Basic dictionary comprehension 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, 1: 1, 2: 4, 3: 9, 4: 16}

B {1: 1, 3: 9}

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

D SyntaxError

💡 Hint

Look at the condition after the for loop inside 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

Dictionary comprehension with ternary expression

What does this code print?

Python

result = {x: ('even' if x % 2 == 0 else 'odd') for x in range(4)}
print(result)

A {0: 'even', 1: 'odd', 2: 'even', 3: 'odd'}

B {0: 'odd', 1: 'even', 2: 'odd', 3: 'even'}

C {0: True, 1: False, 2: True, 3: False}

D TypeError

💡 Hint

Check how the ternary operator assigns values based on even or odd keys.

The ternary expression assigns 'even' if x is divisible by 2, else 'odd'.

❓ 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(2)} for x in range(3)}
print(result)

A {0: {0: 0, 1: 0}, 1: {0: 0, 1: 1}, 2: {0: 0, 1: 2}}

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

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

D SyntaxError

💡 Hint

Look carefully at the inner dictionary comprehension and how multiplication works.

For each x, the inner dictionary maps y to x*y for y in 0 and 1.

❓ Predict Output

advanced

Result of dictionary comprehension with string keys

What will this code output?

Python

keys = ['a', 'b', 'c']
result = {k: ord(k) for k in keys}
print(result)

A TypeError

B {'a': 97, 'b': 98, 'c': 99}

C {'a': 'a', 'b': 'b', 'c': 'c'}

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

💡 Hint

The ord() function returns the Unicode code point of a character.

Each key maps to its Unicode number using ord().

🧠 Conceptual

expert

Number of items in dictionary comprehension result

How many items are in the dictionary created by this comprehension? {n: n//2 for n in range(10) if n % 3 != 0}

A 3

B 7

C 10

D 6

💡 Hint

Count numbers from 0 to 9 excluding multiples of 3.

Numbers 0,3,6,9 are multiples of 3 and excluded. Remaining 6 numbers create 6 items.