python open large log file

Question

I use python open large log file like

Thu Oct  4 23:14:40 2012 [pid 16901] CONNECT: Client "66.249.74.228"
Thu Oct  4 23:14:40 2012 [pid 16900] [ftp] OK LOGIN: Client "66.249.74.228", anon     password "googlebot@google.com"
Thu Oct  4 23:17:42 2012 [pid 16902] [ftp] FAIL DOWNLOAD: Client "66.249.74.228",   "/pub/10.5524/100001_101000/100039/Assembly-2011/Pa9a_assembly_config4.scafSeq.gz",  14811136 bytes, 79.99Kbyte/sec
Fri Oct  5 00:04:13 2012 [pid 25809] CONNECT: Client "66.249.74.228"
Fri Oct  5 00:04:14 2012 [pid 25808] [ftp] OK LOGIN: Client "66.249.74.228", anon password "googlebot@google.com"
Fri Oct  5 00:07:16 2012 [pid 25810] [ftp] FAIL DOWNLOAD: Client "66.249.74.228", "/pub/10.5524/100001_101000/100027/Raw_data/PHOlcpDABDWABPE/090715_I80_FC427DJAAXX_L8_PHOlcpDABDWABPE_1.fq.gz", 14811136 bytes, 79.99Kbyte/sec
Fri Oct  5 00:13:19 2012 [pid 27354] CONNECT: Client "1.202.186.53"
Fri Oct  5 00:13:19 2012 [pid 27353] [ftp] OK LOGIN: Client "1.202.186.53", anon password "mozilla@example.com"

I want to read the lines from the end of file like tail command to get the recently 7 days record.

Here is my code, how can i change it.

import time
f= open("/opt/CLiMB/Storage1/log/vsftp.log")
def OnlyRecent(line):
   if  time.strptime(line.split("[")[0].strip(),"%a %b %d %H:%M:%S %Y")>     time.gmtime(time.time()-(60*60*24*7)): 
    return True
return False
filename= time.strftime('%Y%m%d')+'.log'
f1= open(filename,'w')
for line in f:
 if OnlyRecent(line):
        print line
        f1.write(line)
f.close()
f1.close()

http://stackoverflow.com/questions/136168/get-last-n-lines-of-a-file-with-python-similar-to-tail — NIlesh Sharma, Dec 03 '12 at 07:45

score 3 · Accepted Answer · answered Dec 03 '12 at 08:18

3

Use file.seek() to jump to some offset from the end of a file. For example, to print the last 1Kb of a file without reading the beginning of a file, do this:

with open("/opt/CLiMB/Storage1/log/vsftp.log") as f:
     f.seek(-1000, os.SEEK_END)
     print f.read()

answered Dec 03 '12 at 08:18

Raymond Hettinger

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Hi it say NameError: name 'os' is not defined – AntiGMO Dec 04 '12 at 08:52
can i directly add f.seek(-1000, os.SEEK_END) follow the f= open("/opt/CLiMB/Storage1/log/vsftp.log") in my program – AntiGMO Dec 04 '12 at 08:53
@JesseSiu import os, and I think you can directly add f.seek ..., though with ... is preferred. – sunqiang Dec 04 '12 at 15:47

score 0 · Answer 2 · answered Dec 03 '12 at 08:19

I didn't check this, just reformat code:

less verbose import from time module
dropwhile instead of for..if
with context to open/close files
PEP8
miscs

-

from time import time, gmtime, strptime
from itertools import dropwhile

deadline = gmtime(time()-(60*60*24*7))
formatting = "%a %b %d %H:%M:%S %Y"

def not_recent(line):
    return strptime(line.split("[")[0].strip(), formatting) <= deadline

with open("/opt/CLiMB/Storage1/log/vsftp.log") as f:
    filename = time.strftime('%Y%m%d')+'.log'
    with open(filename,'w') as f1:
        for line in dropwhile(not_recent, f):
            print line
            f1.write(line)

Abhijit · Answer 3 · 2012-12-03T08:35:58.650

Another Implementation, considering you are dealing with huge log files

def tail(fname, n):
    fin = os.open(fname,os.O_RDONLY ) #Get an open file desc
    size = os.fstat(fin).st_size #Get the size from the stat
    fin = os.fdopen(fin) #Convert fd to file obj
    count = 0
    fin.seek(size) #Seek to the end of the file
    try:
        while count < n: #Loop until the count of newlines exceed the tail size
            pos = fin.tell() - 2 #Step backward
            if pos == -1: #Until you are past the begining
                raise StopIteration #When you end the Loop
            fin.seek(pos)
            if fin.read(1) == '\n': #And check if the next character is a new line
                count += 1 #Maintaining the count
    except StopIteration:
        pass

    return fin

Usage

for e in tail("Test.log",10):
    print e

python open large log file

3 Answers3