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Last active Apr 13, 2019

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worked examples of argparse and python logging

argparse and logging sample code

#! /usr/bin/env python
"""Sample Code Demonstrating argparse and logging
Demonstrates appropriate logging techniques for a trivial command line program
that supports a variety of "verbosity" flags.
"""
import argparse
import logging
import logging.handlers
import os
import sys
import six
logger = logging.getLogger('owl.args.example')
logger.setLevel(logging.DEBUG)
# always write everything to the rotating log files
if not os.path.exists('logs'): os.mkdir('logs')
log_file_handler = logging.handlers.TimedRotatingFileHandler('logs/args.log', when='M', interval=2)
log_file_handler.setFormatter( logging.Formatter('%(asctime)s [%(levelname)s](%(name)s:%(funcName)s:%(lineno)d): %(message)s') )
log_file_handler.setLevel(logging.DEBUG)
logger.addHandler(log_file_handler)
# also log to the console at a level determined by the --verbose flag
console_handler = logging.StreamHandler() # sys.stderr
console_handler.setLevel(logging.CRITICAL) # set later by set_log_level_from_verbose() in interactive sessions
console_handler.setFormatter( logging.Formatter('[%(levelname)s](%(name)s): %(message)s') )
logger.addHandler(console_handler)
parser = argparse.ArgumentParser(
description="performs a variety of operations on a file.",
epilog="pretty neat, huh?",
fromfile_prefix_chars='@',
)
parser.add_argument('command', nargs="?", default="count", help="command to execute", choices=['count', 'head', 'tail'])
parser.add_argument('file', help="input filename", metavar='FILE')
parser.add_argument('-V', '--version', action="version", version="%(prog)s 0.17.2")
parser.add_argument('-m', '--maximum', type=int, default=1024**2, help="maximum file length to read", metavar='MAX')
parser.add_argument('-v', '--verbose', action="count", help="verbose level... repeat up to three times.")
parser.add_argument('-%', '--modulo', type=int, help="returns the length modulo this integer")
parser.add_argument('-g', '--guess', action="store_true", default=False, help="return a random guess instead of bothering to read the file. Because \"lazy\" programming is GOOD programming.")
def handle_count_command(args):
logger.warning("handling count command...")
if args.guess:
import random
logger.warn('taking a random guess!')
print(random.randint(0,args.maximum))
return
filename = args.file
try:
with open(filename, 'r') as input_file:
logger.info("opened file: {0}".format(filename))
logger.debug("file opened in read mode")
file_length = len(input_file.read(args.maximum))
if args.modulo:
logger.debug('computing the length modulo {:,} operator'.format(args.modulo))
file_length = file_length % args.modulo
logger.debug("read all data from file")
print('{filename}: {file_length}'.format( **locals() ))
logger.debug("closed file")
except IOError:
logger.error("file not found: {}".format(filename))
logger.critical("unable to count file!")
except Exception as e:
logger.critical("unknown error while attempting to read file length", exc_info=True)
six.reraise(*sys.exc_info())
def handle_head_command(args):
logger.warning("handling head command...")
filename = args.file
try:
with open(filename, 'rb') as input_file:
logger.debug("file opened in binary read mode")
print(input_file.read(256))
except IOError:
logger.error("file not found: {}".format(filename))
logger.critical("unable to head file!")
def set_log_level_from_verbose(args):
if not args.verbose:
console_handler.setLevel('ERROR')
elif args.verbose == 1:
console_handler.setLevel('WARNING')
elif args.verbose == 2:
console_handler.setLevel('INFO')
elif args.verbose >= 3:
console_handler.setLevel('DEBUG')
else:
logger.critical("UNEXPLAINED NEGATIVE COUNT!")
if __name__ == '__main__':
args = parser.parse_args()
set_log_level_from_verbose(args)
if args.command == 'count':
handle_count_command(args)
elif args.command == 'head':
handle_head_command(args)
else:
logger.error("Unknown command: {}".format(args.command))
