Provides a class for creating and manipulating plain-text logfiles. MD5 checksums are used to verify the integrity of logfiles between sessions. A file of metadata for each log is also maintained. Includes an example of how to create and use a logpyl object.
Python, 220 lines
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"""The logpyl class implements basic logging functionality for Python programs.
A logpyl log consists of three files. The log file contains the events logged
to a logpyl object. The metadata file contains information about the log, such
as creation date, modification date, and name. The checksum file contains an MD5
hash created from the log and metadata files, and is used to check the integrity
of log files."""
def __init__(self,path='logs',name='NewLog',debug='off'):
"Initialize or open logs as log objects are instantiated."
import sys
import os.path
self.events = [] # list of events written to this log
self.debug = debug # flag to activate/deactive debugging messages
# First try the metadata file
self.metadatafile = name + '.lmd'
self.mdf = path + '/' + self.metadatafile
mfn = os.path.isfile(self.mdf)
if ( mfn ):
if ( debug == 'on' ):
print 'DEBUG: Metadata file',self.metadatafile,'exists.'
# Since the file exists, get the metadata
mfn = open(self.mdf,'r')
self.name = mfn.readline().strip()
self.path = mfn.readline().strip()
self.logfile = mfn.readline().strip()
self.metadatafile = mfn.readline().strip()
self.checksumfile = mfn.readline().strip()
self.created = mfn.readline().strip()
self.modified = mfn.readline().strip()
mfn.close()
self.ldf = path + '/' + self.logfile
self.cdf = path + '/' + self.checksumfile
else:
if ( debug == 'on' ):
print 'DEBUG: Metadata file',metadatafile,'does not exist.'
self.name = name
self.path = path
self.metadatafile = name + '.lmd'
self.logfile = name + '.log'
self.checksumfile = name + '.md5'
import time
self.created = time.asctime(time.localtime(time.time()))
self.mdf = path + '/' + self.metadatafile
self.ldf = path + '/' + self.logfile
self.cdf = path + '/' + self.checksumfile
# Then try the log file
lfn = os.path.isfile(self.ldf)
if ( lfn ):
if ( debug == 'on' ):
print 'DEBUG: Log file',self.logfile,'exists.'
lfn = open(self.ldf,'r')
for line in lfn.readlines():
self.events.append(line.strip())
lfn.close()
else:
if ( debug == 'on' ):
print 'DEBUG: Log file',self.logfile,'does not exist.'
# Finally, try the checksum file
cfn = os.path.isfile(self.cdf)
if ( cfn ):
if ( debug == 'on' ):
print 'DEBUG: Checksum file',self.checksumfile,'exists.'
cfn = open(self.cdf, 'r')
self.md5 = cfn.read().strip()
if ( debug == 'on' ):
print 'DEBUG: MD5 checksum',self.md5,'read from',self.checksumfile
cfn.close()
else:
if ( debug == 'on' ):
print 'DEBUG: Checksum file',self.checksumfile,'does not exist.'
pass
# Once we have read the metadata, verify the integrity of the logfiles.
self.verify()
def add(self, eventclass="note", message="Your message here"):
"Compose a log entry from the elements passed to add() and append it to the list of events."
import time
event = self.datetime() + ' ' + eventclass + ' ' + message
if ( self.debug == "on" ):
print 'DEBUG: Adding', event, 'to log', self.name
self.modified = time.asctime(time.localtime(time.time()))
self.events.append(event)
return
def close(self):
"Close the log by writing all log and metadata to the proper files. Also update the checksum file."
import sys
import os
"Write the current version of the log to a file and free the variables used by the log."
if ( self.debug == 'on' ):
print "DEBUG: Closing log", self.name
# If self.path does not exist, create the directory for the logfiles.
if ( not os.path.exists(self.path ) ):
if ( self.debug == 'on' ):
print 'DEBUG: Directory ',self.path,' does not exist. I am creating it now.'
