How to Read and Parse JSON Data in Python?

JSON (Javascript Object Notation) is currently the most popular data transmission format. Almost 50% of the sites worldwide use this format. 

It is lightweight and formatted in such a way that is easily readable for humans and machines. JSON is also compatible with a lot of programming languages—including Python. 

This article will cover how to read and parse JSON files in Python with easy-to-understand examples. Keep reading to learn more.

🔑 Key Takeaways

• JSON is a widely used format, compatible with various programming languages, even Python.
• The json module in Python allows easy conversion between JSON data and Python dictionaries using loads() and load()functions for JSON string and file parsing.
• Python dictionaries can be converted to JSON objects with the dumps() and dump() functions from the json module.

• The load() function is particularly useful for reading larger JSON files, directly converting them into Python dictionaries.
• Understanding the json module’s capabilities in Python is essential for seamless data interchange between JSON and Python dictionaries.

Methods to Read and Parse JSON Data in Python

Parsing entails different tools and languages, depending on the format of data that needs to be parsed.  Luckily, JSON is a format that is compatible with most tools and programming languages. 

When reading or parsing JSON files using Python, the language supports JSON through the pre-installed module known as “json.” 

Python calls forth this module like this:

import json

The json module is capable of converting JSON strings or files into Python dictionaries and vice versa. Here is a table of JSON objects and their corresponding Python data types:

For JSON to be readable in Python, its objects must be converted to the corresponding Python data type.

Reading JSON for Python Dictionary Conversion

Reading a JSON file in Python always leads to an actual conversion from JSON objects to Python dictionaries. This is done by the functions load and loads (read as load-s or load string) in the json module.

JSON String to Python Dict

Here is an example of a JSON string:

{
  "name": "John Doe",
  "age": 30,
  "address": {
    "street": "123 Main Street",
    "city": "New York",
    "state": "NY"
  },
  "isPreferredCustomer": true,
  "notes": null
}

To convert this into a Python dict, use the loads() function. Here’s the script:

import json

# Example JSON string
json_string = """
{
  "name": "John Doe",
  "age": 30,
  "address": {
    "street": "123 Main Street",
    "city": "New York",
    "state": "NY"
  },
  "isPreferredCustomer": true,
  "notes": null
} """

python_dict = json.loads(json_string)
print(python_dict)
print(type(python_dict))

# Output

json_dict = {'name': 'John Doe', 'age': 30, 'address': {'street': '123 Main Street', 'city': 'New York', 'state': 'NY'}, 'isPreferredCustomer': True, 'notes': None}
<class 'dict'>

The JSON object is successfully converted to a Python dictionary. This is confirmed by the type() function, which printed the <class ‘dict’> result.

Reading JSON Files 

The same process is required when parsing a JSON file. To do that, you can employ the load() function. 

Say you have a JSON file named exampleuser.json that has the same content as the sample JSON string above.

To read this JSON file, you can: 

1. Use the open() function in reading (‘r’) mode. 
2. The load() function converts it into a Python dict. 
3. The type() function confirms the data type.

import json

with open('exampleuser.json', 'r') as json_file:
    python_dict = json.load(json_file)
    print(python_dict)
    print(type(python_dict))

# Output python_dict = {'name': 'John Doe', 'age': 30, 'address': {'street': '123 Main Street', 'city': 'New York', 'state': 'NY'}, 'isPreferredCustomer': True, 'notes': None}
<class 'dict'>

Converting Python Dictionaries into JSON

Recall the capability of Python’s json module to convert dictionaries into JSON objects discussed earlier.

In this case, you will make use of the functions dump and dumps (read as dump-s or dump string).

Python Dict to JSON String

Use the dumps() function to convert Python dictionaries into JSON strings. Here is an example:

import json

python_dict = "{'name': 'John Doe', 'age': 30, 'address': {'street': '123 Main Street', 'city': 'New York', 'state': 'NY'}, 'isPreferredCustomer': True}"

json_string = json.dumps(python_dict)

print(json_string)
print(type(json_string))

# Output
json_string = "{'name': 'John Doe', 'age': 30, 'address': {'street': '123 Main Street', 'city': 'New York', 'state': 'NY'}, 'isPreferredCustomer': True}"
<class 'str'>

Conversion without data loss is a key advantage of JSON. To make it more readable, you can add the indent argument within the dumps() function.

json_string = json.dumps (python_dict, indent=4)

This should return a more readable output, like: 

{
  "name": "John Doe",
  "age": 30,
  "address": {
    "street": "123 Main Street",
    "city": "New York",
    "state": "NY"
  },
  "isPreferredCustomer": True,
}

Writing Python String into a JSON File

You have to use the dump() function to achieve this. Again, the open() function will open an existing file as indicated. 

If it does not exist, it will be automatically created with the help of the write (‘w’) mode. The write mode will also change the content of the file in case it does exist.

Here is a sample script:

import json

python_dict = "{'name': 'John Doe', 'age': 30, 'address': {'street': '123 Main Street', 'city': 'New York', 'state': 'NY'}, 'isPreferredCustomer': True}"

with open('exampleuser.json', 'w') as json_file:
    json.dump(python_dict, json_file)
    print(type(json_file))

Once done, you now know how to read and parse JSON using a Python module.

Conclusion

The JSON module is vital in providing a straightforward way of reading and parsing JSON—with just a few lines of code. 

However, this is nowhere near its full capabilities. Make sure to review the json module’s official documentation to dig for more.

FAQs

By Muninder Adavelli

Muninder Adavelli is a core team member and Digital Growth Strategist at Techjury. With a strong background in marketing and a deep understanding of technology's role in digital marketing, he brings immense value to the TechJury team.