How to Convert a Python Dictionary to JSON

Key Takeaways

1. Use json.dumps() to convert a Python dictionary into a JSON-formatted string.
2. Use json.dump() to write JSON data directly to a file.
3. The indent parameter improves JSON readability with pretty-printing.

When working with Python, especially in web development or data exchange, converting a dictionary to JSON (JavaScript Object Notation) is a common and essential task. JSON is a lightweight data-interchange format that is easy for humans to read and write, and easy for machines to parse and generate.

In this article, we will explore how to convert a Python dictionary into a JSON string using the built-in json module, along with practical examples and tips.

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Importing the json Module

Python provides a standard library called json that enables you to encode and decode JSON data easily. Before you can use it, you need to import it:

import json

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Creating a Python Dictionary

Let’s start with a sample dictionary:

data = {
    "name": "Alice",
    "age": 30,
    "is_employee": True,
    "departments": ["HR", "Finance"],
    "details": {
        "position": "Manager",
        "full_time": True
    }
}

---

Converting Dictionary to JSON String

You can use the json.dumps() method to convert a Python dictionary to a JSON-formatted string.

json_string = json.dumps(data)
print(json_string)

Output:

{"name": "Alice", "age": 30, "is_employee": true, "departments": ["HR", "Finance"], "details": {"position": "Manager", "full_time": true}}

Note that:

• Python’s True and False become true and false in JSON.
• The dictionary is converted to a single-line JSON string by default.

---

Pretty-Printing JSON

To make the output more readable, you can use the indent parameter:

json_string = json.dumps(data, indent=4)
print(json_string)

Output:

{
    "name": "Alice",
    "age": 30,
    "is_employee": true,
    "departments": [
        "HR",
        "Finance"
    ],
    "details": {
        "position": "Manager",
        "full_time": true
    }
}

---

Writing JSON to a File

If you want to save the JSON data to a file, use json.dump() instead of dumps():

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

---

Conclusion

Converting a Python dictionary to JSON is straightforward with the json module. You can serialize your data for APIs, configuration files, or data storage with just a few lines of code. Remember to use dumps() for strings and dump() for writing directly to files, and leverage parameters like indent to improve readability.

FAQs

What’s the difference between json.dumps() and json.dump()?

dumps() returns a string; dump() writes directly to a file.

How do Boolean values convert from Python to JSON?

Python True and False become true and false in JSON.

Can I format the JSON output for better readability?

Yes, use the indent parameter in dumps() or dump().

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