Save High Score

🎯 Learning Objectives

• Use open() with modes "r" and "w" to read and write text files
• Handle FileNotFoundError with try / except
• Use f-strings to format strings with embedded values
• Build a simple leaderboard using a dictionary

💡 The Big Idea — Annotated Code

SCORE_FILE = "high_score.txt"

# ── Load high score from file ──
try:
    with open(SCORE_FILE, "r") as f:
        high_score = int(f.read().strip())  # strip() removes newline
except FileNotFoundError:
    high_score = 0   # first time running — file doesn't exist yet
except ValueError:
    high_score = 0   # file exists but content is not an integer

# ── Save high score to file ──
def save_score(score, high_score):
    if score > high_score:
        high_score = score
        with open(SCORE_FILE, "w") as f:
            f.write(str(high_score))
    return high_score

# ── f-string formatting ──
name = "Nurul"
score = 42
print(f"Player: {name} — Score: {score:04d}")  # → "Player: Nurul — Score: 0042"
pygame.display.set_caption(f"Snake — Score: {score}  Best: {high_score}")

# ── Leaderboard (dictionary) ──
leaderboard = {}   # {"PlayerName": best_score}

def update_leaderboard(name, score):
    if name not in leaderboard or score > leaderboard[name]:
        leaderboard[name] = score

Key concept explanations

• with open(path, mode) as f: — the with statement ensures the file is closed even if an error occurs. "r" = read, "w" = write (overwrites), "a" = append.
• try / except — try runs code that might fail; except ExceptionType: catches a specific error type. Always catch the most specific exception you can.
• FileNotFoundError — raised when open() is called on a file that doesn't exist. Common in file I/O — always handle it.
• .strip() — removes leading/trailing whitespace including (newline). A file read with f.read() often ends with a newline.
• f-strings f"..." — embed expressions directly in strings with {variable}. {score:04d} formats as a 4-digit integer with leading zeros.

🔢 Activity Answers

Tier 1 — Check Understanding

Tier 2 — Fix the Bug

Bug: high_score = int(f.read()) without .strip() — crashes if file has a trailing newline.

Error: ValueError: invalid literal for int() with base 10: '42 '

Fix: high_score = int(f.read().strip())

Tier 3 — Extend: Save the leaderboard to a CSV file

import csv

def save_leaderboard(leaderboard, filename="leaderboard.csv"):
    with open(filename, "w", newline="") as f:
        writer = csv.writer(f)
        writer.writerow(["Name", "Score"])
        for name, score in sorted(leaderboard.items(), key=lambda x: -x[1]):
            writer.writerow([name, score])

def load_leaderboard(filename="leaderboard.csv"):
    scores = {}
    try:
        with open(filename, "r") as f:
            reader = csv.DictReader(f)
            for row in reader:
                scores[row["Name"]] = int(row["Score"])
    except FileNotFoundError:
        pass
    return scores

Tier 4 — New Task: Ask the player's name at game over and add to leaderboard

import pygame
# After running = False (game over):
pygame.event.clear()
font = pygame.font.SysFont("monospace", 24)
player_name = ""
asking = True
while asking:
    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_RETURN:
                asking = False
            elif event.key == pygame.K_BACKSPACE:
                player_name = player_name[:-1]
            elif len(player_name) < 10:
                player_name += event.unicode
    screen.fill(BG)
    prompt = font.render(f"Enter name: {player_name}_", True, WHITE)
    screen.blit(prompt, (20, WINDOW_H // 2))
    pygame.display.flip()

if player_name:
    update_leaderboard(player_name, score)
    save_leaderboard(leaderboard)

Reflective Journal — Suggested Strong Answers

⚠️ Mistakes Students Actually Make

🗣️ Teaching & Facilitation Notes

Opening hook

"What happens to your high score if the power goes out?" For students who've played arcade games, this is intuitive. File I/O is how software remembers things beyond a single session.

Motivating try/except

Before explaining it, ask students to delete high_score.txt (or pretend they're running for the first time) and run the code without the try/except. They'll see the crash. Now add try/except and show it works. Failure first, solution second — the most memorable teaching sequence.

The "with" statement

Emphasise that with open(...) as f: automatically closes the file. Without it, forgetting f.close() can cause data loss or file locks. "It's like a responsible borrower — it returns the book before walking out the door."

f-strings vs % formatting

Some students may have seen "Score: %d" % score in older tutorials. f-strings are the modern, readable standard — steer students toward them.

CT connection — Persistence