pass json file as command line argument through parser , is this possible?

I need to overwrite json file parameters to a python dictionary through command line argument parser. Since, json file is located in the current working directory but its name can be dynamic , so i want something like below :-

python python_script --infile json_file

python_script:

if __name__ == "__main__":
   profileInfo = dict()
   profileInfo['profile'] = "enterprisemixed"
   profileInfo['nodesPerLan'] = 50

json_file:

{
   "profile":"adhoc",               
   "nodesPerLan" : 4
}

I tried to add the following lines, but don't know how to load this json data to the python dictionary :-

import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--infile', nargs = 1, help="JSON file to be processed",type=argparse.FileType('r'))
arguments = parser.parse_args()