Lists and Data

Start with a list of two tracks. Use append() for each new entry and enumerate(playlist, start=1) when listing.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 41 - Build a Playlist
playlist = ["Night Drive", "Sunrise Beat"]
added = 0
while added < 3:
    song = input("Add a song: ").strip()
    if not song:
        print("Please enter a song title.")
        continue
    playlist.append(song)
    added += 1
for position, song in enumerate(playlist, start=1):
    print(f"{position}. {song}")

Before adding, compare casefold() versions of each item. Before calling remove(), locate an existing match.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 42 - Tidy a Shopping List
items = ["bread", "milk", "apples"]
new_item = input("Add an item (blank to skip): ").strip()
if new_item:
    if new_item.casefold() in [item.casefold() for item in items]:
        print("Item already listed.")
    else:
        items.append(new_item)
remove_item = input("Remove an item (blank to skip): ").strip()
if remove_item:
    found = next((item for item in items
                  if item.casefold() == remove_item.casefold()), None)
    if found is None:
        print("Item not found.")
    else:
        items.remove(found)
for number, item in enumerate(items, start=1):
    print(f"{number}. {item}")

Use sum(marks) / len(marks) only when the list is not empty. Format the result with :.2f.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 43 - Average Test Marks
marks = [70, 80, 90, 60]
if marks:
    average = sum(marks) / len(marks)
    print(f"Average: {average:.2f}")
else:
    print("No marks to average.")

Use max() to find the best score. Look through all pairs to collect every name sharing that score.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 44 - Leaderboard Leader
results = [("Alex", 18), ("Bea", 22), ("Chen", 22), ("Dee", 15)]
if not results:
    print("No scores yet.")
else:
    top_score = max(score for name, score in results)
    winners = [name for name, score in results if score == top_score]
    if len(winners) == 1:
        print(f"Winner: {winners[0]} ({top_score})")
    else:
        print(f"Tie: {', '.join(winners)} ({top_score})")

Make an empty unique_scores list; append each value only once, then use sorted(..., reverse=True) [:3].

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 45 - Sort the Results
scores = [18, 12, 18, 26, 25, 26, 12, 24]
unique_scores = []
for score in scores:
    if score not in unique_scores:
        unique_scores.append(score)
top_three = sorted(unique_scores, reverse=True)[:3]
print("Top distinct scores:", top_three)
print("Original scores:", scores)

A simple name in register check is case-sensitive. Remember to strip spaces first.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 46 - Who's on the Register?
register = ["Amira", "Bella", "Chen", "Daniel"]
name = input("First name to check: ").strip()
if name in register:
    print(f"Registered: {name}")
else:
    print(f"Not registered: {name}")

Use .strip() on new input. Compare .casefold() versions of the new and stored names.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 47 - No Duplicate Names
register = ["Sam", "Alex", "Rory"]
name = input("Add a name: ").strip()
if not name:
    print("Please enter a name.")
elif name.casefold() in [person.casefold() for person in register]:
    print("Duplicate name: not added.")
else:
    register.append(name)
    print(f"Added: {name}")
print("Register:", ", ".join(register))

Keep a count for each candidate. Increase the matching position; after counting, find all tied leaders.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 48 - Count the Votes
candidates = ["Ava", "Ben", "Cara"]
ballots = ["Ava", "Ben", "Ava", "Cara", "Ben", "Ava"]
counts = [0] * len(candidates)
for ballot in ballots:
    if ballot in candidates:
        counts[candidates.index(ballot)] += 1
for index, candidate in enumerate(candidates):
    print(f"{candidate}: {counts[index]}")
print(f"Valid ballots: {sum(counts)}")
if not candidates or sum(counts) == 0:
    print("No valid votes.")
else:
    best = max(counts)
    leaders = [candidates[i] for i in range(len(candidates))
               if counts[i] == best]
    print(("Winner: " if len(leaders) == 1 else "Tie: ")
          + ", ".join(leaders))

Try names[::2] for positions 0, 2, 4... and names[1::2] for positions 1, 3, 5...

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 49 - Make Balanced Teams
names = ["Alex", "Bea", "Chen", "Dee", "Eli"]
team_a = names[::2]
team_b = names[1::2]
print("Team A:", ", ".join(team_a) if team_a else "none")
print("Team B:", ", ".join(team_b) if team_b else "none")

Confirm a number was entered, then check it is in the valid range before using position - 1 as the index.

One possible implementation. Check the book's tests and try an extension after comparing.

# Challenge 50 - The Wrong List Item
colours = ["red", "blue", "green", "yellow", "purple"]
position_text = input("Choose a position (1-5): ").strip()
if not position_text.isdigit():
    print("Enter a whole number from 1 to 5.")
else:
    position = int(position_text)
    if 1 <= position <= len(colours):
        print(f"Item: {colours[position - 1]}")
    else:
        print("Position must be from 1 to 5.")