Serializing and deserializing JSON in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this JSON serialization code?

Consider this Python code that serializes a dictionary to a JSON string. What will be printed?

Python

import json

data = {'name': 'Alice', 'age': 30, 'is_student': False}
json_str = json.dumps(data)
print(json_str)

A {"name": "Alice", "age": 30, "is_student": True}

B {'name': 'Alice', 'age': 30, 'is_student': False}

C {"name": "Alice", "age": "30", "is_student": false}

D {"name": "Alice", "age": 30, "is_student": false}

💡 Hint

Remember that JSON uses double quotes and lowercase true/false for booleans.

The json.dumps function converts Python objects to JSON strings. It uses double quotes for keys and string values, and converts Python False to JSON false.

❓ Predict Output

intermediate

What is the value of 'data' after deserializing this JSON string?

Given this JSON string, what Python object results from deserializing it?

Python

import json

json_str = '{"fruits": ["apple", "banana"], "count": 2}'
data = json.loads(json_str)
print(data)

A {'fruits': ['apple', 'banana'], 'count': 2}

B {"fruits": ["apple", "banana"], "count": 2}

C {fruits: ['apple', 'banana'], count: 2}

D ['apple', 'banana', 2]

💡 Hint

json.loads converts JSON strings to Python dictionaries and lists.

The JSON string represents an object with a list and a number. json.loads converts it to a Python dict with a list and int.

❓ Predict Output

advanced

What error does this code raise when serializing?

What error will this code raise when trying to serialize the object to JSON?

Python

import json

class Person:
    def __init__(self, name):
        self.name = name

p = Person('Bob')
json_str = json.dumps(p)

A TypeError: Object of type Person is not JSON serializable

B ValueError: Invalid JSON format

C AttributeError: 'Person' object has no attribute 'name'

D No error, outputs '{}'

💡 Hint

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

Custom objects like Person are not serializable by default and cause a TypeError.

❓ Predict Output

advanced

What is the output of this code using json.loads with an invalid JSON string?

What happens when you run this code?

Python

import json

invalid_json = '{"name": "Alice", age: 30}'
data = json.loads(invalid_json)

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

B json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes

C SyntaxError: invalid syntax

D TypeError: string indices must be integers

💡 Hint

JSON keys must be double quoted strings.

The key 'age' is not enclosed in double quotes, so json.loads raises JSONDecodeError.

🧠 Conceptual

expert

Which option correctly serializes a Python dictionary with non-string keys to JSON?

Given a Python dictionary with integer keys, which option produces a valid JSON string with string keys?

Python

import json

data = {1: 'one', 2: 'two'}

A json.dumps(dict(map(str, data.items())))

B json.dumps(data)

C json.dumps({str(k): v for k, v in data.items()})

D json.dumps(data, ensure_ascii=False)

💡 Hint

JSON keys must be strings. Python dict keys can be other types.

Option C converts integer keys to strings before serializing, producing valid JSON. Option C raises TypeError. Option C is invalid syntax. Option C does not fix non-string keys.