Writing and Reading JSON Files in Python

JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write, and easy for machines to parse and generate. Python is a high-level, interpreted programming language known for its simplicity, readability, and powerful libraries. In this article, we will dive into the world of JSON file handling in Python, learn how to create and read JSON files, and use Python’s built-in JSON library to our advantage.

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. JSON is based on two primary structures:

1. A collection of name/value pairs, also known as a “dictionary” or “object” in Python
2. An ordered list of values, also known as an “array” in Python

JSON data is represented as a string in text format, making it easier to transmit over networks and share between different programming languages. Let’s take a look at an example of JSON data.

{
  "name": "John",
  "age": 30,
  "city": "New York"
}

In this example, we have a dictionary with three name/value pairs: “name” with the value “John”, “age” with the value 30, and “city” with the value “New York”. The name/value pairs are separated by commas, and the entire dictionary is enclosed in curly braces.

Writing JSON Files in Python

To write JSON data in Python, we need to first import the built-in JSON library:

import json

Next, we will create a dictionary with some data to be written to a JSON file:

data = {
    'name': 'John',
    'age': 30,
    'city': 'New York'
}

We can use the `open()` function to create a new file, with the `w` argument indicating that we want to write to the file:

with open('data.json', 'w') as f:
    json.dump(data, f)

The `json.dump()` function takes in two parameters: the data to be written (in this case, the `data` dictionary) and the file object to write to (`f` in this example). This will create a new file called `data.json` in the current directory with the following contents:

{
    "name": "John",
    "age": 30,
    "city": "New York"
}

Reading JSON Files in Python

To read JSON data in Python, we can use the `json.load()` function to load the data from a file:

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

The `json.load()` function takes in a file object (`f` in this example) and returns the JSON data as a Python dictionary. We can then use the dictionary values in our Python code as needed.

Conclusion

In this article, we learned what JSON is and how it is used in Python as a data interchange format. We explored how to write JSON data to a file using Python’s built-in JSON library, and how to read JSON data from a file using the `json.load()` function. JSON is an important tool for transmitting and sharing data between different programming languages, and Python’s built-in JSON library makes it easy to work with JSON data in Python.