Nested dictionaries in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a nested dictionary with a key 'person' and a nested key 'name'.

Python

data = {'person': {'name': [1]

Drag options to blanks, or click blank then click option'

Aname

BAlice

C'Alice'

D"name"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around string values.

Using variable names without defining them.

The value for the nested key 'name' must be a string, so it needs quotes. 'Alice' is correct.

2fill in blank

medium

Complete the code to access the nested value 'city' inside the 'address' dictionary.

Python

city = info['address'][[1]]

Drag options to blanks, or click blank then click option'

Acity

B'city'

C"address"

D'address'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the key without quotes.

Using the wrong key name.

To access a nested dictionary value, use the key as a string inside quotes. 'city' is the correct key.

3fill in blank

hard

Fix the error in the code to correctly add a nested dictionary under the key 'contact'.

Python

data['contact'] = [1]

Drag options to blanks, or click blank then click option'

A{'phone': '123-4567'}

B{phone: '123-4567'}

C['phone', '123-4567']

D('phone', '123-4567')

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys causing syntax errors.

Using list or tuple instead of dictionary.

Dictionary keys must be strings in quotes. Option A correctly creates a nested dictionary.

4fill in blank

hard

Fill both blanks to create a nested dictionary with keys 'student' and 'grade'.

Python

record = { [1]: [2] }

Drag options to blanks, or click blank then click option'

A'student'

B'grade'

C90

D{'grade': 90}

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the key 'student'.

Using a number instead of a dictionary for the value.

The outer key is 'student' (a string), and the value is a nested dictionary {'grade': 90}.

5fill in blank

hard

Fill both blanks to create a nested dictionary with keys 'team', 'player', and 'score'.

Python

game = { [1]: [2] }

Drag options to blanks, or click blank then click option'

A'team'

B{'player': 'John', 'score': 10}

C'player'

D'score'

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting keys.

Using incorrect data types for nested values.

The outer key is 'team'. The value is a dictionary with keys 'player' and 'score'. Here, we fill the outer key and the nested dictionary.

Practice

1. What is a nested dictionary in Python?
Example: {'person': {'name': 'Alice', 'age': 30}}

easy

A. A dictionary with only one key

B. A dictionary inside another dictionary

C. A list inside a dictionary

D. A dictionary with numeric keys only

Solution

1. Step 1: Understand dictionary structure

   A dictionary stores key-value pairs. Nested means one value is itself a dictionary.

2. Step 2: Analyze the example

   In {'person': {'name': 'Alice', 'age': 30}}, the value for 'person' is another dictionary.

3. Final Answer:

   A dictionary inside another dictionary -> Option B

4. Quick Check:

   Nested dictionary = dictionary inside dictionary [OK]

Hint: Look for a dictionary as a value inside another dictionary [OK]

Common Mistakes:

• Confusing nested dictionary with list inside dictionary
• Thinking nested means only one key
• Assuming keys must be numbers

2. Which of the following is the correct way to access the value 'blue' in this nested dictionary?

colors = {'shirt': {'color': 'blue', 'size': 'M'}}

easy

A. colors['shirt']['size']

B. colors['color']['shirt']

C. colors['shirt']['color']

D. colors['color']

Solution

1. Step 1: Identify keys to reach 'blue'

   'blue' is the value of 'color' inside the dictionary for key 'shirt'.

2. Step 2: Use correct key order

   Access outer key 'shirt' first, then inner key 'color': colors['shirt']['color'].

3. Final Answer:

   colors['shirt']['color'] -> Option C

4. Quick Check:

   Outer then inner keys = colors['shirt']['color'] [OK]

Hint: Use outer key first, then inner key in square brackets [OK]

Common Mistakes:

• Swapping the order of keys
• Trying to access keys that don't exist
• Using only one key for nested value

3. What will be the output of this code?

data = {'user': {'name': 'Bob', 'age': 25}}
print(data['user']['age'])

medium

A. 25

B. Bob

C. {'name': 'Bob', 'age': 25}

D. KeyError

Solution

1. Step 1: Access nested dictionary value

   data['user'] gives {'name': 'Bob', 'age': 25}.

2. Step 2: Access 'age' key inside nested dictionary

   data['user']['age'] gives 25.

3. Final Answer:

   25 -> Option A

4. Quick Check:

   Nested key access returns 25 [OK]

Hint: Access keys step-by-step to get nested value [OK]

Common Mistakes:

• Printing the whole nested dictionary instead of value
• Using wrong key order
• Expecting string 'Bob' instead of age

4. Find the error in this code snippet:

info = {'book': {'title': 'Python 101', 'pages': 200}}
print(info['book']['author'])

medium

A. No error, prints None

B. SyntaxError due to missing colon

C. TypeError because 'book' is not a dictionary

D. KeyError because 'author' key does not exist

Solution

1. Step 1: Check keys in nested dictionary

   info['book'] has keys 'title' and 'pages', but no 'author'.

2. Step 2: Accessing missing key causes error

   Trying info['book']['author'] raises KeyError because 'author' is missing.

3. Final Answer:

   KeyError because 'author' key does not exist -> Option D

4. Quick Check:

   Missing key access = KeyError [OK]

Hint: Check if key exists before accessing nested dictionary [OK]

Common Mistakes:

• Assuming missing keys return None
• Confusing KeyError with SyntaxError
• Thinking nested dictionary keys are always present

5. Given this nested dictionary:

students = {
  'Alice': {'math': 90, 'science': 85},
  'Bob': {'math': 75, 'science': 95}
}

Which code correctly adds a new subject 'english' with score 88 for Alice?

hard

A. students['Alice']['english'] = 88

B. students['english']['Alice'] = 88

C. students['Alice'] = {'english': 88}

D. students['english'] = {'Alice': 88}

Solution

1. Step 1: Identify where to add new subject

   We want to add 'english' score inside Alice's dictionary.

2. Step 2: Add key-value pair inside nested dictionary

   Use students['Alice']['english'] = 88 to add the new subject and score.

3. Final Answer:

   students['Alice']['english'] = 88 -> Option A

4. Quick Check:

   Add key inside nested dict = students['Alice']['english'] = 88 [OK]

Hint: Add new key inside inner dictionary using outer then inner keys [OK]

Common Mistakes:

• Replacing entire inner dictionary instead of adding key
• Adding key at wrong dictionary level
• Swapping keys order