try:
os.makedirs(self.path)
if ( self.debug == 'on' ):
print 'DEBUG: Created log file directory',self.path
except OSERROR:
print 'ERROR: Could not create log file directory',self.path
# Make sure that the metadata file is opened (created) and written.
import time
mfn = open(self.mdf, 'w+')
mfn.write(self.name+'\n')
mfn.write(self.path+'\n')
mfn.write(self.logfile+'\n')
mfn.write(self.metadatafile+'\n')
mfn.write(self.checksumfile+'\n')
mfn.write(self.created+'\n')
if ( not hasattr(self,'modified') ):
mfn.write(self.created+'\n')
else:
mfn.write(self.modified+'\n')
mfn.close()
# Make sure that the log entries are written.
lfn = open(self.ldf, 'w+')
for event in self.events:
lfn.write(event+'\n')
lfn.close()
# Create the MD5 checksum from the log file and metadata file
import md5
checksum = md5.new()
mfn = open(self.mdf, 'r')
for line in mfn.readlines():
checksum.update(line)
mfn.close()
lfn = open(self.ldf, 'r')
for line in lfn.readlines():
checksum.update(line)
lfn.close()
cs = checksum.hexdigest()
if ( self.debug == 'on' ):
print 'DEBUG: The MD5 digest of the metadata and log files is',cs
# Make sure that the checksum file is opened (created) and written to.
cfn = open(self.cdf,'w+')
cfn.write(cs+'\n')
cfn.close()
def datetime(self):
"Generate the date/time stamp used in our log entries"
import time
datestamp = time.asctime(time.localtime(time.time()))
return datestamp
def info(self):
print 'Info about log', self.name, ':'
print '\tName:', self.name
print '\tPath:', self.path
print '\tLog file:', self.logfile
print '\tMetadata file:', self.metadatafile
print '\tChecksum file:', self.checksumfile
if ( hasattr(self,'md5') ):
print '\t\tMD5 Checksum:',self.md5
print '\tNo. of entries:', len(self.events)
if ( hasattr(self,'created') ):
print '\tCreated:',self.created
if ( hasattr(self,'modified') ) :
print '\tModified:',self.modified
def printlog(self):
print '\nPrinting log', self.name
for event in self.events:
print event
print '\n'
def verify(self):
"Compute the MD5 checksum for this log to see if the logfiles have been corrupted."
# If there is no self.md5, no checksum exists for this log yet...
if ( not hasattr(self,'md5') ):
print 'WARNING: No MD5 checksum was found for log',self.name
print 'WARNING: Log',self.name,'may be newly created, or it may be corrupt!'
return
# Otherwise, create the MD5 checksum from the log file and metadata file for verification
import md5
checksum = md5.new()
mfn = open(self.mdf, 'r')
for line in mfn.readlines():
checksum.update(line)
mfn.close()
lfn = open(self.ldf, 'r')
for line in lfn.readlines():
checksum.update(line)
lfn.close()
cs = checksum.hexdigest()
if ( self.debug == 'on' ):
print 'DEBUG: The MD5 digest of the metadata and log files is',cs
if ( self.md5 == cs ):
if ( self.debug == 'on' ):
print 'DEBUG: The calculated MD5 checksum',cs,'matches the stored MD5 checksum',self.md5
else:
if ( self.debug == 'on' ):
print 'DEBUG: The calculated MD5 checksum',cs,'does not match the stored MD5 checksum',self.md5
print 'ERROR: The MD5 checksum for log',self.name,'is inconsistent!'
print 'ERROR: Log',self.name,'may be corrupt!'
if __name__ == '__main__':
# create a new log or open an existing log with debugging turned on
# (disable debugging messages by passing 'off' as the third parm to logpyl())
mylog = logpyl('logs','testlog','on')
# add a couple of events to the log
mylog.add("spam","Spam is US$1.95 per can.")
mylog.add("eggs","Eggs are US$0.89 per dozen.")
# print some summary information about the log
mylog.info()
# print the log entries
mylog.printlog()
# close the log
mylog.close()
|
I wanted to have a basic tool for maintaining a log file for an application during the development process. This class provides such a tool.
The error noted by Sam Spade (see comments) has been corrected.
Tags: debugging
Error in line. The following line is incorrect:
Instead it should read:
Thank you. Sam - Thanks! I missed that when I was rewriting part of the script. I hope that you found this code useful.