Find and Fix Mistakes in Python Lists – Practice Debugging Exercises

Boost your Python skills by identifying and correcting common mistakes in list operations. Practice debugging Python list syntax, indexing errors, and method misuse with hands-on examples.

Topic: lists

🧪 Fix & Find Questions

🟢 Beginner Fix & Find

1. Fix the list creation error:

   fruits = ['apple', 'banana', 'orange']
   print(fruits[3])
   

   Hint: 💡 Remember how list indexing works in Python.

   🔍 View Issue & Fixed Solution

   Issue: Trying to access an index that's out of range.

   ✅ Fixed Solution

   fruits = ['apple', 'banana', 'orange']
   print(fruits[2])  # Last element is at index 2 (0-based indexing)
   

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2. Fix the list element removal:

   colors = ['red', 'green', 'blue']
   colors.remove('yellow')
   print(colors)
   

   Hint: 💡 What happens when removing a non-existent element?

   🔍 View Issue & Fixed Solution

   Issue: Trying to remove an element that doesn't exist in the list.

   ✅ Fixed Solution

   colors = ['red', 'green', 'blue']
   if 'yellow' in colors:
       colors.remove('yellow')
   print(colors)  # Now won't raise ValueError
   

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🟡 Intermediate Fix & Find

1. Fix the list slicing operation:

   numbers = [0, 1, 2, 3, 4, 5]
   middle = numbers[2:4]
   print(middle[-1])  # Should print 4
   

   Hint: 💡 Check the slice end index and negative indexing.

   🔍 View Issue & Fixed Solution

   Issue: The slice doesn't include the desired last element.

   ✅ Fixed Solution

   numbers = [0, 1, 2, 3, 4, 5]
   middle = numbers[2:5]  # or numbers[2:]
   print(middle[-1])  # Now correctly prints 4
   

   ---

2. Fix the list method usage:

   items = [1, 2, 3]
   items.append([4, 5])
   print(items)  # Should show [1, 2, 3, 4, 5]
   

   Hint: 💡 Check the difference between append() and extend().

   🔍 View Issue & Fixed Solution

   Issue: append() adds the entire list as a single element.

   ✅ Fixed Solution

   items = [1, 2, 3]
   items.extend([4, 5])  # or items += [4, 5]
   print(items)  # Now correctly shows [1, 2, 3, 4, 5]
   

   ---

🔴 Advanced Fix & Find

1. Fix the list reverse operation:

   values = [10, 20, 30, 40]
   reversed_values = values.reverse()
   print(reversed_values)  # Should print [40, 30, 20, 10]
   

   Hint: 💡 Remember that some list methods modify in-place and return None.

   🔍 View Issue & Fixed Solution

   Issue: reverse() modifies the list in-place and returns None.

   ✅ Fixed Solution

   # Solution 1: Use the method then print the original
   values = [10, 20, 30, 40]
   values.reverse()
   print(values)
   
   # Solution 2: Use slicing to create a reversed copy
   values = [10, 20, 30, 40]
   reversed_values = values[::-1]
   print(reversed_values)
   

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