Python: match one of multiple regex patterns and extract IP address if match

Question

I am using python to parse Postfix logfiles. I need to match lines containing any of multiple patterns, and extract IP address if line matches

ip = re.search('^warning: Connection rate limit exceeded: [0-9]* from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\] for service smtp', message)
if not ip:
    ip = re.search('^NOQUEUE: reject: RCPT from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\]: .*: Relay access denied; .*', message)
    if not ip:
        ip = re.search('^NOQUEUE: reject: RCPT from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\]: .*:  Recipient address rejected: .*', message)
...
...
print ip.group(1)

Any line will only ever match one pattern. I know that normaly I can use '(pattern1|pattern2|pattern3)' to match any of multiple patterns, but since I am alredy using parenthesis () to group the IP address which I want to extract, I don't know how to do that.

I will have quite a lot of patterns to match. What would be the most clean/elegant way to do it ?

Please include your input, current output and expected output. — Forge
– Forge, Commented Mar 7, 2016 at 13:55

alecxe · Accepted Answer · 2016-03-07 13:57:00Z

3

You can use a non-capturing group:

patterns = [
    "warning: Connection rate limit exceeded: [0-9]* from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\] for service smtp",
    "NOQUEUE: reject: RCPT from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\]: .*: Relay access denied; .*",
    "NOQUEUE: reject: RCPT from .*\[([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})\]: .*:  Recipient address rejected: .*"
]
pattern = re.compile("^(?:" + "|".join(patterns) + ")")
ip = pattern.search(message)

answered Mar 7, 2016 at 13:57

alecxe

476k127 gold badges1.1k silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Martin Vegter Over a year ago

what does "^(?:" in the re.compile expression mean ?

alecxe Over a year ago

@MartinVegter ^ is the beginning of the string, (?:) is a non-capturing group itself.

Martin Vegter Over a year ago

it almost works, but when I do if ip: print ip.group(1), then it prints None. Obviously, it matched my pattern (because if ip evaluated as true), but it does not print the matched ip.

Martin Vegter Over a year ago

I see what's happening: ip.group(1) is None when the second pattern matched. In which case the ip is in ip.group(2). But I don't know which of my patterns matched. How can I print ip.group(n), where n is the only non-None value ?

alecxe Over a year ago

@MartinVegter got it, have you tried looking into groups()? Thanks.

Collectives™ on Stack Overflow

Python: match one of multiple regex patterns and extract IP address if match

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related