I would like to use argparse to parse boolean command-line arguments written as "--foo True" or "--foo False". For example:
my_program --my_boolean_flag False
However, the following test code does not do what I would like:
import argparse
parser = argparse.ArgumentParser(description="My parser")
parser.add_argument("--my_bool", type=bool)
cmd_line = ["--my_bool", "False"]
parsed_args = parser.parse(cmd_line)
Sadly, parsed_args.my_bool evaluates to True. This is the case even when I change cmd_line to be ["--my_bool", ""], which is surprising, since bool("") evalutates to False.
How can I get argparse to parse "False", "F", and their lower-case variants to be False?
I think a more canonical way to do this is via:
command --feature
and
command --no-feature
argparse supports this version nicely:
Python 3.9+:
parser.add_argument('--feature', action=argparse.BooleanOptionalAction)
Python < 3.9:
parser.add_argument('--feature', action='store_true')
parser.add_argument('--no-feature', dest='feature', action='store_false')
parser.set_defaults(feature=True)
Of course, if you really want the --arg <True|False> version, you could pass ast.literal_eval as the "type", or a user defined function ...
def t_or_f(arg):
ua = str(arg).upper()
if 'TRUE'.startswith(ua):
return True
elif 'FALSE'.startswith(ua):
return False
else:
pass #error condition maybe?
Yet another solution using the previous suggestions, but with the "correct" parse error from argparse:
def str2bool(v):
if isinstance(v, bool):
return v
if v.lower() in ('yes', 'true', 't', 'y', '1'):
return True
elif v.lower() in ('no', 'false', 'f', 'n', '0'):
return False
else:
raise argparse.ArgumentTypeError('Boolean value expected.')
This is very useful to make switches with default values; for instance
parser.add_argument("--nice", type=str2bool, nargs='?',
const=True, default=False,
help="Activate nice mode.")
allows me to use:
script --nice
script --nice <bool>
and still use a default value (specific to the user settings). One (indirectly related) downside with that approach is that the 'nargs' might catch a positional argument -- see this related question and this argparse bug report.
If you want to allow --feature and --no-feature at the same time (last one wins)
This allows users to make a shell alias with --feature, and overriding it with --no-feature.
Python 3.9 and above
parser.add_argument('--feature', default=True, action=argparse.BooleanOptionalAction)
Python 3.8 and below
I recommend mgilson's answer:
parser.add_argument('--feature', dest='feature', action='store_true')
parser.add_argument('--no-feature', dest='feature', action='store_false')
parser.set_defaults(feature=True)
If you DON'T want to allow --feature and --no-feature at the same time
You can use a mutually exclusive group:
feature_parser = parser.add_mutually_exclusive_group(required=False)
feature_parser.add_argument('--feature', dest='feature', action='store_true')
feature_parser.add_argument('--no-feature', dest='feature', action='store_false')
parser.set_defaults(feature=True)
You can use this helper if you are going to set many of them:
def add_bool_arg(parser, name, default=False):
group = parser.add_mutually_exclusive_group(required=False)
group.add_argument('--' + name, dest=name, action='store_true')
group.add_argument('--no-' + name, dest=name, action='store_false')
parser.set_defaults(**{name:default})
add_bool_arg(parser, 'useful-feature')
add_bool_arg(parser, 'even-more-useful-feature')
Here is another variation without extra row/s to set default values. The boolean value is always assigned, so that it can be used in logical statements without checking beforehand:
import argparse
parser = argparse.ArgumentParser(description="Parse bool")
parser.add_argument("--do-something", default=False, action="store_true",
help="Flag to do something")
args = parser.parse_args()
if args.do_something:
print("Do something")
else:
print("Don't do something")
print(f"Check that args.do_something={args.do_something} is always a bool.")
oneliner:
parser.add_argument('--is_debug', default=False, type=lambda x: (str(x).lower() == 'true'))
There seems to be some confusion as to what type=bool and type='bool' might mean. Should one (or both) mean 'run the function bool(), or 'return a boolean'? As it stands type='bool' means nothing. add_argument gives a 'bool' is not callable error, same as if you used type='foobar', or type='int'.
But argparse does have registry that lets you define keywords like this. It is mostly used for action, e.g. `action='store_true'. You can see the registered keywords with:
parser._registries
which displays a dictionary
{'action': {None: argparse._StoreAction,
'append': argparse._AppendAction,
'append_const': argparse._AppendConstAction,
...
'type': {None: <function argparse.identity>}}
There are lots of actions defined, but only one type, the default one, argparse.identity.
This code defines a 'bool' keyword:
def str2bool(v):
#susendberg's function
return v.lower() in ("yes", "true", "t", "1")
p = argparse.ArgumentParser()
p.register('type','bool',str2bool) # add type keyword to registries
p.add_argument('-b',type='bool') # do not use 'type=bool'
# p.add_argument('-b',type=str2bool) # works just as well
p.parse_args('-b false'.split())
Namespace(b=False)
parser.register() is not documented, but also not hidden. For the most part the programmer does not need to know about it because type and action take function and class values. There are lots of stackoverflow examples of defining custom values for both.
In case it isn't obvious from the previous discussion, bool() does not mean 'parse a string'. From the Python documentation:
bool(x): Convert a value to a Boolean, using the standard truth testing procedure.
Contrast this with
int(x): Convert a number or string x to an integer.
Simplest & most correct way is:
from distutils.util import strtobool
parser.add_argument('--feature', dest='feature',
type=lambda x: bool(strtobool(x)))
Do note that True values are y, yes, t, true, on and 1;
false values are n, no, f, false, off and 0. Raises ValueError if val is anything else.
A quite similar way is to use:
feature.add_argument('--feature',action='store_true')
and if you set the argument --feature in your command
command --feature
the argument will be True, if you do not set type --feature the arguments default is always False!
I was looking for the same issue, and imho the pretty solution is :
def str2bool(v):
return v.lower() in ("yes", "true", "t", "1")
and using that to parse the string to boolean as suggested above.
This works for everything I expect it to:
add_boolean_argument(parser, 'foo', default=True)
parser.parse_args([]) # Whatever the default was
parser.parse_args(['--foo']) # True
parser.parse_args(['--nofoo']) # False
parser.parse_args(['--foo=true']) # True
parser.parse_args(['--foo=false']) # False
parser.parse_args(['--foo', '--nofoo']) # Error
The code:
def _str_to_bool(s):
"""Convert string to bool (in argparse context)."""
if s.lower() not in ['true', 'false']:
raise ValueError('Need bool; got %r' % s)
return {'true': True, 'false': False}[s.lower()]
def add_boolean_argument(parser, name, default=False):
"""Add a boolean argument to an ArgumentParser instance."""
group = parser.add_mutually_exclusive_group()
group.add_argument(
'--' + name, nargs='?', default=default, const=True, type=_str_to_bool)
group.add_argument('--no' + name, dest=name, action='store_false')
Simplest. It's not flexible, but I prefer simplicity.
parser.add_argument('--boolean_flag',
help='This is a boolean flag.',
type=eval,
choices=[True, False],
default='True')
EDIT: If you don't trust the input, don't use eval.
In addition to what #mgilson said, it should be noted that there's also a ArgumentParser.add_mutually_exclusive_group(required=False) method that would make it trivial to enforce that --flag and --no-flag aren't used at the same time.
This is actually outdated. For Python 3.7+, Argparse now supports boolean args (search BooleanOptionalAction).
The implementation looks like this:
import argparse
ap = argparse.ArgumentParser()
# List of args
ap.add_argument('--foo', default=True, type=bool, help='Some helpful text that is not bar. Default = True')
# Importable object
args = ap.parse_args()
One other thing to mention: this will block all entries other than True and False for the argument via argparse.ArgumentTypeError. You can create a custom error class for this if you want to try to change this for any reason.
A simpler way would be to use as below.
parser.add_argument('--feature', type=lambda s: s.lower() in ['true', 't', 'yes', '1'])
After previously following #akash-desarda 's excellence answer https://stackoverflow.com/a/59579733/315112 , to use strtobool via lambda, later, I decide to use strtobool directly instead.
import argparse
from distutils import util
parser.add_argument('--feature', type=util.strtobool)
Yes you're right, strtobool is returning an int, not a bool. But strtobool will not returning any other value except 0 and 1, and python will get them converted to a bool value seamlessy and consistently.
>>> 0 == False
True
>>> 0 == True
False
>>> 1 == False
False
>>> 1 == True
True
While on receiving a wrong input value like
python yours.py --feature wrong_value
An argparse.Action with strtobool compared to lambda will produce a slightly clearer/comprehensible error message:
yours.py: error: argument --feature: invalid strtobool value: 'wrong_value'
Compared to this code,
parser.add_argument('--feature', type=lambda x: bool(util.strtobool(x))
Which will produce a less clear error message:
yours.py: error: argument --feature: invalid <lambda> value: 'wrong_value'
Simplest way would be to use choices:
parser = argparse.ArgumentParser()
parser.add_argument('--my-flag',choices=('True','False'))
args = parser.parse_args()
flag = args.my_flag == 'True'
print(flag)
Not passing --my-flag evaluates to False. The required=True option could be added if you always want the user to explicitly specify a choice.
As an improvement to #Akash Desarda 's answer, you could do
import argparse
from distutils.util import strtobool
parser = argparse.ArgumentParser()
parser.add_argument("--foo",
type=lambda x:bool(strtobool(x)),
nargs='?', const=True, default=False)
args = parser.parse_args()
print(args.foo)
And it supports python test.py --foo
(base) [costa#costa-pc code]$ python test.py
False
(base) [costa#costa-pc code]$ python test.py --foo
True
(base) [costa#costa-pc code]$ python test.py --foo True
True
(base) [costa#costa-pc code]$ python test.py --foo False
False
I think the most canonical way will be:
parser.add_argument('--ensure', nargs='*', default=None)
ENSURE = config.ensure is None
Expanding on gerardw's answer
The reason parser.add_argument("--my_bool", type=bool) doesn't work is that bool("mystring") is True for any non-empty string so bool("False") is actually True.
What you want is
my_program.py
import argparse
parser = argparse.ArgumentParser(description="My parser")
parser.add_argument(
"--my_bool",
choices=["False", "True"],
)
parsed_args = parser.parse_args()
my_bool = parsed_args.my_bool == "True"
print(my_bool)
$ python my_program.py --my_bool False
False
$ python my_program.py --my_bool True
True
$ python my_program.py --my_bool true
usage: my_program.py [-h] [--my_bool {False,True}]
my_program.py: error: argument --my_bool: invalid choice: 'true' (choose from 'False', 'True')
Quick and easy, but only for arguments 0 or 1:
parser.add_argument("mybool", default=True,type=lambda x: bool(int(x)))
myargs=parser.parse_args()
print(myargs.mybool)
The output will be "False" after calling from terminal:
python myscript.py 0
I found good way to store default value of parameter as False and when it is present in commandline argument then its value should be true.
