python找出列表中的连续元素

比如： 
[3,4,5,6,7,10,11,12,15,16,17,19,20,21,22,23,24,42,43,44,45,46,48] 
怎么得到下面的结果呢？ 
[[3,7],[10,12],[15,17],[19,24],[42,46],[48,48]]

解答代码：

>>> a = [3,4,5,6,7,10,11,12,15,16,17,19,20,21,22,23,24,42,43,44,45,46,48]
>>> t1 = []
>>> t2 = []
>>> for x in a:
    t1.append(x)
    if x+1 not in a:
        t2.append([t1[0], t1[-1]])
        print(t1[0],t1[-1])
        t1 = []

        
3 7
10 12
15 17
19 24
42 46
48 48
>>> t2
[[3, 7], [10, 12], [15, 17], [19, 24], [42, 46], [48, 48]]
>>>