python-regexHow to regex match excluding a word in Python?

To regex match excluding a word in Python, you can use the re.search() function with a negative lookahead assertion. The negative lookahead assertion is a special syntax that allows you to specify a pattern that should not be matched.

For example, the following code will match any string that contains the word cat but not the word dog:

import re

string = 'The cat is sleeping'

match = re.search(r'cat(?!.*dog)', string)

if match:
    print('Match found:', match.group())

Output example

Match found: cat

The code consists of the following parts:

• import re: imports the re module, which provides functions for working with regular expressions.
• string = 'The cat is sleeping': defines a string to search.
• match = re.search(r'cat(?!.*dog)', string): uses the re.search() function to search for the pattern cat(?!.*dog) in the string. The (?!.*dog) part is a negative lookahead assertion, which means that the pattern should not be followed by the word dog.
• if match:: checks if a match was found.
• print('Match found:', match.group()): prints the matched string.

Helpful links

• Python Regular Expressions
• Negative Lookahead Assertions

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