Match whole word in string including special characters

May 16, 2023

I am aware of multiple existing answers that suggest:

def contains(string, word):
    return bool(re.search(rf"\b{word}\b", string))

But this pattern gives special treatment to alphanumeric character. For examples, contains("hello world!", "world!") returns False while contains("hello world!", "world") returns True.

I need a more ‘naive’ search pattern, one that matches a substring as long as it starts and ends with either the superstring’s boundary or a space. (Desired behavior: opposite of the examples above.)

>Solution :

You need to avoid using \b (word boundary) and assert that previous and next positions don’t have a non-whitespace character. Also it is safer to use re.escape as your search word may contain special regex meta characters.

You may use this python code:

def contains(string, word):
    return bool(re.search(rf"(?<!\S){word}(?!\S)", re.escape(string)))

print (contains("hello world!", "world"))
print (contains("hello world!", "world!"))

Output: