Using argparse with function that takes **kwargs argument
I'm using argparse to take input and pass it to a function that takes as arguments two variables and **kwargs.
Here's my function:
import requests
import sys
import argparse
def location_by_coordinate(LAT, LNG, **kwargs):
if not kwargs:
coordinate_url = "https://api.instagram.com/v1/locations/search?lat=%s&lng=%s&access_token=%s" % (LAT, LNG, current_token)
r = requests.get(coordinate_url).text
else:
coordinate_url = "https://api.instagram.com/v1/locations/search?lat=%s&lng=%s&access_token=%s" % (LAT, LNG, current_token)
for key, value in kwargs.iteritems():
if 'DISTANCE' in kwargs:
distance = kwargs.get('DISTANCE')
if distance > 5000:
print distance
print "max distance is 5000m, value is reassigned to default of 1000m"
distance = 1000
coordinate_url = "https://api.instagram.com/v1/locations/search?lat=%s&lng=%s&access_token=%s" % (LAT, LNG, current_token)
r = requests.get(coordinate_url).text
else:
pass
coordinate_url = "https://api.instagram.com/v1/locations/search?lat=%s&lng=%s&access_token=%s" % (LAT, LNG, current_token)
r = requests.get(coordinate_url).text
if 'FACEBOOK_PLACES_ID' in kwargs:
fb_places_id = kwargs.get('FACEBOOK_PLACES_ID')
payload = {'FACEBOOK_PLACES_ID': '%s' % (fb_places_id), 'DISTANCE': '%s' % (DISTANCE)}
r = requests.get(coordinate_url, params=payload).text
if 'FOURSQUARE_ID' in kwargs:
foursquare_id = kwargs.get('FOURSQUARE_ID')
payload = {'FOURSQUARE_ID': '%s' % (foursquare_id), 'DISTANCE': '%s' % (DISTANCE)}
r = requests.get(coordinate_url, params=payload).text
if 'FOURSQUARE_V2_ID' in kwargs:
foursquare_v2_id = kwargs.get('FOURSQUARE_V2_ID')
payload = {'FOURSQUARE_V2_ID': '%s' % (foursquare_v2_id), 'DISTANCE': '%s' % (DISTANCE)}
r = requests.get(coordinate_url, params=payload).text
#print r
return r
Given this function and its use of **kwargs, how should I setup the subparsers?
Here's how I've setup the command line parser thus far:
def main():
parser = argparse.ArgumentParser(description="API Endpoints tester")
subparsers = parser.add_subparsers(dest="command", help="Available commands")
location_by_parser = subparsers.add_parser("location_by_coordinate", help="location function")
location_by_parser.add_argument("LAT", help="latitude")
location_by_parser.add_argument("LNG", help="longitude")
arguments = parser.parse_args(sys.argv[1:])
arguments = vars(arguments)
command = arguments.pop("command")
if command == "location_by_coordinate":
LAT, LNG = location_by_coordinate(**arguments)
else:
print "No command provided..."
if __name__ == "__main__":
main()
Obviously, the above main() function works fine with the location_by_coordinate() function when I call it at the command line like this:
$ python argstest.py location_by_coordinate 40.5949799 -73.9495148
But with the code the way it is currently, if I try:
$ python argstest.py location_by_coordinate 40.5949799 -73.9495148 DISTANCE=3000
Obviously, I get:
argstest.py: error: unrecognized arguments: DISTANCE=3000
But I'm not sure how to setup a subparser for **kwargs. If I try to setup a subparser like this:
location_by_parser.add_argument("**kwargs", help="**kwargs")
and then try that command again:
$ python argstest.py location_by_coordinate 40.5949799 -73.9495148 DISTANCE=3000
That doesn't work because the arguments object (which is a dictionary), becomes this:
{'LAT': '40.5949799', 'LNG': '-73.9495148', 'command': 'location_by_coordinate', '**kwargs': 'DISTANCE=3000'}
And this Traceback is returned:
Traceback (most recent call last):
File "argstest.py", line 118, in <module>
main()
File "argstest.py", line 108, in main
foo = location_by_coordinate(**arguments)
File "argstest.py", line 40, in location_by_coordinate
return r
UnboundLocalError: local variable 'r' referenced before assignment
How can I enable argparse to handle/to parse what is entered at the command line that is intended to be passed to the function via **kwargs?
