regular expression to extract multiline line from a file in Python

Question

I am trying to write a regular expression to extract multiline line from a file that has system call trace. I try to find a system call trace for the error that happens. It is a debugging project. My goal to extract all line between keywords "Before Error" and "After Error" Here are my tries. https://repl.it/@kaloon/LiquidDimgrayParser

May I know what a problem with it?

Can you post an example error message? It's hard to write any regex pattern without seeing knowing exactly what the text looks like. — Tim
– Tim, Commented Nov 21, 2018 at 20:30
the text available on the link at the main post. Just click on the link — kaloon
– kaloon, Commented Nov 21, 2018 at 20:38
@kaloon: It is actually preferred here to have searchable code within the question. — guidot
– guidot, Commented Nov 21, 2018 at 21:04

Tim · Accepted Answer · 2018-11-21 20:57:27Z

1

Something like the following should work for you:

import re
pattern = re.compile(".*Before Error(.*)After Error.*", re.DOTALL)
pattern.findall(str1)

edited Nov 21, 2018 at 20:57

answered Nov 21, 2018 at 20:29

Tim

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5 Comments

Tim Over a year ago

I updated it with a working version, tested in your link.

kaloon Over a year ago

Thanks. It works :) . But What about If I want to just extract the line between them without extract the same the line that has "Before Error " and "After Error"

Tim Over a year ago

Using pattern = re.compile(".*Before Error[^\n]*\n(.*)\n.*After Error.*", re.DOTALL) should exclude the lines containing "Before Error" and "After Error".

kaloon Over a year ago

Hi Tim, I tried the last update. it got an empty result.

Tim Over a year ago

I'm not sure - for me, the second pattern returns the following:

['[pid 16701] 16:08:36 getuid()           = 10114\n[pid 16701] 16:08:36 getuid()           = 10114\n[pid 16701] 16:08:36 ioctl(8, BINDER_WRITE_READ, 0x7fc4f92e88) = 0\n[pid 16701] 16:08:36 ioctl(8, BINDER_WRITE_READ, 0x7fc4f92e88) = 0\n\xe2\x80\xa6[pid 16701] 16:08:36 ioctl(47, ASHMEM_GET_SIZE, 0) = 84\n[pid 16701] 16:08:36 close(47)          = 0\n[pid 16701] 16:08:36 getuid()           = 10114']

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