python multiple occurrence regex in a dynamic way

Question

I am trying a dynamic regex pattern whose occurrence is not known, for instance

ip = '3.3.3.5'
stt ="""
(1.1.1.1/32, 3.3.3.5/32), abcd: xx:xx:xx, abv cd
value: eth1/1 , bbcc , time: tt:tt
text :
eth1/1 ip time << 
eth1/2 ip time <<
 """

what i need to retrieve is , based on the ip i need to get the interface , in the above example , for 3.3.3.5/32 ip , i want to get the interface under "text:" which is eth1/1 and eth1/2

Regex i have used :

re.findall(ip+"[\/0-9,)]+\s+abcd: xx:xx:xx, abv cd\s+value: [0-9a-zA-Z\/]+ , bbcc , time: tt:tt\s+ values text\s+[0-9a-zA-Z\/]+",stt)

output : ['3.3.3.5/32), abcd: xx:xx:xx, abv cd\n value: eth1/1 , bbcc , time: tt:tt\n values text\n  eth1/1']

It returns the first occurrence which is eth1/1, but i am not aware how to get both the interfaces, pls guide

Why not 1.1.1.1/32 ? Additionally, use the newer regex module which supports \G. — Jan
– Jan, Commented May 1, 2017 at 16:42
the second ip is mandate , first one is optional , my main requirement is the output under text:. — rajpython
– rajpython, Commented May 1, 2017 at 16:46

mVChr · Accepted Answer · 2017-05-01 17:05:49Z

2

If you just want the output under text: then why not simply:

stt.split('text:', 1)[1].strip()

answered May 1, 2017 at 17:05

mVChr

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3 Comments

rajpython Over a year ago

i need to traverse the full string , ip should match and the text: is retrieved.

alexis Over a year ago

@raj why? What problem does this solution cause you?

rajpython Over a year ago

what u shared is good , but i need to check a condition like , ip should match first , then the data under text: need to grepped.

Jan · Accepted Answer · 2017-05-01 17:01:43Z

1

You could do it as follows:

import regex as re

string = """
(1.1.1.1/32, 3.3.3.5/32), abcd: xx:xx:xx, abv cd
value: eth1/1 , bbcc , time: tt:tt
text :
eth1/1 ip time << 
eth1/2 ip time <<

(1.1.1.1/32, 3.3.4.5/32), abcd: xx:xx:xx, abv cd
value: eth1/1 , bbcc , time: tt:tt
text :
eth1/1 ip time << 
eth1/2 ip time <<

(1.1.1.1/32, 3.3.5.5/32), abcd: xx:xx:xx, abv cd
value: eth1/1 , bbcc , time: tt:tt
text :
eth1/1 ip time << 
eth1/2 ip time <<
"""

rx = re.compile(r'''
        (?:
            \G(?!\A)
            |
            (?P<ip>\d+\.\d+\.\d+\.\d+)/32\)
        )
        (?s:
            (?:(?!^\().)*?
        )
        ^
        (?P<interface>eth\S+)
        \K
    ''', re.VERBOSE|re.MULTILINE)

result = {}; ip = None;
for match in rx.finditer(string):
    if match.group('ip'):
        ip = match.group('ip')
    try:
        result[ip].append(match.group('interface'))
    except:
        result[ip] = [match.group('interface')]

print(result)
# {'3.3.4.5': ['eth1/1', 'eth1/2'], '3.3.3.5': ['eth1/1', 'eth1/2'], '3.3.5.5': ['eth1/1', 'eth1/2']}

This assumes the structure above (IP addresses in parentheses) and uses the second address found.
See a demo on regex101.com.

answered May 1, 2017 at 17:01

Jan

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4 Comments

rajpython Over a year ago

iam using Python 2.7.3. is regex module available for this ?

Jan Over a year ago

Yup, it is, simply pip install regex.

rajpython Over a year ago

just curious , why regex , why not with re alone ?

Jan Over a year ago

@rajpython: \G is not supported in re - try it out, it won't work.

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