Select all 5 letters words

output_file = open("output1.txt", "w")

with open("words_466000.txt", "r") as input_file:
    words_count = 0.
    iter_counter = 0.
    not_alpha = 0
    for text_line in input_file:
        if iter_counter >= 10**8:
            break
        else:
            iter_counter += 1
            if len(text_line) == 6: #12345\n
                if text_line[:-1].isalpha(): #12345
                    words_count += 1
                    output_file.write(text_line.lower() + '\n')
print "words_count: ", words_count
print "iter_counter: ", iter_counter
print "percent of all words: ", words_count / iter_counter