printing dates in a log file

Question

I have a log file with a consistent date in my log file.

ex:

date1

date2

...

The date means the number of logs in my log file. I was wondering how can print the dates from the log file using Regular expressions

what I have tried:

import re

dateRegex = re.compile('^\w{3}\s\d\d:\d\d:\d\d')

f = open("logfile.log","r")

for line in f.readlines():
    matches = re.findall(dateRegex,line)
    print matches

The output I am getting is (many []):

[]
[]
[]
...
...

Put an if somewhere to avoid printing when you have no matches. You might also want to print the element of the result list, as opposed to the list itself. — Jerry
– Jerry, Commented Jan 16, 2014 at 17:11
You forgot to match the date. Try r'^\w{3}\s\d\d\s\d\d:\d\d:\d\d' — Jerry
– Jerry, Commented Jan 16, 2014 at 17:13
@Jerry no matches still =/ I was wondering is the r is needed when using re.compile? i tested it without the r for another case and it worked without it — Liondancer
– Liondancer, Commented Jan 16, 2014 at 17:15
@Jerry if you could write this as the answer I would gladly accept it thanks! — Liondancer
– Liondancer, Commented Jan 16, 2014 at 17:18

Jerry · Accepted Answer · 2014-01-16 17:26:31Z

1

You seem to have forgotten the date:

import re

dateRegex = re.compile(r'^\w{3}\s\d\d?\s\d\d:\d\d:\d\d')
                             # ^^^^^^^ I added ? to cater for dates between 1 & 9

f = open("logfile.log","r")

for line in f.readlines():
    matches = re.findall(dateRegex,line)
    if matches:                # Check if there are matches
        print matches[0]       # Print first element of list returned by findall

I think that you can use re.match instead, since you're testing line by line and using the beginning of line anchor:

import re

dateRegex = re.compile(r'\w{3}\s\d\d?\s\d\d:\d\d:\d\d')

f = open("logfile.log","r")

for line in f.readlines():
    matches = re.match(dateRegex,line)
    if matches:
        print matches.group()

answered Jan 16, 2014 at 17:26

Jerry

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