《Python编程快速上手——让繁琐工作自动化》作业-4.10.1 逗号代码

spam = ['apples', 'bananas', 'tofu', 'cats']

spam = []
while True:
    print ('Enter some words into spam:')
    spam_input = input()
    if spam_input == '':
        break
    spam = spam + [spam_input]
def add_and(spam):
    spam_and = 'and ' + spam[-1]
    del spam[-1]
    spam.append(spam_and)
    spam0 = spam[0]
    for i in range(len(spam) - 2):
        spam0 = spam0 + ',' + spam[i + 1]
    spam_all = spam0 + ',' + spam[-1]
    print (spam_all)
    
add_and(spam)