替换python中的特定单词

Question

If I have a string "this is", and I want to replace "is" to "was". When I use replace ("is", "was") , I got "thwas was", but what i am expecting is "this was", is there any solution?

Answer 1

You need to do something more sophisticated than a regular string replace. I'd suggest using Regular Expressions ( the re module ), and using the \\b escape sequence to match word boundaries :

import re
re.sub(r"\bis\b", "was", "This is the best island!")

Result: 'This was the best island!'

By using the pattern r"\\bis\\b" instead of just "is" , you ensure that you only match "is" when it appears as a stand-alone word (ie there are no numbers, letters or underscore characters directly adjacent to it in the original string).

Here's some more examples of what matches and what doesn't:

re.sub(r"\bis\b", "was", "is? is_number? is, isn't 3is is, ,is, is. hyphen-is. &is")

Result: "was? is_number? was, isn't 3is was, ,was, was. hyphen-was. &was"