Match multiple lines in a file using regular expression python

Question

I have some many files each file has a set of lines in a given pattern. I want to match those multiple lines at once and do some operations on them such as delete, move to another file etc.

the multiple lines in a file are as given below.

self.unsupported_cmds = [r'\s*clns\s+routing',

                         r'\s*bfd\s+graceful-restart',

                         r'\s*ip\s+default-network',

                         r'\s*ip\s+default-gateway',

                         r'\s*ip\s+subnet-zero',

                         r'\s*ip\s+cef\s*$' ]

The lines within square brackets may vary.

Help me how to do it.

Please add four leading spaces for all the code. Formatting is a bit complicated to understand now. — lig
– lig, Commented Dec 16, 2011 at 6:13

lig · Accepted Answer · 2011-12-16 06:34:09Z

1

As python re module documentation says you may add the MULTILINE flag to re.compile method. This will let you match entire file at once.

import re

regex = re.match(r'''(
    ^\s*clns\s+routing$ |
    ^\s*bfd\s+graceful-restart$ |
    ^\s*ip\s+default-network$ |
    ^\s*ip\s+default-gateway$ |
    ^\s*ip\s+subnet-zero$ |
    ^\s*ip\s+cef\s*$
)+''', re.MULTILINE | re.VERBOSE)

Notice that I've added VERBOSE flag to write regex with additional formatting to make regex look nicer. Also you should see that there are several ^ and $ symbols. That is how multiline regex allows you to match over multiple lines in one file.

Additionally I must warn you that this regex will only help to match file just to be sure is entire file correctly formatted. If you want to parse data from this file you need to modify this regex a little to satisfy your needs.

Second code variant

import re

regex = re.match(r'''(^
    \s*
    (clns|bfd|ip)
    \s+
    (routing|graceful-restart|default-network|default-gateway|subnet-zero|cef)
$)+''', re.MULTILINE | re.VERBOSE)

edited Dec 16, 2011 at 6:34

answered Dec 16, 2011 at 6:16

lig

3,9481 gold badge28 silver badges40 bronze badges

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

7 Comments

Ameet Over a year ago

Could you please provide me the regular expression to match above set of lines?

Ameet Over a year ago

This is cool, but the lines with in the brackets many vary. Can you provide me a better solution?

lig Over a year ago

@ameet what you mean under word "vary"? I've added + that was missed. Now this regex will match any file that consists of the lines you've provided in any order.

Kirill Over a year ago

@ameet, you could use '|'.join(list_of_regexps) every time list_of_regexps changes.

lig Over a year ago

@ameet I've added second regex variant to let you additional example for better understanding. The second variant let you match the strings that consist of the any combination of the positional words from your question.

|

Collectives™ on Stack Overflow

Match multiple lines in a file using regular expression python

1 Answer 1

7 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

7 Comments

Your Answer

Sign up or log in

Post as a guest

Related