Python 3.6:在字符串中移动单词

Question

我知道这个函数在字符串中的字符周围移动，如下所示：

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

这允许我这样做：

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，所以我不只是在字母周围移动？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

你可以做这样的事情：

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)

Answer 2

带有正则表达式和替换函数(可以使用lambda和双三元来完成，但这并不真正可读(

匹配所有单词 (w+( 并与两个单词进行比较(不区分大小写(。如果找到，则返回"相反"单词。

import re
def swapping(a,b,c):
def matchfunc(m):
g = m.group(1).lower()
if g == c.lower():
return b.upper()
elif g == b.lower():
return c.upper()
else:
return m.group(1)
return re.sub("(w+)",matchfunc,a)
print(swapping("Boys and girls left the school.", "boys", "girls"))
print(swapping("Boys and girls left the school.", "GIRLS", "bOYS"))

均打印：GIRLS and BOYS left the school.

Answer 3

使用split函数获取由whitespaces分隔的单词列表

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

如果要将字符串作为参数传递，请使用.index()获取要交换的字符串的索引。

def swapping(a, b, c):
x = a.split(" ")
index_1 = x.index(b)
index_2 = x.index(c)
x[index_2], x[index_1] = x[index_1], x[index_2]
return ' '.join(x)

Answer 4

您要在此处执行两个单独的操作：交换和更改字符大小写。

前者在其他答复中已述及。

后者可以通过以不区分大小写的方式搜索单词来完成，但替换为输入单词，保留大小写。

def swapping(word_string, word1, word2):
# Get list of lowercase words
lower_words = word_string.lower().split()
try:
# Get case insensitive index of words
idx1 = lower_words.index(word1.lower())
idx2 = lower_words.index(word2.lower())
except ValueError:
# Return the same string if a word was not found
return word_string
# Replace words with the input words, keeping case
words = word_string.split()
words[idx1], words[idx2] = word2, word1
return ' '.join(words)
swapping("Boys and girls left the school.", "GIRLS", "BOYS")
# Output: 'GIRLS and BOYS left the school.'