cmd command
when you want argument to be true:
python main.py --csv
when you want your argument should be false:
python main.py
import argparse
from ast import parse
import sys
parser = argparse.ArgumentParser(description='')
parser.add_argument('--csv', action='store_true', default = False
,help='read from csv')
args = parser.parse_args()
if args.csv:
print('reading from csv')
class FlagAction(argparse.Action):
# From http://bugs.python.org/issue8538
def __init__(self, option_strings, dest, default=None,
required=False, help=None, metavar=None,
positive_prefixes=['--'], negative_prefixes=['--no-']):
self.positive_strings = set()
self.negative_strings = set()
for string in option_strings:
assert re.match(r'--[A-z]+', string)
suffix = string[2:]
for positive_prefix in positive_prefixes:
self.positive_strings.add(positive_prefix + suffix)
for negative_prefix in negative_prefixes:
self.negative_strings.add(negative_prefix + suffix)
strings = list(self.positive_strings | self.negative_strings)
super(FlagAction, self).__init__(option_strings=strings, dest=dest,
nargs=0, const=None, default=default, type=bool, choices=None,
required=required, help=help, metavar=metavar)
def __call__(self, parser, namespace, values, option_string=None):
if option_string in self.positive_strings:
setattr(namespace, self.dest, True)
else:
setattr(namespace, self.dest, False)
Similar to #Akash but here is another approach that I've used. It uses str than lambda because python lambda always gives me an alien-feelings.
import argparse
from distutils.util import strtobool
parser = argparse.ArgumentParser()
parser.add_argument("--my_bool", type=str, default="False")
args = parser.parse_args()
if bool(strtobool(args.my_bool)) is True:
print("OK")
just do the following , you can make --test = True by using
python filename --test
parser.add_argument("--test" , default=False ,help="test ?", dest='test', action='store_true')
Convert the value:
def __arg_to_bool__(arg):
"""__arg_to_bool__
Convert string / int arg to bool
:param arg: argument to be converted
:type arg: str or int
:return: converted arg
:rtype: bool
"""
str_true_values = (
'1',
'ENABLED',
'ON',
'TRUE',
'YES',
)
str_false_values = (
'0',
'DISABLED',
'OFF',
'FALSE',
'NO',
)
if isinstance(arg, str):
arg = arg.upper()
if arg in str_true_values:
return True
elif arg in str_false_values:
return False
if isinstance(arg, int):
if arg == 1:
return True
elif arg == 0:
return False
if isinstance(arg, bool):
return arg
# if any other value not covered above, consider argument as False
# or you could just raise and error
return False
[...]
args = ap.parse_args()
my_arg = options.my_arg
my_arg = __arg_to_bool__(my_arg)
You can create a BoolAction and then use it
class BoolAction(Action):
def __init__(
self,
option_strings,
dest,
nargs=None,
default: bool = False,
**kwargs,
):
if nargs is not None:
raise ValueError('nargs not allowed')
super().__init__(option_strings, dest, default=default, **kwargs)
def __call__(self, parser, namespace, values, option_string=None):
input_value = values.lower()
b = input_value in ['true', 'yes', '1']
if not b and input_value not in ['false', 'no', '0']:
raise ValueError('Invalid boolean value "%s".)
setattr(namespace, self.dest, b)
and then set action=BoolAction in parser.add_argument()
I've got some Python argparse command-line processing code that initially looked like this:
import argparse
ap = argparse.ArgumentParser()
ap.add_argument("--x", help = "Set `x`.", action = "store_true", default = False)
ap.add_argument("--y", help = "Set `y`.", action = "store_true", default = False)
ap.add_argument(
"--all", help = "Equivalent to `--x --y`.",
action = "store_true", default = False
)
args = ap.parse_args()
if args.all:
args.x = True
args.y = True
print "args.x", args.x
print "args.y", args.y
The basic idea: I have some boolean flags that toggle on a particular setting (--x, --y, etc), and I want to add a convenience option that toggles multiple settings on - e.g. --all is equivalent to --x --y.
