python 3.6 : Moving around words within a string

Question

我知道这个函数会围绕字符串中的字符移动，例如:

def swapping(a, b, c):
    x = list(a)
    x[b], x[c] = x[c], x[b]
    return ''.join(x)

这让我可以这样做:

swapping('abcde', 1, 3)
'adcbe'
swapping('abcde', 0, 1)
'bacde'

但是我怎样才能让它做这样的事情，所以我不只是四处移动字母？这就是我想要完成的:

swapping("Boys and girls left the school.", "boys", "girls")
swapping("Boys and girls left the school.", "GIRLS", "bOYS")
should both have an output: "GIRLS and BOYS left the school." 
# Basically swapping the words that are typed out after writing down a string

Answer 1

你可以这样做:

def swap(word_string, word1, word2):
    words = word_string.split()
    try:
        idx1 = words.index(word1)
        idx2 = words.index(word2)
        words[idx1], words[idx2] = words[idx2],words[idx1]
    except ValueError:
        pass
    return ' '.join(words)