Python read log files and get lines containing specific words

Question

I have log files ( named in the format YYMMDD ) and I\'d like to create a script that get only important information from the files ( like the lines that contains \"O:NVS:V

Answer 1

This should get you started nicely:

infile = r"D:\Documents and Settings\xxxx\Desktop\test_log.txt"

important = []
keep_phrases = ["test",
              "important",
              "keep me"]

with open(infile) as f:
    f = f.readlines()

for line in f:
    for phrase in keep_phrases:
        if phrase in line:
            important.append(line)
            break

print(important)

It's by no means perfect, for example there is no exception handling or pattern matching, but you can add these to it quite easily. Look into regular expressions, that may be better than phrase matching. If your files are very big, read it line by line to avoid a MemoryError.

Input file:

This line is super important!
don't need this one...
keep me!
bla bla
not bothered
ALWAYS include this test line

Output:

['This line is super important!\n', 'keep me!\n', 'ALWAYS include this test line']

Note: This is Python 3.3.

Answer 2

You'll need to know how to loop over files in a directory, regular expressions to make sure your log file format matches to file you are looping over, how to open a file, how to loop over the lines in the open file, and how to check if one of those lines contains what you are looking for.

And here some code to get you started.

with open("log.log" 'r') as f:
    for line in f:
        if "O:NVS:VOICE" in line:
            print line