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python get changed (non-default) cli arguments?

Given an argument parser with n arguments, where I change the default value of only a small subset every run from the command line, is there a clean way of extracting a dict/namespace of all the non-default k,v arguments?
parser = argparse.ArgumentParser()
parser.add_argument("--a",type=str,default='a')
parser.add_argument("--b",type=str,default='b')
parser.add_argument("--c",type=str,default='c')
parser.add_argument("--d",type=str,default='d')
And
python run.py --a "e"
I would like to have
def main():
parser = argparse.ArgumentParser()
parser.add_argument("--a",type=str,default='a')
parser.add_argument("--b",type=str,default='b')
parser.add_argument("--c",type=str,default='c')
parser.add_argument("--d",type=str,default='d')
non_default = parse_non_default(parser) # non_default = {'a':'e'}

You could lookup the parser and compare which values differenciate:
import argparse
def main():
parser = argparse.ArgumentParser()
parser.add_argument("--a", type=str, default='a')
parser.add_argument("--b", type=str, default='b')
parser.add_argument("--c", type=str, default='c')
parser.add_argument("--d", type=str, default='d')
parser.add_argument("--n", type=int, default=999)
args = parser.parse_args(['--a', 'e']) # Test CLI arguments!
non_default = {
opt.dest: getattr(args, opt.dest)
for opt in parser._option_string_actions.values()
if hasattr(args, opt.dest) and opt.default != getattr(args, opt.dest)
}
print(non_default)
main()
Out:
{'a': 'e'}

argparse - how to pass argument from args into function?

import argparse
from queries import most_common_cities
parser = argparse.ArgumentParser(description='A script that does operations with database data and returns values')
parser.add_argument('-c', '--most_common_cities',
nargs=1,
type=positive_int,
help='Specify how many common cities.')
args = parser.parse_args()
if args.most_common_cities:
result = most_common_cities(n) # "n" should be an arg passed by user
print(result)
How could I pass arguments from CLI to my function arg?
When someone use command:
python argp.py --most_common_cities 5
It should return 5 most common cities.

Remove nargs=1, then args.most_common_cities will be the actual value passed in.
nargs=1 wraps it in a list.
parser.add_argument('-c', '--most_common_cities',
type=int,
help='Specify how many common cities.')
args = parser.parse_args(['-c', '5'])
n = args.most_common_cities
print(n)
print(type(n))
# 5
# <class 'int'>

I started your script with following command:
python3 test.py --most_common_cities 5
You can access the arguments with:
import argparse
parser = argparse.ArgumentParser(description='A script that does operations with database data and returns values')
parser.add_argument('-c', '--most_common_cities',
nargs=1,
type=int,
help='Specify how many common cities.')
args = parser.parse_args()
arguments = vars(parser.parse_args())
print(arguments) #{'most_common_cities': [5]}
#then you can access the value with:
arguments['most_common_cities']

