Python read json to dictionary

Convert JSON to Dictionary in Python

This blog discusses how to convert JSON data to a dictionary in Python using the json.loads() method. It covers the basics of JSON and dictionaries, and provides sample code and tips for working with JSON data in Python, including how to handle nested JSON objects, JSON arrays, and invalid JSON strings.

Introduction

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. In Python, a JSON string can be easily converted into a dictionary object. In this article, we will explain how to convert JSON to a dictionary in Python and provide a sample program.

Understanding JSON

JSON is a format for representing data that consists of attribute-value pairs. The attribute is a string, and the value can be a string, number, boolean, null, or another JSON object or array. Here is an example of a JSON object:

In this example, the object has three attributes: name , age , and city . The values of these attributes are respectively «John», 30, and «New York».

Converting JSON to Dictionary in Python

Python has a built-in module called json that provides methods for parsing and generating JSON data. To convert a JSON string to a dictionary object in Python, we need to use the json.loads() method.

The json.loads() method takes a JSON string as input and returns a dictionary object. Here is the basic syntax for using this method:

import json json_string = '' dictionary = json.loads(json_string) print(dictionary) 

In this example, we first import the json module. We then define a JSON string that we want to convert to a dictionary. We pass this string to the json.loads() method, which returns a dictionary object. Finally, we print the dictionary object to the console.

The output of this program should be:

Handling Nested JSON Objects

JSON objects can be nested, which means that a value in a JSON object can be another JSON object. Here is an example of a nested JSON object:

In this example, the address attribute contains another JSON object with four attributes: street , city , state , and zip .

To convert a nested JSON object to a dictionary in Python, we can use the same json.loads() method. The only difference is that the value of a nested attribute in the JSON string will be another JSON string. We can convert this nested JSON string to a dictionary using the same json.loads() method.

Here is an example program that converts a nested JSON object to a dictionary in Python:

import json json_string = ''' < "name": "John", "age": 30, "address": < "street": "123 Main St", "city": "New York", "state": "NY", "zip": "10001" >> ''' dictionary = json.loads(json_string) print(dictionary) 

The output of this program should be:

Handling JSON Arrays

JSON arrays are collections of values that are enclosed in square brackets. Here is an example of a JSON array:

In this example, the array contains three JSON objects, each with three attributes: name , age , and city .

To convert a JSON array to a list of dictionaries in Python, we can use the same json.loads() method. The only difference is that the JSON string will start and end with square brackets, indicating that it is an array. We can iterate through the array and convert each JSON object to a dictionary using the json.loads() method.

Here is an example program that converts a JSON array to a list of dictionaries in Python:

import json json_string = ''' [ < "name": "John", "age": 30, "city": "New York" >, < "name": "Mary", "age": 25, "city": "Los Angeles" >, < "name": "Bob", "age": 40, "city": "Chicago" >] ''' list_of_dictionaries = json.loads(json_string) for dictionary in list_of_dictionaries: print(dictionary) 

The output of this program should be:

Handling Invalid JSON

If the input JSON string is invalid, the json.loads() method will raise a json.JSONDecodeError exception. This can happen if the JSON string is not properly formatted, or if it contains values that are not supported by JSON.

Here is an example program that tries to convert an invalid JSON string to a dictionary in Python:

import json json_string = '' dictionary = json.loads(json_string) print(dictionary) 

The output of this program should be:

json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1) 

This error occurs because the attribute names in the JSON string are not enclosed in double quotes, which is a requirement in JSON.

To handle invalid JSON, we can use a try-except block to catch the json.JSONDecodeError exception. We can then print an error message to the console and handle the exception appropriately.

Here is an example program that handles an invalid JSON string in Python:

import json json_string = '' try: dictionary = json.loads(json_string) except json.JSONDecodeError as e: print("Invalid JSON string:", e) 

The output of this program should be:

Invalid JSON string: Expecting property name enclosed in double quotes: line 1 column 2 (char 1) 

Conclusion

In conclusion, converting JSON to a dictionary in Python is a simple and useful operation that can help you work with JSON data in your Python applications. By using the json.loads() method, you can easily convert JSON strings to dictionaries and manipulate the data using standard dictionary operations. Additionally, understanding how to handle nested JSON objects, JSON arrays, and invalid JSON strings will help you work with JSON data in a variety of real-world scenarios.

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Convert JSON to a Python Dictionary

In this tutorial, you’re going to learn how to convert a JSON file or string into a Python dictionary. Being able to work with JSON data is an important skill for a Python developer of any skill level. In most cases, data you access through web APIs will come in the form JSON data. Being able to convert these JSON objects into Python dictionaries will allow you to work with the data in meaningful ways.

By the of this tutorial, you’ll have learned:

• How to load a JSON file into a Python dictionary
• How to load a JSON string into a dictionary
• How to load data from an API into a Python dictionary

What is JSON?

