input: Write a function to find the second largest number in a list.
  assert second_largest([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==9
  assert second_largest([10, 20, 45, 67, 84, 93])==84
  assert second_largest([5, 7, 9, 8, 6, 4, 3])==8
output: def second_largest(numbers):
      first = second = float('-inf')
      for number in numbers:
          if number > first:
              second = first
              first = number
          elif first > number > second:
              second = number
      return second