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JSON Data Handling

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JSON (JavaScript Object Notation) is a lightweight data interchange format that's easy for humans to read and write and easy for machines to parse and generate. In Python, the json module provides an easy way to encode and decode data in JSON format.

Key Concepts

  1. JSON Basics:

    • JSON is built on two structures:
      • A collection of name/value pairs (often realized as an object, record, struct, dictionary, hash table, keyed list, or associative array).
      • An ordered list of values (often realized as an array, vector, list, or sequence).

  2. Python json Module:

    • The json module in Python can be used to parse JSON from strings or files and convert Python dictionaries to JSON strings.

JSON Data Handling in Python

Importing the json Module

import json

Parsing JSON

From a JSON String

json_string = '{"name": "John", "age": 30, "city": "New York"}'
data = json.loads(json_string)
print(data)

Explanation:

  • json.loads() takes a JSON string and converts it into a Python dictionary.

From a JSON File

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

Explanation:

  • json.load() reads JSON data from a file and converts it into a Python dictionary.

Writing JSON

To a JSON String

data = {
    "name": "John",
    "age": 30,
    "city": "New York"
}
json_string = json.dumps(data)
print(json_string)

Explanation:

  • json.dumps() takes a Python dictionary and converts it into a JSON string.

To a JSON File

data = {
    "name": "John",
    "age": 30,
    "city": "New York"
}
with open('data.json', 'w') as file:
    json.dump(data, file)

Explanation:

  • json.dump() writes a Python dictionary to a file in JSON format.

Practical Examples

Example 1: Reading JSON from a File and Accessing Data

import json

# Read JSON data from a file
with open('data.json', 'r') as file:
    data = json.load(file)

# Accessing data
print(f"Name: {data['name']}")
print(f"Age: {data['age']}")
print(f"City: {data['city']}")

Example 2: Writing Data to a JSON File

import json

# Data to be written
data = {
    "name": "Alice",
    "age": 25,
    "city": "Los Angeles"
}

# Write JSON data to a file
with open('data.json', 'w') as file:
    json.dump(data, file, indent=4)  # indent=4 for pretty printing

Practical Exercises

Exercise 1: Parsing JSON from a String

Task: Given a JSON string, parse it and print each key-value pair.

json_string = '{"title": "Python Programming", "author": "John Doe", "year": 2021}'

# Your code here

Solution:

import json

json_string = '{"title": "Python Programming", "author": "John Doe", "year": 2021}'
data = json.loads(json_string)

for key, value in data.items():
    print(f"{key}: {value}")

Exercise 2: Writing a Dictionary to a JSON File

Task: Write the following dictionary to a JSON file named book.json.

book = {
    "title": "Learning Python",
    "author": "Mark Lutz",
    "year": 2013
}

Solution:

import json

book = {
    "title": "Learning Python",
    "author": "Mark Lutz",
    "year": 2013
}

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

Common Mistakes and Tips

  1. Incorrect JSON Format:

    • Ensure that the JSON string is correctly formatted. Common mistakes include missing quotes, commas, or braces.
    • Use online JSON validators to check the correctness of your JSON data.

  2. File Handling:

    • Always use with open() to handle files. This ensures that the file is properly closed after its suite finishes, even if an exception is raised.

  3. Pretty Printing:

    • Use the indent parameter in json.dump() and json.dumps() to make the JSON output more readable.

Conclusion

In this section, you learned how to handle JSON data in Python using the json module. You now know how to parse JSON from strings and files, and how to write JSON data to strings and files. These skills are essential for working with APIs and data interchange in Python. Next, you will learn about file and directory operations in Python.

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Python Programming Course

Module 1: Introduction to Python

Module 2: Control Structures

Module 3: Functions and Modules

Module 4: Data Structures

Module 5: Object-Oriented Programming

Module 6: File Handling

Module 7: Error Handling and Exceptions

Module 8: Advanced Topics

Module 9: Testing and Debugging

Module 10: Web Development with Python

Module 11: Data Science with Python

Module 12: Final Project

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