Well done! It's time to wrap things up. Let's summarize what we've learned before we take the quiz.

1. Use a for loop to iterate over a list. You may need one or more variables defined before the loop.

   numbers = [2, 45, 32, 1]
   sum = 0
   for number in numbers:
     sum += number

2. You can usethe enumerate() function with a for loop.

   first_sum = 0
   second_sum = 0
   for i, number in enumerate(numbers):
     if i < 2:
       first_sum += number
     else:
       second_sum += number
   

3. If you want to update list elements, iterate over the indexes.

   for i in range(len(numbers)):
     numbers[i] = ...

4. To change the element order, iterate over the indexes.

   for i in range(0, len(numbers), 2):
     numbers[i], numbers[i+1] = numbers[i+1], numbers[i]
   

5. To safely delete list elements, iterate over a copy of the list using [:].

   for number in numbers[:]:
     numbers.remove(number)

6. When creating a new list based on an existing one, you will typically need an empty list before the loop with an append() function inside it.

   neg_numbers = []
   for number in numbers:
     neg_numbers.append(-1 * number)

7. To compare two same-sized lists element by element, iterate over the indexes of either list.

   numbers1 = [4, 98, 23, 43]
   numbers2 = [2, 45, 32, 1]
   for i in range (len(numbers1)):
     if numbers1[i] > numbers2[i]:
       ...

8. When comparing two lists with different sizes, watch out for IndexErrors: iterate over the shorter list or check if the current index is within the bounds.

   numbers1 = [2, 45]
   numbers2 = [2, 45, 32, 1]

   • iterate over the shorter list

     for i in numbers1:
       ...

   • check the index inside

     for i in numbers2:
       if i < len(numbers1):
         ...

9. When merging sorted lists or searching for common elements, you will typically need a while loop and two variables to store the current list indexes.

   i, j = 0, 0
   while i < len(list1) and j < len(list2):
     if ...: i += 1
     if ...: j += 1

Quite a lot! All right, it's time for a short quiz.