Lesson 5.4: Debugging Game Bugs

Today’s Goals

• Learn how to read and fix error messages
• Practice debugging strategies on Hangman
• Build confidence in fixing broken code

Warm-Up Question

• When your code breaks, what’s the first thing you do?
• (Call on 2–3 students)

Debugging Strategies

• Read the error message carefully
• Check the line number Python gives you
• Trace values with print() statements
• Test one change at a time

Buggy Hangman Example

word = "python"
blanks = ["_"] * len(word)

for i in range(len(word)):
    if word[i] = guess:   #  bug here
        blanks[i] == guess

print(" ".join(blanks))

Class Practice

• Copy the buggy code
• What error shows up?
• How can we fix it?

Another Buggy Example

word = "python"
guess = input("Guess a letter: ")

if guess.isalpha():
    print("Good guess!")
else:
    print("Invalid input!")

if guess in word:
    print("Yes!")
print("You guessed right!")   #  always prints

Discussion

• Why does the last line always print?
• How could we fix this?

Student Challenge

• Fix at least 3 different bugs in provided Hangman snippets
• For each bug:
  • Write the error message
  • Explain what caused it
  • Show the corrected code

Wrap-Up

• Debugging is about careful reading and testing
• Next time: We’ll build full Hangman with groups