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I have a log file and I want to write a python script to parse out information from that log to another .txt file. I get stuck on how to start because I am very new to python. Could anyone shred some light on how I should do it

My log file contain:

06 May 19 03:40:35 3 abCodeClearTrap Error Clear Trap (agent: 12367a12, chassis:12367a12, ErrIdText: ERROR ID TEXT, csssi: EXTIFG, clearedID: 0x089088394)
06 May 19 03:44:35 3 abCodeErrorTrap Error Trap (agent: 12368a15, chassis: 12368a15, ErrIdText: Skip this item, csssi: SSRSSR, clearedID: 0x089088394)

Say the user want to parse the date, time, agent, Clear, and ErrIDText. How would I go about doing that. Thanks in advance

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  • The most robust way to parse strings would be the re module. A simpler solution that would easily mess up or break would be to .split() the strings and then refer to items by their index. Commented May 8, 2019 at 21:16

2 Answers 2

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The full answer to your question is a bit too much, but I can guide you a bit. You should read about regex, which you can use with the re module from python. So, I'll only parse dates from your strings:

import re
string='06 May 19 03:40:35 3 abCodeClearTrap Error Clear Trap (agent: 12367a12, chassis:12367a12, ErrIdText: ERROR ID TEXT, csssi: EXTIFG, clearedID: 0x089088394)\n\
06 May 19 03:44:35 3 abCodeErrorTrap Error Trap (agent: 12368a15, chassis: 12368a15, ErrIdText: Skip this item, csssi: SSRSSR, clearedID: 0x089088394)'

split_error=string.split('\n')

dates=[]
for error in split_error:
    date=re.match('\d{2} \w+ \d{2}', error).group(0)
    dates.append(date)

You could do this even more efficiently with list comprehensions, but if you're new to Python it's best to use more readable code.

I splitted every line of error into a list, and then searched for a combination of two numbers('\d{2}'), a space (), a word character or more ('\w+'), a space (), and then two numbers ( '\d{2}') in each string and extracted that from it. Then I appended the date to the dates list. You can find similar patterns to extract most of the data you're looking for.

Good luck !

Edit: as suggested by @Reedinationer, a good link to get to know patterns after reading a bit about the re module is the regex cheat sheet, I always go there when I forget how to do some regex

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Yes, as I said re would probably be what OP is looking for. If OP wants to learn more, they should click the link in my comment on their question. If you have a better link, Juan it would be great to include it in your post.
2

Here's a rough example how you can open your log file with open() and parse some values from it using the re module and str.split():

import re

with open('myfile.log') as f:
    lines = f.readlines()

data = []
for line in lines:

    date = re.match(r'\d{2} \w+ \d{2}', line).group(0)
    time = line.split()[3]
    agent = re.search(r'agent:\s(.*?),', line).group(1)        
    errID = re.search(r'ErrIdText:\s(.*?),', line).group(1)
    clear = re.search(r'clearedID:\s(.*?)\)', line).group(1)

    row = [date, time, agent, errID, clear]
    data.append(row)

for row in data:
    print(row)

Output:

['06 May 19', '03:40:35', '12367a12', 'ERROR ID TEXT', '0x089088394']
['06 May 19', '03:44:35', '12368a15', 'Skip this item', '0x089088394']
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5 Comments

say if I want to get the value "3" between time and abcCode. will I just do "ids = line.split()[1]"? thanks
@NickGonzales That would be ids = line.split()[4]. You should read up more on split from the documentation :)
When I execute the code. I got the error "date=re.match(r'/\d{2} \w+ \d{2}', line).group(0)....AttributeError: 'NoneType' object has no attribute 'group'
@NickGonzales You have an extra / on the start of that regex pattern. In general you can check for the match before calling group(0) on it to avoid errors. e.g. match = re.match(pattern, string); if match: date = match.group(0)
That was my typo on the comment. I did not have that extra "/" in my code and I still have the error. Thanks

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