How to Read JSON in Python

Key Takeaways

1. Use json.loads() to parse JSON strings into Python objects.
2. Use json.load() to read JSON data from a file.
3. Always handle exceptions like JSONDecodeError and FileNotFoundError.

JSON (JavaScript Object Notation) is a popular data format used for storing and exchanging data. Python provides built-in support for JSON through the json module, making it easy to work with JSON data in your programs. In this article, we’ll explore how to read JSON from strings and files using Python.

What is JSON?

JSON is a lightweight data-interchange format that is easy for humans to read and write, and easy for machines to parse and generate. It’s commonly used in web APIs and configuration files.

A typical JSON object looks like this:

{
  "name": "Alice",
  "age": 30,
  "is_student": false,
  "courses": ["Math", "Science"]
}

Reading JSON Strings

Python’s json.loads() method can parse a JSON-formatted string and convert it into a Python dictionary:

import json

json_string = '{"name": "Alice", "age": 30, "is_student": false, "courses": ["Math", "Science"]}'

data = json.loads(json_string)

print(data["name"])  # Output: Alice

Reading JSON from a File

To read a JSON file, use the json.load() method. This method reads from a file object and parses the JSON data:

import json

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

print(data["courses"])  # Output: ['Math', 'Science']

Notes:

• Use the with statement to open files, as it ensures that the file is properly closed after reading.
• json.load() should not be confused with json.loads(). The former reads from a file object, while the latter reads from a string.

Handling Errors

When working with JSON, you should always anticipate possible parsing errors:

import json

try:
    with open("data.json", "r") as file:
        data = json.load(file)
except json.JSONDecodeError as e:
    print("Failed to decode JSON:", e)
except FileNotFoundError:
    print("The file was not found.")

Conclusion

Reading JSON in Python is straightforward thanks to the json module. Whether you’re working with a string or a file, Python makes it easy to parse and work with JSON data structures. This is particularly useful when dealing with APIs, configuration files, or data exchange between systems.

FAQs

What is the difference between json.load() and json.loads()?

json.load() reads from a file object; json.loads() parses a JSON string.

How do I avoid errors when reading JSON files?

Use try-except blocks to handle decoding and file-not-found errors.

Can Python handle nested JSON structures?

Yes, nested JSON is parsed into nested Python dictionaries and lists.

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