Passing a JSON as a parameter from the run configuration in PyCharm

Passing the example parameter in the question is relatively straightforward. The only rule applying is that the quotes (") have to be escaped using backslashes (\"). For a more complicated example with more rules applying see Pycharm deletes quotation marks in paramenter field.

Run/Debug Configuration: Python

Configuration tab

When specifying the script parameters, follow these rules:

(...)

• If script parameter includes double quotes, escape the double quotes with backslashes,

So the example JSON string:

{"beam":5,"max_len_a":1.2,"max_len_b":10}

should be written as:

{\"beam\":5,\"max_len_a\":1.2,\"max_len_b\":10}

You can then easily convert the parameter to a JSON object using the script

import json
import sys

your_string = sys.argv[1]
z = json.loads(your_string)

The following screenshot shows the run configurations:

If you are using argparse and have an argument like this:

import argparse

parser = argparse.ArgumentParser(description='Demo-Tool')    
parser.add_argument('--params', type=str, help='JSON-serialized params dict')

You need to escape the quotes using backslashes and put quotes around the JSON. The following did the trick for me in the run configurations:

--params "{\"beam\":5,\"max_len_a\":1.2,\"max_len_b\":10}"