Answer
Do you understand what is going on with the
{'LAT': '40.5949799', 'LNG': '-73.9495148', 'command': 'location_by_coordinate', '**kwargs': 'DISTANCE=3000'}
arguments dictionary? You defined a 'positional' argument with the name ('dest') of '**kwargs'. You could just as well named it 'foobar'. The parser assigned the string 'DISTANCE=3000' to that attribute in the args namespace, which turned into a dictionary key:value pair in arguments.
You could, of course, look for arguments['**kwargs'], and parse the value for yourself:
v = arguments['**kwargs'] # or pop if you prefer
if v is not None:
k, v = v.split('=')
arguments[k] = int(v)
It could be generalized to handle multiple pairs (defined with `nargs='*').
argparse does not handle arguments the same way as Python functions, so there's nothing exactly analogous the **kwargs.
The normal way to accept something like distance is with 'optionals' or flagged arguments.
parser.add_argument('-d','--distance', type=int, help=...)
which will accept
python argstest.py location_by_coordinate 40.5949799 -73.9495148 --distance=3000
python argstest.py location_by_coordinate 40.5949799 -73.9495148 --distance 3000
python argstest.py location_by_coordinate 40.5949799 -73.9495148 --d3000
python argstest.py location_by_coordinate 40.5949799 -73.9495148
It could also be setup to use --DISTANCE or other names. In the last case args namespace will have a default value for distance. The default default is None.
That's the straight forward way of adding kwarg like arguments to argparse.
Accepting arbitrary dictionary like pairs, distance:3000, distance=3000, has been asked before on SO. The answers have always been some variation of the parsing that I sketched above. It could be done in a custom Action class, or post parsing as I suggest.
oops, this answer is nearly a clone of one I wrote a few days ago: https://stackoverflow.com/a/33639147/901925
A similar 2011 question: Using argparse to parse arguments of form "arg= val"
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(edit)
Example with a function that takes *args:
In [2]: import argparse
In [3]: def foo(*args, **kwargs):
...: print('args',args)
...: print('kwargs',kwargs)
...:
In [4]: parser=argparse.ArgumentParser()
In [5]: parser.add_argument('arg1')
In [6]: parser.add_argument('arg2',nargs='+')
In [7]: args=parser.parse_args('one two three'.split())
In [8]: args
Out[8]: Namespace(arg1='one', arg2=['two', 'three'])
So I have 2 positional arguments, one with a single string value, the other with a list (due to the + nargs).
Call foo with these args attributes:
In [10]: foo(args.arg1)
args ('one',)
kwargs {}
In [11]: foo(args.arg1, args.arg2)
args ('one', ['two', 'three'])
kwargs {}
In [12]: foo(args.arg1, arg2=args.arg2)
args ('one',)
kwargs {'arg2': ['two', 'three']}
I defined 'positionals', but it would have worked just as well with 'optionals'. The distinction between positionals and optionals disappears in the namespace.
If I convert the namespace to a dictionary, I can pass values to foo in various ways, either through the *args or through **kwargs. It's all in how I call foo, not in how they appear in args or arguments. None of this is unique to argparse.
In [13]: arguments = vars(args)
In [14]: arguments
Out[14]: {'arg2': ['two', 'three'], 'arg1': 'one'}
In [15]: foo(arguments['arg2'], arguments['arg1'])
args (['two', 'three'], 'one')
kwargs {}
In [16]: foo(arguments['arg2'], arguments)
args (['two', 'three'], {'arg2': ['two', 'three'], 'arg1': 'one'})
kwargs {}
In [17]: foo(arguments['arg2'], **arguments)
args (['two', 'three'],)
kwargs {'arg2': ['two', 'three'], 'arg1': 'one'}
In [24]: foo(*arguments, **arguments)
args ('arg2', 'arg1') # *args is the keys of arguments
kwargs {'arg2': ['two', 'three'], 'arg1': 'one'}
In [25]: foo(*arguments.values(), **arguments)
args (['two', 'three'], 'one') # *args is the values of arguments
kwargs {'arg2': ['two', 'three'], 'arg1': 'one'}