How Can I Use Regular Expressions to Match Whole Words in a String?

Match a Whole Word in a String Using Dynamic Regex

The task of matching a whole word in a string can be achieved using regex. However, creating multiple match expressions for different word locations can be tedious. This article delves into a concise solution using word boundaries.

Using Word Boundaries

Word boundaries, denoted by b, indicate the beginning or end of a word. By incorporating b into the regex pattern, we can match words surrounded by non-word characters. The following code demonstrates this:

match_string = r'\b' + word + r'\b'
# Or Python 3.7+ only versions:
match_string = r'\b{}\b'.format(word)
match_string = rf'\b{word}\b'

This regex pattern will match "word" as a whole word, regardless of its position in the string.

Matching Multiple Words

If multiple words need to be matched as whole words, we can use a list of words and create a pattern like this:

match_string = r'\b(?:{})\b'.format('|'.join(words))
# Or Python 3.7+ only version:
match_string = rf'\b(?:{"|".join(words)})\b'

In this pattern, the words are enclosed within a non-capturing group, ensuring that only whole words are matched.

Boundary Considerations

If the "words" to be matched contain special characters, they need to be escaped before using them in the regex pattern using re.escape().

For words that start or end with special characters, unambiguous word boundaries (?

In conclusion, using word boundaries provides a convenient way to match whole words in a string, eliminating the need for multiple match expressions based on word location.

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