JSON stands for JavaScript Object Notation and it’s a popular format used to represent data. While originating from JavaScript, the format spread quickly due to its versatility. The format itself is quite similar to that of a Python dictionary. However, in many cases, the data comes in a string representing the object. We need to convert that string into a Python dictionary in order to work with it in Python.

Using JSON with Python

Python comes with a built-in library, json , that lets you work with JSON objects in meaningful ways. In this tutorial, we’ll be looking at two of its functions that allow you to convert JSON objects to Python dictionaries:

• json.load() , which loads a JSON file into a Python dictionary
• json.loads() , which loads a string representation of a JSON file into a Python dictionary

In the second function, as you may have guessed, the s suffix refers to string . In the following sections, you’ll learn how to use these functions to convert a JSON object into a Python dictionary.

Load a JSON File into a Python dictionary

In this section, you’ll learn how to use the json.load() function to load a JSON file into a Python dictionary. If you want to follow along, you can download the file here. The file represents data from the internal space station, the API we’ll explore later on in the tutorial.

Let’s see how you can use the load() function to load an external JSON file:

# Loading a JSON File to a Python Dictionary import json with open('/Users/nikpi/Desktop/iss-now.json', 'r') as file: data = json.load(file) print(data) # Returns: # , 'timestamp': 1652700632>

Let’s break down what we did in the code above:

1. We loaded the json library
2. We used a context manager to load our file in “read” mode using the alias file
3. We then used the json.load() function to load our file into a variable, data
4. Finally, we printed our resulting dictionary

While you can do this without using a context manager, the context manager handles closing the file, thereby preserving memory.

We can verify the type of the resulting value by using the type() function. This allows us to make sure that we actually loaded in a dictionary:

# Checking the Type of Our Loaded Dictionary import json with open('/Users/nikpi/Desktop/iss-now.json', 'r') as file: data = json.load(file) print(type(data)) # Returns: #

In some cases, however, you won’t be working with data in a .json file. In some cases, you’ll simply be presented with a string that represents the JSON object. In the following section, you’ll learn how to work with strings that represent JSON objects.

Load a JSON String into a Python Dictionary

In many cases, you’ll be given JSON data in a string format. Working with this is different than working with a .json file. When working with string representations of a JSON file, you can use the json.loads() function, which is used to “load a string”.

Let’s see how we can do this in Python using the json module:

# Loading a JSON String into a Python Dictionary import json json_data = ''' < "message": "success", "iss_position": < "latitude": "41.8157", "longitude": "-138.3051" >, "timestamp": 1652700632 > ''' data = json.loads(json_data) print(data) # Returns: # , 'timestamp': 1652700632>

We can see from the example above that by passing in the string into the json.loads() function, that we were able to easily transform a JSON string into a Pyhon dictionary. In the final section below, you’ll learn how to use the json.loads() function to load a JSON response object from a web API into a Python dictionary.

Load JSON Data from an API into a Python Dictionary

In this section, you’ll learn how to use the json and requests libraries to get data from a web API and load it into a Python dictionary. For this, we’ll be using a NASA API that describes the current status of the International Space Station, which you can find here. The endpoint we’ll use the iss-now endpoint, which provides the current location.

Let’s see how we can use the json library to load the response we get back:

# Loading JSON Data from a Web API into a Python Dictionary import json import requests url = 'http://api.open-notify.org/iss-now.json' response = requests.get(url) text = response.text print(json.loads(text)) # Returns: # , 'timestamp': 1652719740>

Let’s break down what we did here:

1. We imported the required libraries, json and requests
2. We loaded the response variable using the requests.get() function, passing in our url
3. We then got the text representation from the response object
4. Finally, we passed this into the json.loads() function to convert the string into a dictionary

This is quite a bit of code and thankfully there’s an easier way! The requests library allows us to apply the .json() method to the response object to convert it to a dictionary.

Let’s take a look at how this works:

# Convert an API JSON Response to a Python Dictionary import requests url = 'http://api.open-notify.org/iss-now.json' response = requests.get(url) data = response.json() print(data) # Returns: # , 'timestamp': 1652720039>

In the example above, we didn’t need to import the json library to convert the string into a Python dictionary. This works by loading a response object using the .get() function. We then apply the .json() method to the response object to convert it to a Python dictionary.

Conclusion

In this tutorial, you learned how to convert JSON into a Python dictionary. You learned three different ways of accomplishing this: first by loading a .json file into a Python dictionary, then by loading a JSON string into a dictionary, and, finally, working with web APIs.

Being able to work with JSON data is an important skill, given the ubiquity of the file format. Being able to convert this format to a Python dictionary will help you work with both web development and data science.

Additional Resources

To learn more about related topics, check out the tutorials below:

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