Question

So, I’m creating two random word generators, one based on bigrams and the other based on trigrams. In each case I’ve set up a dictionary (either called bigrams, which has two nested dictionaries or trigrams, which has three nested dictionaries)…and there is a lot of other code but here’s the line that causes a problem in the trigram generator:

 #generates random phonemes
 def generate_trigramphoneme(phoneme1, phoneme2):
    rand = random.uniform(0,1)

    **for phoneme3 in trigrams[phoneme1][phoneme2]:**
        rand -= trigrams[phoneme1][phoneme2][phoneme3]

        if rand < 0.0: return phoneme3
    return phoneme3

where the variable “phoneme3” produces a local unbound error.

Here, though, in my bigram generator (which works), the variable “Following” is fine, and doesn’t produce an error:

def generate_bigramphoneme(phoneme):
    rand = random.uniform(0,1)
    for following in bigrams[phoneme]:
        rand -= bigrams[phoneme][following]
        if rand < 0.0: return following
    return following

I looked up unbound local errors in python on eli bendersky’s website, which helped me understand the error, but I still don’t know how to get rid of it, or why the bigram code doesn’t produce an error…

Answer 1

Assuming you do have a trigrams defined somewhere, it may be that with your arguments, trigrams[phoneme1][phoneme2] is an empty iterable, therefore the loop never executes and phoneme3 doesn’t get bound.