How to extract value of a key from an object of arrays in python

April 23, 2022

This might be a real noob question.

Thanks for helping.

I am receiving a json payload with the below structure

 {
    "response": true,
    "error": null,
    "msg": null,
    "data": {
        "slots": {
            "04/26/2022": [
                {
                    "0": 1650958200000,
                    "1": 19800,
                    "3": "1:00 PM",
                    "4": "26/Apr/2022 13:00 IST"
                },
                {
                    "0": 1650960000000,
                    "1": 19800,
                    "3": "1:30 PM",
                    "4": "26/Apr/2022 13:30 IST"
                },
                {
                    "0": 1650963600000,
                    "1": 19800,
                    "3": "2:30 PM",
                    "4": "26/Apr/2022 14:30 IST"
                },
                {
                    "0": 1650965400000,
                    "1": 19800,
                    "3": "3:00 PM",
                    "4": "26/Apr/2022 15:00 IST"
                },
                {
                    "0": 1650967200000,
                    "1": 19800,
                    "3": "3:30 PM",
                    "4": "26/Apr/2022 15:30 IST"
                }
            ],
            "04/24/2022": [],
            "04/25/2022": [],
            "04/23/2022": []
        }
    }
}

I want to create a new object with an array of the values of "0". Output should be

{
 "slots": [
          1650958200000,
          1650960000000,
          1650963600000,
          1650965400000,
          1650967200000
          ]
}

How would i go about doing this?

>Solution :

Here’s a straight-forward approach:

slots = payload["data"]["slots"]  # Assumes payload has been converted from JSON to Python

slots_obj = {"slots": [d["0"] for _, lst in slots.items() for d in lst]}

Output:

{'slots': [1650958200000,
           1650960000000,
           1650963600000,
           1650965400000,
           1650967200000,
           16539137693178]}

If you haven’t already, use json.loads to convert the JSON to a Python dictionary:

import json

payload = json.loads(payload)

The solution above uses what’s known as a list comprehension. It is equivalent to a for loop, which may be easier to understand:

timestamps = []  # Initialize an empty list to accumulate the Unix timestamps

# Iterate over each date, array pair in the slots dictionary using slots.items()
for _, slot_array in slots.items():
    # Iterate over each inner dictionary
    for slot_dict in slot_array:
        # Grab the value at the "0" and append it to the timestamps accumulator
        timestamps.append(slot_dict["0"])

# Finally create the new object, a dictionary with one key, "slots"
slots_obj = {"slots": timestamps}