#!/usr/bin/env python3 # -*- coding: utf-8 -*- def fact(n): if n == 1: return 1 return n * fact(n - 1) def fact(n): return factIter(n, 1) def factIter(num, product): if num == 1: return product return factIter(num - 1, num * product) L = ['Michael', 'Sarach', 'Tracy', 'Bob', 'Jack'] >>> L = ['Michael', 'Sarach', 'Tracy', 'Bob', 'Jack'] >>> >>> L ['Michael', 'Sarach', 'Tracy', 'Bob', 'Jack'] >>> L[0:3] ['Michael', 'Sarach', 'Tracy'] >>> L[:3] ['Michael', 'Sarach', 'Tracy'] >>> L[1:3] ['Sarach', 'Tracy'] >>> L[-2:] ['Bob', 'Jack'] >>> L = list(range(100)) >>> L [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 2 2, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 4 2, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 6 2, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 8 2, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99] >>> L[:10] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> L[-10:] [90, 91, 92, 93, 94, 95, 96, 97, 98, 99] >>> L[10:20] [10, 11, 12, 13, 14, 15, 16, 17, 18, 19] >>> L[:10:2] [0, 2, 4, 6, 8] >>> L[::5] [0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95] >>> L[:] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 2 2, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 4 2, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 6 2, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 8 2, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99] >>> (0, 1, 2, 3, 4, 5)[:3] (0, 1, 2) >>> 'ABCDEFG'[:3] 'ABC' >>> 'ABCDEFG'[::2] 'ACEG' list = [1,2,3,4,5] list[:3] #输出[1,2,3] list[0:3] #输出[1,2,3] list[-2:] #输出[4.5] list[-2:-1] #输出[4] 可以通过定义来理解。假想一个不存在的下标-0,用正数表示时指0之前的元素,用负数表示时指-1后的一个元素,但他们实际是不存在的。 list[:3] == list[-0:3]:虽然切片list[-0:3]包含-0元素,但其实他不存在,所以与list[0:3]相等。 list[-2:] == list[-2:-0]:切片list[-2:-0]不包含-0元素,他实际也不存在,所以不包含在此处没起作用,list[-2:-1]中的-1是存在的,所以不包含起作用了,故此两者不相等。