find the second largest number in a list

1def second_largest(numbers):
2  if (len(numbers)<2):
3    return
4  if ((len(numbers)==2)  and (numbers[0] == numbers[1]) ):
5    return
6  dup_items = set()
7  uniq_items = []
8  for x in numbers:
9    if x not in dup_items:
10      uniq_items.append(x)
11      dup_items.add(x)
12  uniq_items.sort()    
13  return  uniq_items[-2]   
14print(second_largest([1,2,3,4,4]))
15print(second_largest([1, 1, 1, 0, 0, 0, 2, -2, -2]))
16print(second_largest([2,2]))
17print(second_largest([1]))
18
19