pythonLogic errorEasy

Itertools groupby on unsorted list splits identical keys

Time: 0:00

BugFind the bug and fix the code

What it should do

extract_grouped_keys(items) returns the unique sorted group keys from items. Example: extract_grouped_keys(["a", "b", "a"]) → ["a", "b"].

What happens instead

extract_grouped_keys(["a", "b", "a"]) returns ["a", "b", "a"] with duplicate group keys.

from itertools import groupby

def extract_grouped_keys(items):
    return [k for k, g in groupby(items)]

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

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Think & Test Cooldown

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Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

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Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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pythonLogic errorEasy

Itertools groupby on unsorted list splits identical keys

Time: 0:00

BugFind the bug and fix the code

What it should do

extract_grouped_keys(items) returns the unique sorted group keys from items. Example: extract_grouped_keys(["a", "b", "a"]) → ["a", "b"].

What happens instead

extract_grouped_keys(["a", "b", "a"]) returns ["a", "b", "a"] with duplicate group keys.

from itertools import groupby

def extract_grouped_keys(items):
    return [k for k, g in groupby(items)]

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Think & Test Cooldown

2:00 remaining

Take a moment to read the bug symptom and trace the code with Run & Check before unlocking Hint 1.

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

Itertools groupby on unsorted list splits identical keys

What it should do

What happens instead

More logic errors to practise

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Itertools groupby on unsorted list splits identical keys

What it should do

What happens instead

More logic errors to practise

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