I wanted to avoid having any command-line processing logic that was not contained within the ArgumentParser and done in parse_args, so I came up with this solution using custom argparse.Actions:
import argparse
def store_const_multiple(const, *destinations):
"""Returns an `argparse.Action` class that sets multiple argument
destinations (`destinations`) to `const`."""
class store_const_multiple_action(argparse.Action):
def __init__(self, *args, **kwargs):
super(store_const_multiple_action, self).__init__(
metavar = None, nargs = 0, const = const, *args, **kwargs
)
def __call__(self, parser, namespace, values, option_string = None):
for destination in destinations:
setattr(namespace, destination, const)
return store_const_multiple_action
def store_true_multiple(*destinations):
"""Returns an `argparse.Action` class that sets multiple argument
destinations (`destinations`) to `True`."""
return store_const_multiple(True, *destinations)
ap = argparse.ArgumentParser()
ap.add_argument("--x", help = "Set `x`.", action = "store_true", default = False)
ap.add_argument("--y", help = "Set `y`.", action = "store_true", default = False)
ap.add_argument(
"--all", help = "Equivalent to `--x --y`.",
action = store_true_multiple("x", "y")
)
args = ap.parse_args()
print "args.x", args.x
print "args.y", args.y
Is there any clean way of achieving what I want with argparse without either (0) doing some processing after parse_args() (first example) or (2) writing a custom argparse.Action (second example)?
This is late, and not exactly what you wanted, but here is something you could try:
import argparse
myflags = ['x', 'y', 'z']
parser = argparse.ArgumentParser()
parser.add_argument('--flags', nargs="+", choices=myflags)
parser.add_argument('--all-flags', action='store_const', const=myflags, dest='flags')
args = parser.parse_args()
print(args)
Then calling python myscript.py --flags x y outputs this
Namespace(flags=['x', 'y'])
And calling python myscript.py --all-flags outputs this
Namespace(flags=['x', 'y', 'z'])
But you'll have to check your flags via 'x' in args.flags instead of simply args.x
I have a functions like this
def add(x,y):
print x+y
def square(a):
print a**2
Now I am defining linux commands(options) for this functions using argparse.
I tried with this code
import argparse
# Create Parser and Subparser
parser = argparse.ArgumentParser(description="Example ArgumentParser")
subparser = parser.add_subparsers(help="commands")
# Make Subparsers
add_parser = subparser.add_parser('--add', help="add func")
add_parser.add_argument("x",type=float,help='first number')
add_parser.add_argument("y",type=float,help='second number')
add_parser.set_defaults(func='add')
square_parser = subparser.add_parser('--square', help="square func")
square_parser.add_argument("a",type=float,help='number to square')
square_parser.set_defaults(func='square')
args = parser.parse_args()
def add(x,y):
print x + y
def square(a):
print a**2
if args.func == '--add':
add(args.x,args.y)
if args.func == '--square':
square(args.a)
But I am getting error while passing command as python code.py --add 2 3
invalid choice: '2' (choose from '--add', '--square')
--add is the form of an optionals flag, add is the correct form for a subparser name
import argparse
# Create Parser and Subparser
parser = argparse.ArgumentParser(description="Example ArgumentParser")
subparser = parser.add_subparsers(dest='cmd', help="commands")
# Make Subparsers
add_parser = subparser.add_parser('add', help="add func")
add_parser.add_argument("x",type=float,help='first number')
add_parser.add_argument("y",type=float,help='second number')
add_parser.set_defaults(func='add')
square_parser = subparser.add_parser('square', help="square func")
square_parser.add_argument("a",type=float,help='number to square')
square_parser.set_defaults(func='square')
args = parser.parse_args()
print(args)
def add(x,y):
print x + y
def square(a):
print a**2
if args.func == 'add': # if args.cmd=='add': also works
add(args.x,args.y)
if args.func == 'square':
square(args.a)
producing
0950:~/mypy$ python stack43557510.py add 2 3
Namespace(cmd='add', func='add', x=2.0, y=3.0)
5.0
I added dest='cmd' to the add_subparsers command, and print(args) to give more information. Note that the subparser name is now available as args.cmd. So you don't need the added func.
