Level 3Exercise #56

Group words by first letter

Group words by their lowercase first letter while preserving order.

What you’ll practice

This Level 3 exercise focuses on defaultdict(list) in the Collections curriculum. Solve the challenge prompt above using clear, idiomatic Python and the relevant language or standard-library tools.

Relevant Python reference: collections.defaultdict.

Sample Test Cases

Example #1

Input:by_initial(['API','agent','cache'])

Output:{'a':['API','agent'],'c':['cache']}

Reference Solution

Reveal Reference Solution

def by_initial(words: list[str]) -> dict[str, list[str]]:
    from collections import defaultdict
    groups = defaultdict(list)
    for word in words:
        groups[word[0].lower()].append(word)
    return dict(groups)

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Group words by first letter

What you’ll practice

Sample Test Cases

Further Reading

Reference Solution