Python REGEX returning NONE

Question

Working with this expression for find the words with at least 3 numbers: \b(?<=\s).*?[0-9]{1}.*?[0-9]{1}.*?[0-9]{1}.*?\b

I tested on Pythex and it works well... but I got NONE as result, can someone help?

infile:

IZN8TEIS
IZN89EIS
F7G74VCT
K8Z5PXJ8
O3HNWT3X
QY8479AG
R12PJ6XH
IZN8TEIS
JCON42W5

with open(infile) as fin, open(outfile, "w+") as fout:
    for line in fin:
        match = re.search(r"\b(?<=\s).*?[0-9]{1}.*?[0-9]{1}.*?[0-9]{1}.*?\b", line)
        *** IF I PRINT HERE MATCH .. ALWAYS NONE
    if match: fout.write(line)
    else: print(line)

Also tested with

pattern = re.compile("\b(?<=\s).*?[0-9]{1}.*?[0-9]{1}.*?[0-9]{1}.*?\b")
pattern.search(line)

same result.

As a general tip, you can group repeating subpatterns to make the expression more readable; for example `\b(?:[A-Z]*\d){3}\w*\b`. — oriberu, Dec 12 '22 at 02:52

score 0 · Answer 1 · answered Dec 12 '22 at 00:39

0

You regex is searching for lines that have a preceding whitespace (the (?<=\s) part of the regex).

It works when you test multiple lines as a single string. But in your Python code, you go through the lines in the file one at a time:

    for line in fin:
        ...

None of those lines has preceding whitespace, so the regex can't find a match.

You could join the lines in the file with a "\n" or read the entire contents at once some other way, and then run the search.

answered Dec 12 '22 at 00:39

Arseny

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It's not enough adding an space in front of each line? – Sergi Orrit Dec 12 '22 at 08:24
ok just removing the (?<=\s) was enough – Sergi Orrit Dec 12 '22 at 08:32
Yeah, any of those could fix your issue, I just offered one possible solution – Arseny Dec 12 '22 at 22:44

Python REGEX returning NONE

1 Answers1