My regex works on regex101 but doesn't work in python?

Question

So I need to match strings that are surrounded by |. So, the pattern should simply be r"\|([^\|]*)\|", right? And yet:

>>> pattern = r"\|([^\|]*)\|"
>>> re.match(pattern, "|test|")
<_sre.SRE_Match object at 0x10341dd50>
>>> re.match(pattern, "  |test|")
>>> re.match(pattern, "asdf|test|")
>>> re.match(pattern, "asdf|test|1234")
>>> re.match(pattern, "|test|1234")
<_sre.SRE_Match object at 0x10341df30>

It's only matching on strings that begin with |? It works just fine on regex101 and this is python 2.7 if it matters. I'm probably just doing something dumb here so any help would be appreciated. Thanks!

score 9 · Accepted Answer · answered Dec 15 '16 at 02:59

re.match will want to match the string starting at the beginning. In your case, you just need the matching element, correct? In that case you can use something like re.search or re.findall, which will find that match anywhere in the string:

>>> re.search(pattern, "  |test|").group(0)
'|test|'

>>> re.findall(pattern, "  |test|")
['test']

score 7 · Answer 2 · answered Mar 02 '20 at 16:17

In order to reproduce code that runs on https://regex101.com/, you have to click on Code Generator on the left handside. This will show you what their website is using. From there you can play around with flags, or with the function you need from re.

Note:

https://regex101.com/ uses re.MULTILINE as default flag
https://regex101.com/ uses re.finditer as default method

import re

regex = r"where"

test_str = "select * from table where t=3;"

matches = re.finditer(regex, test_str, re.MULTILINE)

for matchNum, match in enumerate(matches, start=1):

    print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group()))

    for groupNum in range(0, len(match.groups())):
        groupNum = groupNum + 1

        print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum)))

score 3 · Answer 3 · answered Dec 15 '16 at 02:59

3

Python offers two different primitive operations based on regular expressions: re.match() checks for a match only at the beginning of the string, while re.search() checks for a match anywhere in the string (this is what Perl does by default).

Document

answered Dec 15 '16 at 02:59

宏杰李

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Thanks, I knew it had to be something that dumb on my part. – mdong Dec 15 '16 at 03:04
This part is very confusing, so they write a Document for it. – 宏杰李 Dec 15 '16 at 04:06

My regex works on regex101 but doesn't work in python?

3 Answers3