Working with JSON files in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Reading JSON data from a file

What is the output of this Python code that reads a JSON file and prints the data?

Python

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

A {'name': 'Alice', 'age': 30}

B "{'name': 'Alice', 'age': 30}"

C SyntaxError

D FileNotFoundError

💡 Hint

Remember json.load reads JSON and converts it to Python objects.

json.load reads the JSON file and converts it to a Python dictionary. The print statement outputs the dictionary.

❓ Predict Output

intermediate

Writing Python dictionary to JSON file

What will be the content of 'output.json' after running this code?

Python

import json
data = {'city': 'Paris', 'population': 2148327}
with open('output.json', 'w') as f:
    json.dump(data, f)

A {"city": "Paris", "population": 2148327}

B {'city': 'Paris', 'population': 2148327}

C SyntaxError

D TypeError

💡 Hint

json.dump writes JSON formatted string to file with double quotes.

json.dump converts the dictionary to a JSON string with double quotes and writes it to the file.

❓ Predict Output

advanced

Handling JSON decoding errors

What error will this code raise when trying to load invalid JSON content?

Python

import json
invalid_json = '{"name": "Bob", age: 25}'
data = json.loads(invalid_json)

A TypeError

B No error, data is loaded

C KeyError

D json.decoder.JSONDecodeError

💡 Hint

JSON keys must be in double quotes.

The JSON string is invalid because the key 'age' is not in double quotes, causing JSONDecodeError.

❓ Predict Output

advanced

Using json.dumps with indentation

What is the output of this code?

Python

import json
data = {'fruit': 'apple', 'count': 5}
result = json.dumps(data, indent=2)
print(result)

A {"fruit": "apple", "count": 5}

B

{
  "fruit": "apple",
  "count": 5
}

C SyntaxError

D TypeError

💡 Hint

indent=2 adds line breaks and spaces for readability.

json.dumps with indent=2 formats the JSON string with new lines and two spaces indentation.

🧠 Conceptual

expert

Understanding JSON serialization of custom objects

What happens when you run this code?

Python

import json
class Person:
    def __init__(self, name):
        self.name = name
p = Person('Eve')
json.dumps(p)

A {"name": "Eve"}

B "{'name': 'Eve'}"

C TypeError: Object of type Person is not JSON serializable

D No output, code runs silently

💡 Hint

json.dumps can only serialize basic Python types by default.

Custom objects like Person are not serializable by default, causing TypeError.