split()返回的是一个列表,所以中括号是他的访问索引。把split()看成列表就好理解了
lst = [‘a’, ‘b’ , ‘c’] lst[0] ‘a’ lst[-1] ‘c’
lst = [‘a’, ‘b’ , ‘c’] lst[0] ‘a’
lst[-1] ‘c’