def crossover(population):
"""
Performs crossover on a given generation of poems, swapping the first
and second halves of each poem in a generation
population (list): A list representing the breeding pool for the
current generation
"""
new_population = []
for i in range(0, len(population), 2):
new_poem1 = Poem()
new_poem1.first_half = population[i].first_half
new_poem1.second_half = population[i + 1].second_half
new_poem2 = Poem()
new_poem2.first_half = population[i + 1].first_half
new_poem2.second_half = population[i].second_half
new_population.append(new_poem1)
new_population.append(new_poem2)
return new_population
def seed_population(my_word, first_words):
"""
Generates a starting population of poems, using n-grams to generate
a word based on a previous sequence of words
my_word ()
first_words (string): a string representing the first n words of
the inspiring test, which are used to start the poem generation
"""
poem_string = first_words
old_sequence = first_words
population = []
# generates 20 poems for a generation
counter = 0
max_poems = 20
while counter < max_poems:
poem = Poem()
# each poem is 50 words
for i in range(50):
if len(poem_string) == 0:
random_word = old_sequence.split()[0]
else:
random_word = rand.choice(poem_string.split())
new_word = my_word.get_next_word(old_sequence, random_word) + " "
poem_string += new_word
line_val = i % 10
if line_val == 0:
poem_string += '\n'
# for the purposes of crossbreeding, splits the poem in half
if len(poem_string.split()) == 25:
if i > 25:
poem.second_half = poem_string
poem_string = ""
else:
poem.first_half = poem_string
poem_string = ""
old_word_list = old_sequence.split()
old_sequence = ""
for k in range(1, len(old_word_list)):
old_sequence = old_sequence + old_word_list[k] + " "
old_sequence = old_sequence + new_word
population.append(poem)
counter += 1
return population
def mutate(poem, word_dictionary, n_value, mutation_prob=0.05):
"""
Handles the mutation functions of the poem by calling helper functions
poem(Poem): the given poem to mutate
word_dictionary (word_dictionary): the dictionary containing the
n-grams information
n_value (int): the user inputted n value
mutation_prob (float): the probability that an indivudal word would be
mutated
"""
new_poem = Poem()
new_poem.first_half = get_words(poem.first_half, word_dictionary, n_value,
mutation_prob)
new_poem.second_half = get_words(poem.second_half, word_dictionary,
n_value, mutation_prob)
return new_poem
