Store Python function in JSON

Question

Say I have a JSON file as such:

{
  \"x\":5,
  \"y\":4,
  \"func\" : def multiplier(a,b):
               return a*d
}

This over-simplif

Answer 1

If you really need to store a function in an external JSON file, one solution could be to store a lambda function as a value and use the eval function to evaluate it from your script.

But be aware that using eval in your code could be dangerous, please consider the security implications before using it (see this article from realpython.com).

config.json

{
  "x": 5,
  "y": 4,
  "function": "lambda x, y : x * y"
}

Your Python file (test.py)

import json


def run():
    """Run function from JSON config."""

    with open("config.json") as f:
        data = json.load(f)

    x, y = data["x"], data["y"]
    multiplier = eval(data["function"])
    return multiplier(x, y)


if __name__ == "__main__":
   result = run()
   print(result)

Demo

In[2]: ls
test.py
config.json

In[3]: import json

In[4]: def run():
  ...:     """Run function from JSON config."""
  ...: 
  ...:     with open("config.json") as f:
  ...:         data = json.load(f)
  ...: 
  ...:     x, y = data["x"], data["y"]
  ...:     multiplier = eval(data["func"])
  ...:     return(multiplier(x, y))
  ...:    

In[5]: run()
20