Selected options activate right subparsers

I have to invoke my script in this way.
script.py multiple --ways aa bb -as abab -bs bebe
In this case -as abab reffers to "aa" option from --ways parameter and -bs bebe to "bb" option.
And all chosed options should affect what "fulfill" method will be used.
If we chose 'aa' and 'bb' there should only be options '-as' and '-bs' not '-cs'.
import sys
from argparse import ArgumentParser
def fulfill_aa_parser(aa_parser):
aa_parser.add_argument('--ass', '-as', type=str, required=True, choices=['abababa'])
def fulfill_bb_parser(aa_parser):
aa_parser.add_argument('--bass', '-bs', type=str, required=True, choices=['bebebe'])
def fulfill_cc_parser(aa_parser):
aa_parser.add_argument('--cass', '-cs', type=str, required=True, choices=['cycycyc'])
def fulfill_multiple_parser(multiple_parser):
multiple_parser.add_argument('--ways', '-w', type=str, choices=['aa','bb', 'cc'], nargs='+', required=True)
def main(argv):
parser = ArgumentParser(description='TEST CASE')
subparsers = parser.add_subparsers(dest='type')
multiple_parser = subparsers.add_parser(
'multiple'
)
aabbparsers = multiple_parser.add_subparsers()
aa_parser = aabbparsers.add_parser('aa')
bb_parser = aabbparsers.add_parser('bb')
cc_parser = aabbparsers.add_parser('cc')
fulfill_multiple_parser(multiple_parser)
fulfill_aa_parser(aa_parser)
fulfill_bb_parser(bb_parser)
fulfill_cc_parser(cc_parser)
args = parser.parse_args(argv)
if args.type is None:
parser.print_help()
return
if __name__ == '__main__':
main(sys.argv[1:])
Parsing this in this way:
fulfill_aa_parser(multiple_parser)
fulfill_bb_parser(multiple_parser)
fulfill_cc_parser(multiple_parser)
will lead to parser always asking for '-as', '-bs' ,'-cs' and options in '--ways' will not affect this
EDIT : \
This is it looks when there is some thought put to it.
Just simply pass parser to this function
def fulfill_apple_argparser(parser):
parser.add_argument("--apple_argument")
def fulfill_banana_argparser(parser):
parser.add_argument("--banana_argument")
def fulfill_peach_argparser(parser):
parser.add_argument("--peach_argument")
def many_fruits_parse(parser, progs=None, list_of_fruits=('apple', 'banana', 'peach')):
progs = progs or []
if len(list_of_fruits) == 0 or parser in progs:
return
fulfill = {'apple': fulfill_apple_argparser, 'banana': fulfill_banana_argparser,
'peach': fulfill_peach_argparser}
subparsers = parser.add_subparsers(title='subparser', dest=parser.prog)
progs.append(parser)
for fruit in list_of_fruits:
secondary = [x for x in list_of_fruits if x != fruit]
fruit_parser = subparsers.add_parser(fruit, help=fruit)
fulfill[fruit](fruit_parser)
many_fruits_parse(fruit_parser, progs, secondary)

add_subparsers creates a special kind of positional argument, one that uses the add_parser command to create choices. Once a valid choice is provided, parsing is passed to that parser.
With
script.py multiple --ways aa bb -as abab -bs bebe
parser passes the task to multiple_parser. The --ways optional then gets 2 values
Namespace(ways=['aa','bb'])
Neither of those strings is used as a value for aabbparsers, and multiple_parser doesn't know what to do with '-as` or '-bs', and (I expect) will raise an error.
With:
script.py multiple aa -as abab
parsing is passed from parser to multiple_parser to aa_parser, which in turn handles '-as abab', producing (I think)
Namespace(as='abab')
Nesting as you do with multiple and aa is the only way to use multiple subparsers. You can't have two subparses 'in-parallel' (e.g. 'aa' and 'bb').
Especially when testing it's a good idea to provide a dest to the add_subparsers command. It gives information on which subparsers is being invoked.

How can I get an argument name from argparse?

This is my command line script
import argparse
parser = argparse.ArgumentParser('My command line app')
parser.add_argument('--start', type=start, metavar='HOST', dest='result', nargs='*', default='all', help='Start hosts')
parser.add_argument('--stop', type=stop, metavar='HOST', dest='result', nargs='*', default='all', help='Stop hosts')
parser.add_argument('--status', type=status, metavar='HOST', dest='result', nargs='*', default='all', help='Show hosts status')
args = parser.parse_args()
Currently I defined one function for each option, but I would like to wrap them in only one for these three options. Then I would need to know which argument was used. Is it possible with argparse?
Solution
At the end I took this way:
import argparse
def wrapper(command, hosts):
pass
parser = argparse.ArgumentParser('My script')
parser.add_argument('action', choices=['start', 'stop', 'status'], help='Action')
parser.add_argument('hosts', metavar='HOST', nargs='*', default='all')
args = parser.parse_args()
wrapper(args.action, args.hosts)

It sounds like the saner way to handle this would be the choices parameter:
commands = {'start': start, 'stop': stop, 'status': status}
parser = argparse.ArgumentParser('My command line app')
parser.add_argument('command', choices=commands.keys())
parser.add_argument('hosts', nargs='*', default=[])
args = parser.parse_args()
commands[args.command](*args.hosts)

