{"id":124999,"date":"2022-05-20T15:27:39","date_gmt":"2022-05-20T15:27:39","guid":{"rendered":"https:\/\/blog.finxter.com\/?p=379866"},"modified":"2022-05-20T15:27:39","modified_gmt":"2022-05-20T15:27:39","slug":"your-python-regex-pattern-doesnt-match-try-this","status":"publish","type":"post","link":"https:\/\/sickgaming.net\/blog\/2022\/05\/20\/your-python-regex-pattern-doesnt-match-try-this\/","title":{"rendered":"Your Python Regex Pattern Doesn\u2019t Match? Try This!"},"content":{"rendered":"
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5\/5 – (1 vote) <\/div>\n<\/div>\n

Problem Formulation<\/h2>\n

Say, you want to find a regex<\/a> pattern in a given string. You know the pattern exists in the string. You use the re.match(pattern, string)<\/code> function to find the match object<\/a> where the pattern matches in the string.<\/p>\n

\"\ud83d\udcac\" Problem<\/strong>: The Python regular expression pattern is not found in the string. The pattern doesn’t match anything, and, thus, the match object is None<\/code>. How to fix this?<\/p>\n

Here’s an example in which you’re searching for the pattern 'h[a-z]+'<\/code> which should match the substring 'hello'<\/code>. <\/p>\n

But it doesn’t match! \"\u26a1\"<\/p>\n

import re my_string = 'hello world'\npattern = re.compile('h[a-z]+') match = re.match(pattern, my_string) if match: print('found!')\nelse: print('not found!')<\/pre>\n
Output:<\/p>\n
not found!<\/code><\/pre>\n
Where is the bug? And how to fix it, so that the pattern matches the substring 'hello'<\/code>?<\/p>\n
\"\ud83d\udca1\" Learn More<\/strong>: Improve your regex superpower by studying character classes<\/strong><\/em> used in the example pattern 'h[a-z]+'<\/code> by visiting this tutorial on the Finxter blog<\/a>.<\/p>\n
Solution: Use re.search() instead of re.match()<\/h2>\n
A common reason why your Python regular expression pattern is not matching in a given string is that you mistakenly used re.match(pattern, string)<\/code> instead of re.search(pattern, string)<\/code> or re.findall(pattern, string)<\/code>. The former attempts to match the pattern<\/code> at the beginning of the string<\/code>, whereas the latter two functions attempt to match anywhere in the string.<\/p>\n
Here’s a quick recap of the three regex functions:<\/p>\n