How to append data into a json key using python

November 30, 2021

I need to add data into the documents key within a json file with the structure below

{
  "inputDocuments": {
    "gcsDocuments": {
      "documents": [
        {
          "gcsUri": "gs://test/.PDF",
          "mimeType": "application/pdf"
        }
      ]
    }
  },
  "documentOutputConfig": {
    "gcsOutputConfig": {
      "gcsUri": "gs://test"
    }
  },
  "skipHumanReview": false

The final output should be something like

{
      "inputDocuments": {
        "gcsDocuments": {
          "documents": [
            {
              "gcsUri": "gs://test/FFL.PDF",
              "mimeType": "application/pdf"
            },
            {
              "gcsUri": "gs://test/BGF.PDF",
              "mimeType": "application/pdf"
            }
          ]
        }
      },
      "documentOutputConfig": {
        "gcsOutputConfig": {
          "gcsUri": "gs://test"
        }
      },
      "skipHumanReview": false

I have tried out to create a script using the code below, however I am getting a Keyerror while trying to add data and its not appending the data in the right format

# Python program to update
# JSON
import json

# function to add to JSON
def write_json(new_data, filename='keyvalue.json'):
    with open(filename,'r+') as file:
        # First we load existing data into a dict.
        file_data = json.load(file)
        # Join new_data with file_data inside emp_details
        file_data["documents"].append(new_data)
        # Sets file's current position at offset.
        file.seek(0)
        # convert back to json.
        json.dump(file_data, file, indent = 4)

    # python object to be appended
y = {
          "gcsUri": "gs://test/.PDF",
          "mimeType": "application/pdf"        
    }
    
write_json(y)