Take multiple patterns from cli. argparse Python3

I have a python version of grep, that I am building for an assignment. I want my python module to take multiple patterns from the command line, just like grep. However no matter what I do, I keep getting conflicts with my 'debug' argument.
This is what it currently looks like from command line (with -h):
pgreper.py [-h] [--debug] pattern
At the moment I can only search with one pattern:
cat input.txt | ./pgreper.py "were"
I would like to be able to search the input.txt file like so, with multiple patterns:
cat input.txt | ./pgreper.py "were" "you"
However when I try and do this, I get the following error:
pgreper.py: error: unrecognized argument: you
I know that it is related to the fact I generate a pattern to search by reading sys.argv[1]. How would I go about editing my script, to allow it to take multiple patterns from sys.argv, without affecting the optional arguments I have implemented?
Many thanks :)
ps Please ignore my comments, thanks.
#!/usr/bin/python3
import sys
import re
import time
import datetime
import inspect
import argparse
parser = argparse.ArgumentParser(description='Python Grep.')
parser.add_argument('--debug', default='debug', action='store_true', help='Print debug messages')
parser.add_argument('pattern', type=str, help='Pattern for pgrepping')
args = parser.parse_args()
class CodeTrace(object):
def __init__(self, line, pattern):
self.line = line
self.pattern = pattern
# #staticmethod
def trace(self, line, pattern):
# Creating Timestamp
ts = time.time()
# Formatting Timestamp
ts = datetime.datetime.fromtimestamp(ts).strftime('[%Y-%m-%d %H:%M:%S:%f]')
stack = inspect.stack()
# Retrieve calling class information
the_class = stack[1][0].f_locals["self"].__class__
# Retrieve calling method information
the_method = stack[1][0].f_code.co_name
the_variables = stack[1][0].f_code.co_varnames
# Formats the contents of the debug trace into a readable format,
# Any parameters passed to the method and the return value, are included in the debug trace
debug_trace = ("{} {}.{}.{} {} {} ".format(ts, str(the_class), the_method, the_variables, pattern, line))
# Send out the debug trace as a standard error output
sys.stderr.write(debug_trace + "\n")
class Grepper(object):
def __init__(self, pattern):
self.pattern = pattern
# #CodeTrace.trace()
def matchline(self, pattern):
regex = re.compile(self.pattern)
for line in sys.stdin:
if regex.search(line):
sys.stdout.write(line)
if args.debug != 'debug':
(CodeTrace(line, pattern).trace(line, pattern))
def main():
pattern = str(sys.argv[1])
print(sys.argv)
Grepper(pattern).matchline(pattern)
if __name__ == "__main__":
main()

