如何编写涵盖特定单词的大小写字母的正则表达式？

Question

I am trying to use regular expression to find a specific word (with small or capital letters) in a text.

Examples are:

• none
• None
• NONE

However, the following code doesn't find the pattern in sample texts.

import re

txt_list = ["None" , "none", "[none]", "(NONE", "Hi"]
pattern = "/\bnone\b/i"


for txt in txt_list:
    if re.search(pattern, txt):
        print(f'Found {txt}')

What is the cause of the above issue? Is the "pattern" incorrect?

Answer 1

Do not use slashes to delimit the regular expression. The syntax in Python is different. You can use (?i) to ignore case. (Additionally, escape the backslashes or use raw strings.)

pattern = "(?i)\\bnone\\b"

You can also pass the re.IGNORECASE flag to re.search .

pattern = r"\bnone\b"
for txt in txt_list:
    if re.search(pattern, txt, re.IGNORECASE):
        print(f'Found {txt}')