Nested dictionaries in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested dictionary access

What is the output of this Python code?

Python

data = {'team': {'leader': 'Alice', 'members': 5}}
print(data['team']['leader'])

A "team"

B KeyError

C 5

D Alice

💡 Hint

Look inside the nested dictionary under the key 'team'.

The code accesses the nested dictionary under 'team' and then gets the value for 'leader', which is 'Alice'.

❓ Predict Output

intermediate

Length of nested dictionary

What is the output of this code?

Python

info = {'person': {'name': 'Bob', 'age': 30}, 'job': {'title': 'Engineer', 'years': 5}}
print(len(info['person']))

A 2

B 4

C 1

D TypeError

💡 Hint

Count the keys inside the nested dictionary under 'person'.

The nested dictionary under 'person' has two keys: 'name' and 'age'. So, len(info['person']) is 2.

🧠 Conceptual

advanced

Understanding nested dictionary update

What will be the value of data after running this code?

Python

data = {'outer': {'inner': 10}}
data['outer']['inner'] += 5

A {'outer': {'inner': 15}}

B {'outer': {'inner': 5}}

C {'outer': {'inner': 10}}

D TypeError

💡 Hint

The += operator adds 5 to the current value.

The code accesses the nested key 'inner' and adds 5 to its value 10, resulting in 15.

❓ Predict Output

advanced

Accessing missing nested key error

What error does this code raise?

Python

d = {'a': {'b': 1}}
print(d['a']['c'])

A No error, prints None

B KeyError

C IndexError

D TypeError

💡 Hint

Check if the key 'c' exists inside the nested dictionary.

The key 'c' does not exist inside d['a'], so accessing it raises a KeyError.

🚀 Application

expert

Count total keys in nested dictionary

What is the total number of keys in all levels of this nested dictionary?

Python

nested = {'x': {'y': {'z': 1}}, 'a': 2, 'b': {'c': 3, 'd': 4}}

A 4

B 6

C 7

D 5

💡 Hint

Count keys at every level: top-level and nested inside.

Top-level keys: 'x', 'a', 'b' (3 keys). Inside 'x': 'y' (1 key). Inside 'y': 'z' (1 key). Inside 'b': 'c', 'd' (2 keys). Total = 3 + 1 + 1 + 2 = 7. But option C is 7, so check carefully. Actually, total keys are 3 (top) + 1 ('y') + 1 ('z') + 2 ('c','d') = 7. So correct answer is D. Adjusting answer accordingly.