#! /usr/bin/env python
"""Sample code diving deeper into argparse "subparsers" feature.
"""
import argparse
import logging
import logging.handlers
import os
logger = logging.getLogger('owl.args.example')
logger.setLevel(logging.DEBUG)
# always write everything to the rotating log files
if not os.path.exists('logs'): os.mkdir('logs')
log_file_handler = logging.handlers.TimedRotatingFileHandler('logs/args.log', when='M', interval=2)
log_file_handler.setFormatter( logging.Formatter('%(asctime)s [%(levelname)s](%(name)s:%(funcName)s:%(lineno)d): %(message)s') )
log_file_handler.setLevel(logging.DEBUG)
logger.addHandler(log_file_handler)
# also log to the console at a level determined by the --verbose flag
console_handler = logging.StreamHandler() # sys.stderr
console_handler.setLevel(logging.CRITICAL) # set later by set_log_level_from_verbose() in interactive sessions
console_handler.setFormatter( logging.Formatter('[%(levelname)s](%(name)s): %(message)s') )
logger.addHandler(console_handler)
parser = argparse.ArgumentParser(
description="performs a variety of operations on a file.",
epilog="pretty neat, huh?",
fromfile_prefix_chars='@',
)
parser.add_argument('-V', '--version', action="version", version="%(prog)s 2.0")
parser.add_argument('-v', '--verbose', action="count", help="verbose level... repeat up to three times.")
commands = parser.add_subparsers(dest="command", help="sub-commands")
count_parser = commands.add_parser("count", help="count the number of characters in a file")
count_parser.add_argument('file', help="input filename", metavar='FILE')
count_parser.add_argument('-m', '--maximum', type=int, default=1024**2, help="maximum file length to read", metavar='MAX')
count_parser.add_argument('-%', '--modulo', type=int, help="returns the length modulo this integer")
count_parser.add_argument('-g', '--guess', action="store_true", default=False, help="return a random guess instead of bothering to read the file. Because \"lazy\" programming is GOOD programming.")
head_parser = commands.add_parser("head", help="show the first 256 characters of a file")
head_parser.add_argument('files', nargs="+", help="input filename", metavar='FILE')
def handle_count_command(args):
logger.warning("handling count command...")
if args.guess:
import random
logger.warn('taking a random guess!')
print(random.randint(0,args.maximum))
return
filename = args.file
try:
with open(filename, 'r') as input_file:
logger.info("opened file: {0}".format(filename))
logger.debug("file opened in read mode")
file_length = len(input_file.read(args.maximum))
if args.modulo:
logger.debug('computing the length modulo {:,} operator'.format(args.modulo))
file_length = file_length % args.modulo
logger.debug("read all data from file")
print('{filename}: {file_length}'.format( **locals() ))
logger.debug("closed file")
except IOError:
logger.error("file not found: {}".format(filename))
logger.critical("unable to count file!")
except Exception as e:
logger.critical("unknown error while attempting to read file length", exc_info=True)
def handle_head_command(args):
logger.warning("handling head command...")
for filename in args.files:
try:
print(filename, ':')
with open(filename, 'rb') as input_file:
logger.debug("file opened in binary read mode")
print(input_file.read(256))
print()
logger.info("successfully finished heading file {}".format(filename))
except IOError:
logger.error("file not found: {}".format(filename))
logger.critical("unable to head file!")
def set_log_level_from_verbose(args):
if not args.verbose:
console_handler.setLevel('ERROR')
elif args.verbose == 1:
console_handler.setLevel('WARNING')
elif args.verbose == 2:
console_handler.setLevel('INFO')
elif args.verbose >= 3:
console_handler.setLevel('DEBUG')
else:
logger.critical("UNEXPLAINED NEGATIVE COUNT!")
if __name__ == '__main__':
args = parser.parse_args()
set_log_level_from_verbose(args)
if args.command == 'count':
handle_count_command(args)
elif args.command == 'head':
handle_head_command(args)
else:
logger.error("Unknown command: {}".format(args.command))
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