On 2017-07-12 23:49, Nick Mellor wrote:
On Wednesday, 12 July 2017 02:32:29 UTC+10, Ganesh Pal wrote:
Dear Python friends
I am trying to open a file and check if there is a pattern has changed
after the task got completed?
file data:
........................................................
#tail -f /file.txt
..........................................
Note: CRC:algo = 2, split_crc = 1, unused = 0, initiator_crc = b6b20a65,
journal_crc = d2097b00
Note: Task completed successfully.
Note: CRC:algo = 2, split_crc = 1, unused = 0, initiator_crc = d976d35e,
journal_crc = a176af10
I have the below piece of code but would like to make this better more
pythonic , I found regex pattern and exception handling poor here , any
quick suggestion in your spare time is welcome.
#open the existing file if the flag is set and check if there is a match
log_file='/file.txt'
flag_is_on=1
data = None
with open(log_file, 'r') as f:
data = f.readlines()
if flag_is_on:
logdata = '\n'.join(data)
reg = "initiator_crc =(?P<ini_crc>[\s\S]*?), journal_crc"
crc = re.findall(re.compile(reg), logdata)
if not crc:
raise Exception("Pattern not found in logfile")
checksumbefore = crc[0].strip()
checksumafter = crc[1].strip()
logging.info("checksumbefore :%s and checksumafter:%s"
% (checksumbefore, checksumafter))
if checksumbefore == checksumafter:
raise Exception("checksum not macthing")
I am on Linux and Python 2.7
Regards,
Ganesh
There's not much need to compile regexes unless you've got *a lot* of them in
your code. The first ones are automatically compiled and cached:
https://stackoverflow.com/questions/452104/is-it-worth-using-pythons-re-compile
I think this is the first time that I've seen someone pass a compiled
pattern into re.findall.
The usual way is to pass the pattern as a string:
crc = re.findall(reg, logdata)
If you have a lot of them, or it's in a loop that'll iterate many times,
it'll be quicker if you compile it first (outside the loop):
pattern = re.compile(reg)
and then use the compiled pattern's .findall method:
crc = pattern.findall(logdata)
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