Exercises — Dictionaries

Exercise 4.4.1 Beginner

Given a list of words, return a dictionary mapping each word to its length.

words = ["apple", "banana", "cherry", "date"]
# expected: {"apple": 5, "banana": 6, "cherry": 6, "date": 4}

▶ Try in Playground

Exercise 4.4.2 Beginner

Given two dictionaries, return a new dictionary that merges them. If a key appears in both, the value from the second dict wins.

a = {"x": 1, "y": 2}
b = {"y": 99, "z": 3}
# expected: {"x": 1, "y": 99, "z": 3}

▶ Try in Playground

Exercise 4.4.3 Intermediate

Given a list of strings, use defaultdict to group them by their first character.

words = ["apple", "avocado", "banana", "blueberry", "cherry"]
# expected: {"a": ["apple", "avocado"], "b": ["banana", "blueberry"], "c": ["cherry"]}

▶ Try in Playground

Exercise 4.4.4 Intermediate

Given a sentence, use Counter to find the three most common characters (ignoring spaces).

sentence = "the quick brown fox jumps over the lazy dog"
# expected: something like [("o", 4), ("e", 3), ("t", 2)]
# (exact result depends on the sentence)

▶ Try in Playground

Exercise 4.4.5 Intermediate

Given a dictionary mapping student names to lists of grades, return a new dictionary mapping each student to their average grade, rounded to one decimal place.

grades = {
    "Alice": [90, 85, 92],
    "Bob":   [70, 75, 80],
    "Carol": [88, 95, 91],
}
# expected: {"Alice": 89.0, "Bob": 75.0, "Carol": 91.3}

▶ Try in Playground

Exercise 4.4.6 Advanced

Given a list of dictionaries representing transactions, return a summary dict that maps each category to the total amount spent in that category.

transactions = [
    {"category": "food",      "amount": 12.5},
    {"category": "transport", "amount": 3.0},
    {"category": "food",      "amount": 8.0},
    {"category": "books",     "amount": 25.0},
    {"category": "transport", "amount": 2.5},
]
# expected: {"food": 20.5, "transport": 5.5, "books": 25.0}

▶ Try in Playground