Python Practice Problems

A focused problem isolates one concept, so that when you get it wrong you know what to review. The four problems here each target a different skill:

An oversized task, such as "build a radio scheduling app", mixes so many skills that a failure tells you little. Small problems also give quick feedback, which keeps practice sessions productive. Do one or two focused problems a day rather than a long session once a week; spacing practice out helps you remember it.

For each problem, the reasoning that connects the question to the code matters more than the final lines. Here is problem 1 worked through:

1. Restate: convert minutes and seconds into total seconds, rejecting impossible values.
2. Rules: minutes can't be negative; seconds must be 0 to 59, since 60 seconds would be another minute.
3. Method: total = minutes × 60 + seconds.
4. Check by hand: 4 min 25 s → 240 + 25 = 265.
5. Edge cases: 0 min 0 s → 0; 0 min 59 s → 59; 1 min 60 s → error.

for args in [(0, 0), (0, 59), (1, 60)]:
    try:
        print(args, broadcast_seconds(*args))
    except ValueError as error:
        print(args, "->", error)

Code shown without reasoning encourages memorising lines rather than understanding choices. When you write your own solutions, write steps like these as comments first, then fill in the code beneath each one.

Attempt each problem before looking at the answer, and write down a prediction or plan, even if you're unsure. Struggling briefly to recall and apply an idea, called retrieval practice, is what strengthens memory; reading a solution straight away feels productive but leaves little behind.

A simple routine:

1. Read the problem and write your plan in comments.
2. Write the code and run your own test cases.
3. If a test fails, explain why in one sentence before changing anything.
4. Only then compare with the worked answer, noting any difference in approach.

If you're stuck for more than about fifteen minutes, read just the first step of the worked reasoning, then try again. Hints in the course exercises work the same way: open the hint before the solution.

After solving a problem, apply the same idea to a different situation. Problem 1's duration logic transfers to rehearsal schedules, cooking timers and video timestamps:

def rehearsal_minutes(hours, minutes):
    if hours < 0 or not 0 <= minutes < 60:
        raise ValueError("Invalid rehearsal length")
    return hours * 60 + minutes

Transfer is the real test of understanding. Renaming variables isn't transfer; noticing that the same rule ("units must be in range, then combine with a multiplier") applies, and checking whether its assumptions still hold, is. For example, a timestamp 1:05:30 adds an hours unit, so the function needs a third parameter and range check.

When a transferred version fails, compare it with the original: the difference usually reveals an assumption you hadn't noticed.

Task: solve duration conversion, frequency counting, validated CSV totals and independent object state problems with written reasoning. Try these variations without looking back:

# 1. Extend broadcast_seconds to accept hours, minutes and seconds.
# 2. Return the single least played track, ties broken alphabetically.
# 3. Total CSV minutes per show type, where a 'type' column is added.
# 4. Give Playlist a remove(track) method that ignores missing tracks.

def broadcast_seconds(hours, minutes, seconds):
    if hours < 0 or not 0 <= minutes < 60 or not 0 <= seconds < 60:
        raise ValueError("Invalid duration")
    return hours * 3600 + minutes * 60 + seconds

print(broadcast_seconds(1, 5, 30))    # 3930

The first variation is solved as a model; write reasoning comments for the other three before coding them. For the worked check, you attempt a problem before reading its solution to expose your current reasoning and gaps.

Work through the interactive Python exercises, filtering by chapter and difficulty, and the Python quiz. Continue with exercises by difficulty and beginner projects.