if is_ordered:
            ordered_words.add(word)

    longest_ordered_word = ""
    longest_ordered_words = set()
    for ordered_word in ordered_words:
        if len_letters(ordered_word) == len_letters(longest_ordered_word):
            longest_ordered_words.add(ordered_word)
        elif len_letters(ordered_word) > len_letters(longest_ordered_word):
            longest_ordered_word = ordered_word
            longest_ordered_words = set()
            longest_ordered_words.add(ordered_word)

    if len(longest_ordered_words) == 1:
        return (longest_ordered_word, 1)
    else:
        return (
            ", ".join(
                "{0} ({1})".format(word, len_letters(word))
                for word in sorted(longest_ordered_words)),
            len(longest_ordered_words))


if __name__ == "__main__":
    with open(DICTIONARY, "r") as dictionary_file:
        words = dictionary_file.readlines()

    if "--reverse" in sys.argv:
        # Reverse the LETTERS list so that 'z' is at the start of the
        # alphabet and so on.
        LETTERS = LETTERS[::-1]
    words, count = find_longest_ordered_word(words)
    print("Found {0} longest ordered words:".format(count))
    print(words)