li = [1, 4, 5, 6, 7, 9, 11, 14, 16]

# 以下写法都可以表示整个列表，其中 X >= len(li)
li[0:X] == li[0:] == li[:X] == li[:] == li[::] == li[-X:X] == li[-X:]

li[1:5] == [4,5,6,7] # 从1起，取5-1位元素
li[1:5:2] == [4,6] # 从1起，取5-1位元素，按2间隔过滤
li[-1:] == [16] # 取倒数第一个元素
li[-4:-2] == [9, 11] # 从倒数第四起，取-2-(-4)=2位元素
li[:-2] == li[-len(li):-2] == [1,4,5,6,7,9,11] # 从头开始，取-2-(-len(li))=7位元素

# 步长为负数时，列表先翻转，再截取
li[::-1] == [16,14,11,9,7,6,5,4,1] # 翻转整个列表
li[::-2] == [16,11,7,5,1] # 翻转整个列表，再按2间隔过滤
li[:-5:-1] == [16,14,11,9] # 翻转整个列表，取-5-(-len(li))=4位元素
li[:-5:-3] == [16,9] # 翻转整个列表，取-5-(-len(li))=4位元素，再按3间隔过滤

# 切片的步长不可以为0
li[::0] # 报错（ValueError: slice step cannot be zero）

li = [1, 2, 3, 4]
ls = li[::]

li == ls # True
id(li) == id(ls) # False
li.append(li[2:4]) # [1, 2, 3, 4, [3, 4]]
ls.extend(ls[2:4]) # [1, 2, 3, 4, 3, 4]

# 下例等价于判断li长度是否大于8
if(li[8:]):
  print("not empty")
else:
  print("empty")

# 切片列表受制于原列表
lo = [1,[1,1],2,3]
lp = lo[:2] # [1, [1, 1]]
lo[1].append(1) # [1, [1, 1, 1], 2, 3]
lp # [1, [1, 1, 1]]

li = [1, 2, 3, 4]

# 在头部拼接
li[:0] = [0] # [0, 1, 2, 3, 4]
# 在末尾拼接
li[len(li):] = [5,7] # [0, 1, 2, 3, 4, 5, 7]
# 在中部拼接
li[6:6] = [6] # [0, 1, 2, 3, 4, 5, 6, 7]

# 给切片赋值的必须是可迭代对象
li[-1:-1] = 6 # （报错，TypeError: can only assign an iterable）
li[:0] = (9,) # [9, 0, 1, 2, 3, 4, 5, 6, 7]
li[:0] = range(3) # [0, 1, 2, 9, 0, 1, 2, 3, 4, 5, 6, 7]

li = [1, 2, 3, 4]

# 不同位置的替换
li[:3] = [7,8,9] # [7, 8, 9, 4]
li[3:] = [5,6,7] # [7, 8, 9, 5, 6, 7]
li[2:4] = ['a','b'] # [7, 8, 'a', 'b', 6, 7]

# 非等长替换
li[2:4] = [1,2,3,4] # [7, 8, 1, 2, 3, 4, 6, 7]
li[2:6] = ['a'] # [7, 8, 'a', 6, 7]

# 删除元素
del li[2:3] # [7, 8, 6, 7]

li = [1, 2, 3, 4, 5, 6]

li[::2] = ['a','b','c'] # ['a', 2, 'b', 4, 'c', 6]
li[::2] = [0]*3 # [0, 2, 0, 4, 0, 6]
li[::2] = ['w'] # 报错，attempt to assign sequence of size 1 to extended slice of size 3

del li[::2] # [2, 4, 6]