python - 当单词不在句子中时无法让程序打印 "not in sentence"

Question

我有一个程序要求输入一个句子，然后要求输入一个词，并告诉你那个词的位置:

sentence = input("enter sentence: ").lower()
askedword = input("enter word to locate position: ").lower()
words = sentence.split(" ")

for i, word in enumerate(words):
     if askedword == word :
          print(i+1)
    #elif keyword != words :
         #print ("this not")

但是，当我编辑程序时，如果输入的单词不在句子中，则打印“this isn't in the sentence”，我无法让程序正常工作

Answer 1

列表是序列，因此您可以使用 the in operation在它们上测试 words 列表中的成员资格。如果在里面，用words.index找到句子里面的位置:

sentence = input("enter sentence: ").lower()
askedword = input("enter word to locate position: ").lower()
words = sentence.split(" ")

if askedword in words:
    print('Position of word: ', words.index(askedword))
else:
    print("Word is not in the given sentence.")

带有示例输入:

enter sentence: hello world

enter word to locate position: world
Position of word: 1

并且，一个错误的案例:

enter sentence: hello world

enter word to locate position: worldz
Word is not in the given sentence.

如果您要检查多个匹配项，那么使用 enumerate 的列表理解是可行的方法:

r = [i for i, j in enumerate(words, start=1) if j == askedword]

然后检查列表是否为空并相应地打印:

if r:
    print("Positions of word:", *r)
else:
    print("Word is not in the given sentence.")