在特殊字符前添加空格

Question

如何在Python中创建RE，以便在这些特殊字符前面添加空格,?!如果这些特殊字符与一个单词？在

以下是输入字符串：

myString= 'I like him, but is he good? Maybe he is good , smart, and strong.'

所需输出（如果特殊字符不固定在一个单词上，则不会修改）：

^{pr2}$

我试过这个：

modifiedString= re.sub('\w,' , ' ,' ,myString)

但它给出了错误的结果。它删除coma之前的最后一个字符，结果示例如下：

modifiedString = 'I like hi , but is he good? Maybe he is goo , smar , and strong.'

有什么解决这个问题的建议吗？在

Answer 1

问题是你也在替换角色。您需要在regex中使用group来保存它，然后在替换字符串中指定group number。在

>>> myString = 'I like him, but is he good? Maybe he is good , smart, and strong.'
>>> re.sub(r'(\w)([,?!])' , r'\1 \2' ,myString)
'I like him , but is he good ? Maybe he is good , smart , and strong.'

Answer 2

您可以使用^{}：

>>> import re
>>> myString= 'I like him, but is he good? Maybe he is good , smart, and strong.'
>>> re.sub('(?<=\w)([!?,])', r' \1', myString)
'I like him , but is he good ? Maybe he is good , smart , and strong.'
>>>

(?<=\w)是与单词字符匹配的回溯断言。在

([!?,])是与字符集[!?,]匹配的捕获组（您可以在方括号内添加更多要匹配的字符）。在

\1是指([!?,])捕获的文本。在

Answer 3

作为另一种回答，您可以在不使用regex的情况下解决它，只需使用str.replace：

>>> rep_list=['?',',','!']
>>> for i in rep_list : 
...  if i in myString:
...   myString=myString.replace(i,' '+i)
... 
>>> myString
'I like him , but is he good ? Maybe he is good  , smart , and strong.'