Regex to return lines starting with specific pattern in a text file-CodePudding

Here is my text file:

    --- config-archive/2022-12-21/R1.txt

    new

@@ -1,6  1,6 @@

 Building configuration...
 
-Current configuration : 1106 bytes
 Current configuration : 1089 bytes
 !
 version 12.4
 service timestamps debug datetime msec
@@ -94,7  94,7 @@

 !
 !
 !
-banner motd ^Cthis is changed through config pushing script^C
 banner motd ^Cyoyoyoyo i just changed this^C
 !
 line con 0
  exec-timeout 0 0

I need the program to return lines starting with a single - or from the text file.

My approach is looping through the file and search the pattern as a string which I do not find to be efficient. So need regex to do it in an efficient way. Thank you.

CodePudding user response：

This sounds awfully like an AB question, but here's your solution using RegEx:

^[- ].

^: Matches start of the line
[- ]: Matches a minus or a plus
. : Matches any character after that until the end of the line

Consider using just Python though- it might be faster, and definitely easier to read:

data = " ... "

lines = [line for line in data.splitlines()
         if line.startswith(' ') or line.startswith('-')]

CodePudding user response：

Try this:

import re

pattern = r'^[- ](?![- ])'  # Match lines that start with a single `-` or ` ` and do not have a `- and  ` immediately after

with open('your_text_file.txt', 'r') as f:
    for line in f:
        if re.match(pattern, line):
            print(line)