You can tell argparse to expect 1 or more arguments, using the nargs keyword argument:
parser.add_argument('patterns', type=str, nargs='+', help='Pattern(s) for pgrepping')
Here + means 1 or more. You can then combine these patterns:
pattern = '|'.join(['(?:{})'.format(p) for p in args.patterns])
and pass that to your grepper. The patterns are combined with | after first being placed in a non-capturing group ((?:...)) to make sure each pattern is treated as distinct.
I'd place all argument parsing in the main() function here:
def main():
parser = argparse.ArgumentParser(description='Python Grep.')
parser.add_argument('--debug', action='store_true', help='Print debug messages')
parser.add_argument('pattern', type=str, nargs='+', help='Pattern(s) for pgrepping')
args = parser.parse_args()
pattern = '|'.join(['(?:{})'.format(p) for p in args.pattern])
Grepper(pattern, args.debug).matchline()
I also removed the default for the --debug option; using store_true means it'll default to False; you can then simply test for args.debug being true or not.
You don't need to pass in pattern twice to Grepper(); you can simply use self.pattern in the matchline method, throughout. Instead, I'd pass in args.debug to Grepper() as well (no need for it to be a global).
Quick demo of what the argument parsing look like, including the help message:
>>> import argparse
>>> parser = argparse.ArgumentParser(description='Python Grep.')
>>> parser.add_argument('--debug', action='store_true', help='Print debug messages')
_StoreTrueAction(option_strings=['--debug'], dest='debug', nargs=0, const=True, default=False, type=None, choices=None, help='Print debug messages', metavar=None)
>>> parser.add_argument('pattern', type=str, nargs='+', help='Pattern(s) for pgrepping')
_StoreAction(option_strings=[], dest='pattern', nargs='+', const=None, default=None, type=<type 'str'>, choices=None, help='Pattern(s) for pgrepping', metavar=None)
>>> parser.print_help()
usage: [-h] [--debug] pattern [pattern ...]
Python Grep.
positional arguments:
pattern Pattern(s) for pgrepping
optional arguments:
-h, --help show this help message and exit
--debug Print debug messages
>>> parser.parse_args(['where'])
Namespace(debug=False, pattern=['where'])
>>> parser.parse_args(['were'])
Namespace(debug=False, pattern=['were'])
>>> parser.parse_args(['were', 'you'])
Namespace(debug=False, pattern=['were', 'you'])
>>> parser.parse_args(['--debug', 'were', 'you'])
Namespace(debug=True, pattern=['were', 'you'])
The pattern then looks like this:
>>> args = parser.parse_args(['were', 'you'])
>>> args.pattern
['were', 'you']
>>> pattern = '|'.join(['(?:{})'.format(p) for p in args.pattern])
>>> pattern
'(?:were)|(?:you)'
If instead you wanted all patterns to match, you'll need to alter Grepper() to take multiple patterns and test all those patterns. Use the all() function to make that efficient (only test as many patterns as is required):
def main():
parser = argparse.ArgumentParser(description='Python Grep.')
parser.add_argument('--debug', action='store_true', help='Print debug messages')
parser.add_argument('pattern', type=str, nargs='+', help='Pattern(s) for pgrepping')
args = parser.parse_args()
Grepper(args.pattern, args.debug).matchline()
and the Grepper class becomes:
class Grepper(object):
def __init__(self, patterns, debug=False):
self.patterns = [re.compile(p) for p in patterns]
self.debug = debug
def matchline(self, debug):
for line in sys.stdin:
if all(p.search(line) for p in self.patterns):
sys.stdout.write(line)
if self.debug:
CodeTrace(line, self.patterns).trace(line)
with appropriate adjustments for the CodeTrace class.

Your argparse argument configuration were not correct. This is really now how you configure the argument. Check the Python documentation for argparse as there is a very good example in there.
the format should always be yourscript.py -aARGUMENTVAL -bARGUMENTVAL ...etc. the -a and -b styles are important.
Your code is edited to have a better application of argparse module below. See if this works better (without action argument for debug):
import sys
import re
import time
import datetime
import inspect
import argparse
parser = argparse.ArgumentParser(description='Python Grep.')
parser.add_argument('-p', '--pattern', type=str, help='Pattern for pgrepping')
parser.add_argument('-d','--debug', type=str, default="false", help='Print debug messages')
args = vars(parser.parse_args());
class CodeTrace(object):
def __init__(self, line, pattern):
self.line = line
self.pattern = pattern
# #staticmethod
def trace(self, line, pattern):
# Creating Timestamp
ts = time.time()
# Formatting Timestamp
ts = datetime.datetime.fromtimestamp(ts).strftime('[%Y-%m-%d %H:%M:%S:%f]')
stack = inspect.stack()
# Retrieve calling class information
the_class = stack[1][0].f_locals["self"].__class__
# Retrieve calling method information
the_method = stack[1][0].f_code.co_name
the_variables = stack[1][0].f_code.co_varnames
# Formats the contents of the debug trace into a readable format,
# Any parameters passed to the method and the return value, are included in the debug trace
debug_trace = ("{} {}.{}.{} {} {} ".format(ts, str(the_class), the_method, the_variables, pattern, line))
# Send out the debug trace as a standard error output
sys.stderr.write(debug_trace + "\n")
class Grepper(object):
def __init__(self, pattern):
self.pattern = pattern
# #CodeTrace.trace()
def matchline(self, pattern):
regex = re.compile(self.pattern)
for line in sys.stdin:
if regex.search(line):
sys.stdout.write(line)
if args.debug != 'debug':
(CodeTrace(line, pattern).trace(line, pattern))
def main():
pattern = str(args['pattern'])
print(sys.argv)
Grepper(pattern).matchline(pattern)
if __name__ == "__main__":
main()
You can supply comma delimited string to separate patters `-p"were,you". Use python's powerful string functions for that
pattern = ((args['pattern']).replace(" ", "")).split(",");
the above will give you a list of patterns to look for?