To write a json to a file, use the built-in json.dump(obj, file) method that serializes a Python object to a JSON-formatted file. It writes directly to an open file object.

import json

data = {
    "title": "HP and Half blood Prince",
    "author": "JK Rowling",
    "pages": 544,
    "genres": "fantasy",
    "rating": 4.7
}

with open('dir/data.json', 'w') as file:
    json.dump(data, file, indent=4)

print("Data written to file successfully.")

# Output: Data written to file successfully.

In this code, we directly open the file in write mode (‘w’) and dump the json data into a file, and after the file is written, it is closed automatically.

We wrote the file in the “dir” folder, as attached in the above screenshot, and we also attached a screenshot of the data.json file. For better readability and pretty printing, we passed an indent of 4.

Reading JSON from a file

You can use the built-in json.load() method to deserialize JSON from a file to a Python object.

Open the file in read mode (‘r’), load it, and read the content.

import json

with open('dir/data.json', 'r') as file:
    loaded_data = json.load(file)

print(loaded_data)

# Output:
# {'title': 'HP and Half blood Prince', 'author': 'JK Rowling', 'pages': 544, 'genres': 'fantasy', 'rating': 4.7}

Empty file

If the JSON file you are trying to read is empty, it throws json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0).

import json

with open('dir/data.json', 'r') as file:
    loaded_data = json.load(file)

print(loaded_data)

# json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

To fix this type of error or prevent it from occurring, always wrap in try-except for robustness.

import json

try:
    with open('dir/data.json', 'r') as file:
        json.load(file)
except json.JSONDecodeError:
    print("Empty or invalid JSON")

# Output: Empty or invalid JSON

That’s all!