How can I pass a list as a command-line argument with argparse?

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I am trying to pass a list as an argument to a command line program. Is there an argparse option to pass a list as option?

parser.add_argument('-l', '--list',
                      type=list, action='store',
                      dest='list',
                      help='<Required> Set flag',
                      required=True)

Script is called like below

python test.py -l "265340 268738 270774 270817"

How can I pass a list as a command-line argument with argparse , This will inspect the command line, convert each argument to the appropriate parents - A list of ArgumentParser objects whose arguments should also be included Generally, argument defaults are specified either by passing a default to  I am trying to pass a list as an argument to a command line program. Is there an argparse option to pass a list as option? parser.add_argument('-l', '--list', type=list, action='store', dest='list', help='<Required> Set flag', required=True) The script is called like below. python test.py -l "265340 268738 270774 270817"


I prefer passing a delimited string which I parse later in the script. The reasons for this are; the list can be of any type int or str, and sometimes using nargs I run into problems if there are multiple optional arguments and positional arguments.

parser = ArgumentParser()
parser.add_argument('-l', '--list', help='delimited list input', type=str)
args = parser.parse_args()
my_list = [int(item) for item in args.list.split(',')]

Then,

python test.py -l "265340,268738,270774,270817" [other arguments]

or,

python test.py -l 265340,268738,270774,270817 [other arguments]

will work fine. The delimiter can be a space, too, which would though enforce quotes around the argument value like in the example in the question.

15.4. argparse, This assigns a list of values to a flag that is used when executing the Python program from the command line. Use argparse.ArgumentParser.add_argument() to  These information tell ArgumentParser how to take arguments from the command-line and turn them into objects. Syntax: ArgumentParser.add_argument(name or flags…[, action][, nargs][, const][, default][, type][, choices][, required][, help][, metavar][, dest]) Parameters: name or flags– either a name or list of option string


Additionally to nargs, you might want to use choices if you know the list in advance:

>>> parser = argparse.ArgumentParser(prog='game.py')
>>> parser.add_argument('move', choices=['rock', 'paper', 'scissors'])
>>> parser.parse_args(['rock'])
Namespace(move='rock')
>>> parser.parse_args(['fire'])
usage: game.py [-h] {rock,paper,scissors}
game.py: error: argument move: invalid choice: 'fire' (choose from 'rock',
'paper', 'scissors')

How to pass a list as an argument using argparse in Python, Command line arguments are those values that are passed during the calling of Usually, python uses sys.argv array to deal with such arguments but here we  Figure 2: Using the argparse Python package you can easily parse command line arguments in the terminal/command line. In this next example we’ll be counting shapes in any given input image while annotating an output image that gets written to disk.


Using nargs parameter in argparse's add_argument method

I use nargs='' as an add_argument parameter. I specifically used nargs='' to the option to pick defaults if I am not passing any explicit arguments

Including a code snippet as example:

Example: temp_args1.py

Please Note: The below sample code is written in python3. By changing the print statement format, can run in python2

#!/usr/local/bin/python3.6

from argparse import ArgumentParser

description = 'testing for passing multiple arguments and to get list of args'
parser = ArgumentParser(description=description)
parser.add_argument('-i', '--item', action='store', dest='alist',
                    type=str, nargs='*', default=['item1', 'item2', 'item3'],
                    help="Examples: -i item1 item2, -i item3")
opts = parser.parse_args()

print("List of items: {}".format(opts.alist))

Note: I am collecting multiple string arguments that gets stored in the list - opts.alist If you want list of integers, change the type parameter on parser.add_argument to int

Execution Result:

python3.6 temp_agrs1.py -i item5 item6 item7
List of items: ['item5', 'item6', 'item7']

python3.6 temp_agrs1.py -i item10
List of items: ['item10']

python3.6 temp_agrs1.py
List of items: ['item1', 'item2', 'item3']

Command-Line Option and Argument Parsing using argparse in , By default, the arguments are taken from sys.argv[1:], but you can also pass your own list. The options are processed using the GNU/POSIX syntax, so option and​  Once all of the arguments are defined, you can parse the command line by passing a sequence of argument strings to parse_args (). By default, the arguments are taken from sys.argv [1:], but you can also pass your own list. The options are processed using the GNU/POSIX syntax, so option and argument values can be mixed in the sequence.


If you are intending to make a single switch take multiple parameters, then you use nargs='+'. If your example '-l' is actually taking integers:

a = argparse.ArgumentParser()
a.add_argument(
    '-l', '--list',  # either of this switches
    nargs='+',       # one or more parameters to this switch
    type=int,        # /parameters/ are ints
    dest='list',     # store in 'list'.
    default=[],      # since we're not specifying required.
)

print a.parse_args("-l 123 234 345 456".split(' '))
print a.parse_args("-l 123 -l=234 -l345 --list 456".split(' '))

Produces

Namespace(list=[123, 234, 345, 456])
Namespace(list=[456])  # Attention!

If you specify the same argument multiple times, the default action ('store') replaces the existing data.

The alternative is to use the append action:

a = argparse.ArgumentParser()
a.add_argument(
    '-l', '--list',  # either of this switches
    type=int,        # /parameters/ are ints
    dest='list',     # store in 'list'.
    default=[],      # since we're not specifying required.
    action='append', # add to the list instead of replacing it
)

print a.parse_args("-l 123 -l=234 -l345 --list 456".split(' '))

Which produces

Namespace(list=[123, 234, 345, 456])

Or you can write a custom handler/action to parse comma-separated values so that you could do

-l 123,234,345 -l 456

argparse – Command line option and argument parsing., argv array that contains all of the command-line parameters. The first element in sys.argv is the script itself. So a parameter passed in will be in  Yes, certainly argparse can be used to pass arguments both from command line and from code.. For example: import argparse # Define default values parser = argparse.ArgumentParser() parser.add_argument('--foo', default=1, type=float, help='foo') # Get the args container with default values if __name__ == '__main__': args = parser.parse_args() # get arguments from command line else: args


Python Argparse Cookbook – mkaz.blog, Use sys.argv and argparse module to parse command-line arguments. If you want to pass command-line arguments to a python program, go to “Run > Edit We can read the command-line arguments from this list and use it in our program. parser.add_argument('-u', '--username', help='The Username for authentication.') Each option only populates one value in args, so you shouldn't try to unpack two. Try this instead: username = args.username Values are separated on the command line by spaces, not commas, so use this:--hostlist 192.168.1.1 192.168.1.2


Python Command Line Arguments, Using sys.argv; Using getopt; Using argparse If you do not pass any argument to the rm command, you will get an error like so - args is the list of arguments taken from the command-line. shortopts is where you specify the  Having spaces around --is important, this is a signal that Blender should stop parsing the arguments and allows you to pass your own arguments to Python. Further information: For a more comprehensive script example, background_job.py is a Python template which comes with Blender, this uses Python's argparse module, for more flexible handling of


Argument Parsing in Python, An argument is a single part of a command line, delimited by blanks. ArgumentParser(description='List the content of a folder') # Add the arguments In this case, argparse doesn't know if you want to pass the value 42 to the --input​  Sometimes, for example when dealing with a particularly long argument lists, it may make sense to keep the list of arguments in a file rather than typing it out at the command line. If the fromfile_prefix_chars= argument is given to the ArgumentParser constructor, then arguments that start with any of the specified characters will be treated as files, and will be replaced by the arguments they contain.