However the argparse docs do suggest an alternative use of set_defaults
https://docs.python.org/3/library/argparse.html#sub-commands
add_parser.set_defaults(func=add)
With this args.func is actually a function object, not just a string name. So it can be used as
args.func(args)
Note that I had to change how the functions handle their parameters:
def add(args):
print(args.x + args.y)
def square(args):
print(args.a**2)
# Create Parser and Subparser
parser = argparse.ArgumentParser(description="Example ArgumentParser")
subparser = parser.add_subparsers(dest='cmd', help="commands")
# Make Subparsers
add_parser = subparser.add_parser('add', help="add func")
add_parser.add_argument("x",type=float,help='first number')
add_parser.add_argument("y",type=float,help='second number')
add_parser.set_defaults(func=add)
square_parser = subparser.add_parser('square', help="square func")
square_parser.add_argument("a",type=float,help='number to square')
square_parser.set_defaults(func=square)
args = parser.parse_args()
print(args)
args.func(args)
producing
1001:~/mypy$ python stack43557510.py add 2 3
Namespace(cmd='add', func=<function add at 0xb73fd224>, x=2.0, y=3.0)
5.0
I have the following test-code
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--verbose", default = 0, type=int)
subparsers = parser.add_subparsers(dest = "parser_name")
parser_lan = subparsers.add_parser('car')
parser_lan.add_argument("--boo")
parser_lan.add_argument("--foo")
parser_serial = subparsers.add_parser('bus')
parser_serial.add_argument("--fun")
print parser.parse_args()
which defines two sub-parsers, having a different set of arguments. When I call the testcode as
tester.py --verbose 3 car --boo 1 --foo 2
I get the expected result
Namespace(boo='1', foo='2', parser_name='car', verbose=3)
What I want to have instead is the values from each subparser in a separate namespace or dict, something like
Namespace(subparseargs={boo:'1', foo:'2'}, parser_name='car', verbose=3)
so that the arguments from each subparser are logical separated from the arguments from the main parser (as verbose in this example).
How can I achieve this, with the arguments for each subparser in the same namespace (subparseargs in the example).
You need to go into the bowels of argparse a bit but changing your script to the following should do the trick:
import argparse
from argparse import _HelpAction, _SubParsersAction
class MyArgumentParser(argparse.ArgumentParser):
def parse_args(self, *args, **kw):
res = argparse.ArgumentParser.parse_args(self, *args, **kw)
from argparse import _HelpAction, _SubParsersAction
for x in parser._subparsers._actions:
if not isinstance(x, _SubParsersAction):
continue
v = x.choices[res.parser_name] # select the subparser name
subparseargs = {}
for x1 in v._optionals._actions: # loop over the actions
if isinstance(x1, _HelpAction): # skip help
continue
n = x1.dest
if hasattr(res, n): # pop the argument
subparseargs[n] = getattr(res, n)
delattr(res, n)
res.subparseargs = subparseargs
return res
parser = MyArgumentParser()
parser.add_argument("--verbose", default = 0, type=int)
subparsers = parser.add_subparsers(dest = "parser_name")
parser_lan = subparsers.add_parser('car')
parser_lan.add_argument("--boo")
parser_lan.add_argument("--foo")
parser_serial = subparsers.add_parser('bus')
parser_serial.add_argument("--fun")
print parser.parse_args()
I have started to develop a different approach (but similar to the suggestion by Anthon) and come up with a much shorter code. However, I am not sure my approach is a general solution for the problem.
To similar what Anthon is proposing, I define a new method which creates a list of 'top-level' arguments which are kept in args, while all the other arguments are returned as an additional dictionary:
class MyArgumentParser(argparse.ArgumentParser):
def parse_subargs(self, *args, **kw):
# parse as usual
args = argparse.ArgumentParser.parse_args(self, *args, **kw)
# extract the destination names for top-level arguments
topdest = [action.dest for action in parser._actions]
# loop over all arguments given in args
subargs = {}
for key, value in args.__dict__.items():
# if sub-parser argument found ...
if key not in topdest:
# ... remove from args and add to dictionary
delattr(args,key)
subargs[key] = value
return args, subargs
Comments on this approach welcome, especially any loopholes I overlooked.
