Functions can also take lists as inputs and perform various operations on those lists.

def count_small(numbers):
  total = 0
  for n in numbers:
    if n < 10:
      total = total + 1
  return total

lotto = [4, 8, 15, 16, 23, 42]
small = count_small(lotto)
print small

1. In the above example, we define a function count_small that has one parameter, numbers.
2. We initialize a variable total that we can use in the for loop.
3. For each item n in numbers, if n is less than 10, we increment total.
4. After the for loop, we return total.
5. After the function definition, we create an array of numbers called lotto.
6. We call the count_small function, pass in lotto, and store the returned result in small.
7. Finally, we print out the returned result, which is 2 since only 4 and 8 are less than 10.