Dictionary creation in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of dictionary comprehension with condition

What is the output of this Python code?

Python

result = {x: x**2 for x in range(5) if x % 2 == 0}
print(result)

A {0: 0, 2: 4, 4: 16}

B {1: 1, 3: 9}

C {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

D SyntaxError

💡 Hint

Look at the condition after the for loop in the comprehension.

The comprehension includes only even numbers (x % 2 == 0). So keys are 0, 2, 4 with their squares as values.

❓ Predict Output

intermediate

Output of dictionary from zip function

What does this code print?

Python

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

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

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

C TypeError

D {('a', 1), ('b', 2), ('c', 3)}

💡 Hint

zip pairs elements from two lists into tuples.

dict(zip(keys, values)) creates a dictionary pairing each key with its corresponding value.

❓ Predict Output

advanced

Output of nested dictionary comprehension

What is the output of this code?

Python

result = {x: {y: x*y for y in range(3)} for x in range(2)}
print(result)

A SyntaxError

B {0: {0: 0, 1: 1, 2: 2}, 1: {0: 0, 1: 1, 2: 2}}

C {0: {0: 0, 1: 0, 2: 0}, 1: {0: 1, 1: 1, 2: 1}}

D {0: {0: 0, 1: 0, 2: 0}, 1: {0: 0, 1: 1, 2: 2}}

💡 Hint

The inner dictionary multiplies x by y for y in 0 to 2.

For x=0, all products are 0. For x=1, products are 0,1,2. So nested dicts reflect these values.

❓ Predict Output

advanced

Output of dictionary creation with duplicate keys

What is the output of this code?

Python

result = {x % 3: x for x in range(6)}
print(result)

A {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5}

B {0: 0, 1: 1, 2: 2}

C {0: 3, 1: 4, 2: 5}

D KeyError

💡 Hint

Keys repeat because of modulo operation; later values overwrite earlier ones.

Keys are 0,1,2 repeated twice. The last value for each key is kept in the dictionary.

🧠 Conceptual

expert

Error raised by invalid dictionary creation syntax

What error does this code raise?

Python

result = {x: x*2 if x > 2 for x in range(5)}

A TypeError

B SyntaxError

C KeyError

D No error, outputs {3: 6, 4: 8}

💡 Hint

Check the placement of the if condition in the dictionary comprehension.

The syntax is invalid because the if condition is inside the value expression without else, causing SyntaxError.