Or manually, you could parse the args and create a dict with details:
# parse args
args = parser.parse_args()
args_dict = {}
for group in parser._action_groups:
# split into groups based on title
args_dict[group.title] = {}
for arg in group._group_actions:
if hasattr(args, arg.dest):
args_dict[group.title][arg.dest] = getattr(args, arg.dest)
# or args_dict[arg.dest] = getattr(args, arg.dest)
delattr(args, arg.dest)
# add remaining items into subparser options
args_dict["subparser"] |= vars(args)
return args_dict
I'm writing a relatively simple Python script which supports a couple of different commands. The different commands support different options and I want to be able to pass the options parsed by argparse to the correct method for the specified command.
The usage string looks like so:
usage: script.py [-h]
{a, b, c}
...
script.py: error: too few arguments
I can easily call the appropriate method:
def a():
...
def b():
...
def c():
...
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.set_defaults(method = a)
...
arguments = parser.parse_args()
arguments.method()
However, I have to pass arguments to these methods and they all accept different sets of arguments.
Currently, I just pass the Namespace object returned by argparse, like so:
def a(arguments):
arg1 = getattr(arguments, 'arg1', None)
...
This seems a little awkward, and makes the methods a little harder to reuse as I have to pass arguments as a dict or namespace rather than as usual parameters.
I would like someway of defining the methods with parameters (as you would a normal function) and still be able to call them dynamically while passing appropriate parameters. Like so:
def a(arg1, arg2):
...
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.set_defaults(method = a)
...
arguments = parser.parse_args()
arguments.method() # <<<< Arguments passed here somehow
Any ideas?
I found quite a nice solution:
import argparse
def a(arg1, arg2, **kwargs):
print arg1
print arg2
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.set_defaults(method = a)
parser.add_argument('arg1', type = str)
parser.add_argument('arg2', type = str)
arguments = parser.parse_args()
arguments.method(**vars(arguments))
Of course there's a minor problem if the arguments of the method clash with the names of the arguments argparse uses, though I think this is preferable to passing the Namespace object around and using getattr.
You're probably trying to achieve the functionality that sub-commands provide:
http://docs.python.org/dev/library/argparse.html#sub-commands
Not sure how practical this is, but by using inspect you can leave out the extraneous **kwargs parameter on your functions, like so:
import argparse
import inspect
def sleep(seconds=0):
print "sleeping", seconds, "seconds"
def foo(a, b=2, **kwargs):
print "a=",a
print "b=",b
print "kwargs=",kwargs
parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(title="subcommand")
parser_sleep = subparsers.add_parser('sleep')
parser_sleep.add_argument("seconds", type=int, default=0)
parser_sleep.set_defaults(func=sleep)
parser_foo = subparsers.add_parser('foo')
parser_foo.add_argument("-a", type=int, default=101)
parser_foo.add_argument("-b", type=int, default=201)
parser_foo.add_argument("--wacky", default=argparse.SUPPRESS)
parser_foo.set_defaults(func=foo)
args = parser.parse_args()
arg_spec = inspect.getargspec(args.func)
if arg_spec.keywords:
## convert args to a dictionary
args_for_func = vars(args)
else:
## get a subset of the dictionary containing just the arguments of func
args_for_func = {k:getattr(args, k) for k in arg_spec.args}
args.func(**args_for_func)
Examples:
$ python test.py sleep 23
sleeping 23 seconds
$ python test.py foo -a 333 -b 444
a= 333
b= 444
kwargs= {'func': <function foo at 0x10993dd70>}
$ python test.py foo -a 333 -b 444 --wacky "this is wacky"
a= 333
b= 444
kwargs= {'func': <function foo at 0x10a321d70>, 'wacky': 'this is wacky'}
Have fun!