为什么我按照书上的运行一直显示这个

Question

def break_words(stuff): """This function will break up words for us.""" words = stuff.split(' ') return words def sort_words(words): """Sorts the words.""" return sorted(words) def print_first_word(words): """Prints the first word after popping it off.""" word = word.pop(-1) print word def print_last_word(words): """Prints the last word after popping it off .""" word = wor.pop(-1) print word def sort_sentence(sentence): """Prints in a full sentence and return the sorted words.""" words = break_words(sentence) return sort_words(word) def print_first_and_last(sentence): """Prints the first and last words of the sentence.""" words = break_words(sentence) print_first_word(words) print_last_word(words) def print_first_and_last_sorted(sentence): """Sorts the words then prints the first and last one.""" words = sort_sentence(sentence) print_first_word(words) print_last_word(words)

Answer 1

注意import