Python Regular Expression to fetch data from string

Question

I'm writing my first Python re code and i have some doubt regarding the Regular Expression. I have a variable which contains

a = "'PoE Port Info','1      up     medium    Auto Class         Searching             0       0.0         0           0.0','10     up     low       User defined 4(W) Searching             -       0.0         0           0.0'"

I need to extract:

'1      up     medium    Auto Class         Searching             0       0.0         0           0.0'

and convert the string to list of string with all whitespaces removed

['1','up','medium','Auto Class','Searching','0','0.0','0','0.0']

similarly

'10     up     low       User defined 4(W) Searching             -       0.0         0           0.0'

remove the whitespaces and convert to list

['10','up','low','User defined,'4(W)','Searching','-','0.0','0','0.0']

all the other remaining data in that string should not match.

My code:

a = "'PoE Port Info','1      up     medium    Auto Class         Searching             0       0.0         0           0.0','10     up     low       User defined 4(W) Searching             -       0.0         0           0.0'"
b= []
#split string with ,
a = a.split(",")
print(a)
for item in a:
    c = re.findall(r"[0-9]+[\s+[a-z]+]*[0-9]+",item, re.I)
    if c:
        #Replace whitespace character to spaces
        temp = re.sub(r'[\s]+',' ', c[0])
        #print(temp)
        b.append(temp.split(" "))
print(b)

This code is working but i'm facing issue at Regular expression. My current output:

[['1', 'up', 'medium', 'Auto', 'Class', 'Searching', '0'], ['10', 'up', 'low', 'User', 'defined', '4']]

Some please help me.

How to write the RE?

It can be done without the regex too you know. It looks like a CSV line converted to a string. If you're reading from a file it would be even easier. Let me know if you need a working code. — Nikhil Wagh
– Nikhil Wagh, Commented Apr 15, 2020 at 8:34
Perhaps remove the ' at the start and end of the string and split on 2 or more whitespace chars [^\S\r\n]{2,} regex101.com/r/edL69K/1 — The fourth bird
– The fourth bird, Commented Apr 15, 2020 at 8:37

Wiktor Stribiżew · Accepted Answer · 2020-04-15 11:37:38Z

1

If you know there is no need to check for nested/escaped single quotes, you may simply extract all the fields with a single regex that will capture all the fields in one go. The problem is with the fourth field that may contain any (amount of) chars, so you need to spell out the patterns for the other fields.

Here is an example regex:

import re
a = "'PoE Port Info','1      up     medium    Auto Class         Searching             0       0.0         0           0.0','10     up     low       User defined 4(W) Searching             -       0.0         0           0.0'"
res = re.findall(r"(?!^)'(\d+)\s+(\w+)\s+(\w+)\s+([^']*?)\s+(\S+)\s+(\S+)\s+([\d.]+)\s+(\d+)\s+([\d.]+)'", a)
print(res)
# => [
#       ('1', 'up', 'medium', 'Auto Class', 'Searching', '0', '0.0', '0', '0.0'), 
#       ('10', 'up', 'low', 'User defined 4(W)', 'Searching', '-', '0.0', '0', '0.0')
#    ]

See the regex demo and the Python demo

Details

(?!^)' - a ' not at the start of the string
(\d+) - Group 1: one or more digits
\s+ - 1+ whitespaces
(\w+)\s+ - Group 2: one or more word chars and then 1+ whitespaces
(\w+)\s+ - Group 3: one or more word chars and then 1+ whitespaces
([^']*?)\s+ - Group 4: any 0 or more chars other than ' as few as possible, then 1+ whitespaces
(\S+)\s+ - Group 5: any 1+ non-whitespaces, then 1+ whitespaces
(\S+)\s+ - Group 6: any 1+ non-whitespaces, then 1+ whitespaces
([\d.]+)\s+ - Group 7: any 1+ digits/dots, then 1+ whitespaces
(\d+)\s+ - Group 8: any 1+ digits, then 1+ whitespaces
([\d.]+) - Group 9: any 1+ digits/dots
' - a ' char.

edited Apr 15, 2020 at 11:37

answered Apr 15, 2020 at 11:30

Wiktor Stribiżew

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1 Comment

Nikhil K Murali Over a year ago

Hey, Thanks for the code. its working. what you said is true. fourth field is the issue, which I didn't know how to solve. Thank for your time.

xtlc · Accepted Answer · 2020-04-15 08:30:17Z

1

I suggest you use an online regex editor like regex 101 and test your teststring there - it is much easier to create a valid syntax there and in the match information window you also see which group is what.

I would probably try to create a set of x groups (one for each value you need). No need for split and other operations afterwards.

answered Apr 15, 2020 at 8:30

xtlc

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