How to Write JSON to a File in Python

Key Takeaways

1. Use Python's built-in json module for JSON file operations.
2. json.dump() writes Python dictionaries to a file as JSON.
3. Adding indent improves readability of the output.

JSON (JavaScript Object Notation) is a lightweight data format widely used for data exchange between systems. In Python, working with JSON is simple thanks to the built-in json module. This article will guide you through the steps to write JSON data to a file using Python.

Why Use JSON in Python?

JSON is both human-readable and easy to parse, making it ideal for storing configuration, transmitting data between a server and a client, or even saving application data locally. Python's json module provides convenient methods to handle JSON serialization and deserialization.

Step 1: Import the JSON Module

To work with JSON in Python, you first need to import the json module:

import json

Step 2: Create a Python Dictionary

Before writing to a JSON file, you typically have your data in the form of a Python dictionary or list:

data = {
    "name": "Alice",
    "age": 30,
    "email": "alice@example.com",
    "skills": ["Python", "Data Analysis", "Machine Learning"]
}

Step 3: Write JSON to a File

To write JSON data to a file, use the json.dump() method:

with open("data.json", "w") as file:
    json.dump(data, file)

This will create a file named data.json and write the dictionary into it in JSON format.

Optional: Pretty Printing the JSON Output

For better readability, you can format the JSON with indentation:

with open("data_pretty.json", "w") as file:
    json.dump(data, file, indent=4)

This adds whitespace and line breaks, making the file easier to read.

Step 4: Confirm the File Contents (Optional)

You can verify that the JSON data was written correctly by opening the file manually or reading it back in Python:

with open("data.json", "r") as file:
    loaded_data = json.load(file)
    print(loaded_data)

Conclusion

Writing JSON data to a file in Python is straightforward using the json.dump() method. Whether you're saving user settings, application logs, or exporting data, JSON is a flexible and widely supported format. Remember to format your output with indent if you want a human-readable result.

FAQs

What data types can be written to a JSON file in Python?

You can write Python dictionaries, lists, strings, numbers, and booleans.

How do I make the JSON file more readable?

Use the indent parameter in json.dump() to format the output.

Is json.dump() the same as json.dumps()?

No, json.dump() writes to a file, while json.dumps() returns a JSON string.

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