One of my current projects is the Daily Programmer challenge here.  It’s a project to write a program to play a version of a hacking minigame from the Fallout series.  Here, I’ll work through my design process for a Python 3.4 implementation.

I started by just throwing out a little bit of code.  I didn’t expect this to get me anywhere, at least nowhere good.  But sometimes, just typing a few things out can help you realize what a project requires that purely thinking through it doesn’t.

I quickly realized I needed a data structure of some sort to hold the list of potential words.  A simple list of words would work, but depending on my source wordlist, I might end up with many words longer and shorter than the 4-15 letters the game design specifies.  I’d also have to look through the entire list to retrieve the small handful of words that are part of a run of the game.  Simply using a list would mean I’d have to account for these issues in many places in the game code, and that’s a problem.

I could use a list, and then have functions I call to work with the list.  But then I’d have to worry about global variables and/or passing a list all over the place.  That can be quite a mess.  Not as bad as repeating my data access code, but still a mess.  So I decided to implement it as a class, to package the data and its access code together.

I decided first it needed a way to give the user a list of words of appropriate length.  From here, I tried to think of an appropriate internal representation, and the easiest seemed to be a list of lists, indexed by word length. With that, I can use random.sample() to easily get an appropriate length list.

I can also use a function to fill the internal data structure that rejects words with lengths outside the specified limits.  There’s no sense having words with length of 16 in the data structure when I never need words that long.

The complete class is as follows:

class HackingGameWordList: 
    def __init__(self, wordlist):
    """ Wordlist is a list of strings, constants determine
    what length words I want to pull from the list
    """
 
        self._MIN_LENGTH = 4
        self._MAX_LENGTH = 15
        self.words = [[] for _ in range(self._MAX_LENGTH)]
        self.fill_list(wordlist)
 
    def fill_list(self, wordlist):
        """ Breaks up the full wordlist into the internal list of lists
        indexed by word length
        """
        for word in wordlist:
            l = len(word)
            if l >= self._MIN_LENGTH and l <= self._MAX_LENGTH:
                self.words[l].append(word)
 
     def get_n_words(self, n, l):
         """ Return a list of n randomly selected words of length l """
         return random.sample(self.words[l], n)