更多更多的练习

• 输入：

# -*- coding: utf-8 -*-

def break_words(stuff):
    """This function will break up words for us."""
    words = stuff.split(' ')
    #Python split()通过指定分隔符对字符串进行切片，
    #如果参数num 有指定值，则仅分隔 num 个子字符串。
    return words

def sort_words(words):
    """Sorts the words."""
    return sorted(words)
    #sorted是一种排序功能，这里是讲words的内容进行排序

def print_first_word(words):
    """Prints the first word after popping it off."""
    word = words.pop(0)
    #pop() 函数用于移除列表中的一个元素（默认最后一个元素），
    #并且返回该元素的值。这里的0代表第一个元素
    print word

def print_last_word(words):
    """Prints the last word after popping it off."""
    word = words.pop(-1) #移除最后一个元素，并返回该元素的值
    print word

def sort_sentence(sentence):
    """Takes in a full sentence and returns the sorted words."""
    words = break_words(sentence)
    #将上面已经移除第一个元素和最后一个元素的值赋予words
    return sort_words(words)

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)

-运行：

这段眼花缭乱的代码，试了好几次才完全输入正确并运行成功。。。