input: 
  def find_max(list):
      max_num = 0
      for i in list:
          if i > max_num:
              max_num = i
      return max_num
  
  # Test cases
  print(find_max([1, 3, 12, 5, 8, 10])) # Should print 12
  print(find_max([0, 0, 0, 0]))         # Should print 0
  print(find_max([4, 7, 1, 9, 2]))      # Should print 9
  print(find_max([100]))                # Should print 100
  
output:     if not list:
          return None
      max_num = list[0]
      for i in list:
          if i > max_num:
              max_num = i
      return max_num