Creating dictionary from two sequences in Python - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this dictionary creation?

Given two lists, what is the resulting dictionary after running this code?

Python

keys = ['a', 'b', 'c']
values = [1, 2, 3]
result = dict(zip(keys, values))
print(result)

A {'a': 1, 'b': 2, 'c': 3}

B {'a': 1, 'b': 2}

C {'a': 1, 'b': 2, 'c': 3, 'd': 4}

D TypeError

💡 Hint

Think about how zip pairs elements from two lists.

The zip function pairs elements from keys and values by position. Then dict() converts these pairs into key-value pairs in the dictionary.

❓ Predict Output

intermediate

What happens if the sequences have different lengths?

What is the output of this code when keys and values have different lengths?

Python

keys = ['x', 'y', 'z', 'w']
values = [10, 20]
result = dict(zip(keys, values))
print(result)

A {'x': 10, 'y': 20, 'z': 0, 'w': 0}

B {'x': 10, 'y': 20, 'z': None, 'w': None}

C IndexError

D {'x': 10, 'y': 20}

💡 Hint

zip stops when the shortest input is exhausted.

zip stops pairing when the shortest list ends, so only first two pairs are created.

❓ Predict Output

advanced

What is the output of this dictionary comprehension?

What does this code print?

Python

keys = ['a', 'b', 'c']
values = [1, 2, 3]
result = {k: v*2 for k, v in zip(keys, values)}
print(result)

A {'a': 1, 'b': 2, 'c': 3}

B TypeError

C {'a': 2, 'b': 4, 'c': 6}

D {'a': 2, 'b': 4}

💡 Hint

Look at how values are transformed inside the comprehension.

Each value is multiplied by 2 before being assigned to the key.

❓ Predict Output

advanced

What error does this code raise?

What error occurs when trying to create a dictionary from these sequences?

Python

keys = ['a', 'b', 'a']
values = [1, 2, 3]
result = dict(zip(keys, values))
print(result)

A KeyError

B {'a': 3, 'b': 2}

C ValueError

D TypeError

💡 Hint

What happens if keys repeat in a dictionary?

Duplicate keys overwrite previous values. The last value for 'a' is kept.

🧠 Conceptual

expert

How many items are in the dictionary created here?

Given these sequences, how many key-value pairs will the dictionary have?

Python

keys = ['k1', 'k2', 'k3', 'k4']
values = [10, 20, 30, 40, 50]
result = dict(zip(keys, values))
print(len(result))

A 4

B 5

C 3

D IndexError

💡 Hint

zip stops at the shortest sequence length.

zip pairs only four items because keys has length 4, so dictionary has 4 items.