8、基本数据类型---列表

#方法一
L1 = [] #定义空列表
L2 = [‘a‘,‘b‘,‘c‘,‘d‘] #存4个值，索引为0-3
L3 = [‘abc‘,[‘def‘,‘ghi‘]] #嵌套列表

#方法二
L4 = list()

>>> L2 = [‘a‘,‘b‘,‘c‘,‘d‘,‘a‘,‘e‘,1,2]
>>> L2[2]#通过索引取值
‘c‘
>>> L2[-1]#通过索引从列表右边开始取值
2
>>> L2[-2]
1
>>> L2.index(‘a‘)#返回指定元素的索引值，从左右查找，找到第一个匹配值，则返回
0
>>> L2.count(‘a‘)#统计指定元素的个数
2

>>> L2 = [‘a‘,‘b‘,‘c‘,‘d‘,‘a‘,‘e‘,1,2]
>>> L2[0:3]#返回从索引0至3的元素，不包括3，顾头不顾尾
[‘a‘, ‘b‘, ‘c‘]
>>> L2[0:-1]#返回从索引0至最后一个值，不包括最后一个值
[‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘a‘, ‘e‘, 1]
>>> L2[3:6]#返回从索引3至6的元素
[‘d‘, ‘a‘, ‘e‘]
>>> L2[3:]#返回从索引3至最后所有的值
[‘d‘, ‘a‘, ‘e‘, 1, 2]
>>> L2[:3]#返回从0至3的值
[‘a‘, ‘b‘, ‘c‘]
>>> L2[1:6:2]#返回索引1至6的值，但是步长为6（每隔一个值，取一个值）
[‘b‘, ‘d‘, ‘e‘]
>>> L2[:]#返回所有的值
[‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘a‘, ‘e‘, 1, 2]
>>> L2[::2]#按步长为2，返回所有的值
[‘a‘, ‘c‘, ‘a‘, 1]

>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘a‘, ‘e‘, 1, 2]
>>> L2.append(‘A‘)#列表最后面追加A
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘a‘, ‘e‘, 1, 2, ‘A‘]
>>> L2.insert(3,‘B‘)#在列表的索引为3的位置，插入一个值B
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘B‘, ‘d‘, ‘a‘, ‘e‘, 1, 2, ‘A‘]

L2
[‘a‘, ‘b‘, ‘c‘, ‘B‘, ‘d‘, ‘a‘, ‘e‘, 1, 2, ‘A‘]
>>> L2[3] = ‘Boy‘#把索引3的元素修改为Boy
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘d‘, ‘a‘, ‘e‘, 1, 2, ‘A‘]
>>> L2[4:6] = ‘ALEX LI‘#把索引4-6的元素改为ALEX LI,不够元素自动增加
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘A‘, ‘L‘, ‘E‘, ‘X‘, ‘ ‘, ‘L‘, ‘I‘, ‘e‘, 1, 2, ‘A‘]

L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘A‘, ‘L‘, ‘E‘, ‘X‘, ‘ ‘, ‘L‘, ‘I‘, ‘e‘, 1, 2, ‘A‘]
>>> L2.pop()#删除最后一个元素
‘A‘
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘A‘, ‘L‘, ‘E‘, ‘X‘, ‘ ‘, ‘L‘, ‘I‘, ‘e‘, 1, 2]
>>> L2.remove(‘L‘)#删除从左找到的第一个指定元素
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘A‘, ‘E‘, ‘X‘, ‘ ‘, ‘L‘, ‘I‘, ‘e‘, 1, 2]
>>> del L2[4]#用python的全局的删除方法删除指定元素
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘Boy‘, ‘E‘, ‘X‘, ‘ ‘, ‘L‘, ‘I‘, ‘e‘, 1, 2]
>>> del L2[3:7]#删除多个元素
>>> L2
[‘a‘, ‘b‘, ‘c‘, ‘L‘, ‘I‘, ‘e‘, 1, 2]

L2 = [‘a‘,‘b‘,‘c‘,‘d‘,‘a‘,‘e‘,1,2]
for i in L2:
    print(i)

>>> L2 = [‘a‘,‘b‘,‘A‘,‘C‘,‘#‘,‘!‘,1,2]
>>> L2.sort()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>#不能对包含了str和int的列表进行排序
TypeError: ‘<‘ not supported between instances of ‘int‘ and ‘str‘
>>> L2 = [‘a‘,‘b‘,‘A‘,‘C‘,‘#‘,‘!‘]
>>> L2.sort()
>>> L2
[‘!‘, ‘#‘, ‘A‘, ‘C‘, ‘a‘, ‘b‘]
>>> L2.reverse()#反转
>>> L2
[‘b‘, ‘a‘, ‘C‘, ‘A‘, ‘#‘, ‘!‘]

>>> L2
[‘b‘, ‘a‘, ‘C‘, ‘A‘, ‘#‘, ‘!‘]
>>> L2.extend([1,2,3,4])#把一个列表，扩展到L2列表
>>> L2
[‘b‘, ‘a‘, ‘C‘, ‘A‘, ‘#‘, ‘!‘, 1, 2, 3, 4]
>>> L2[2] = [‘Alex‘,‘Jack‘,‘Rain‘]
>>> L2
[‘b‘, ‘a‘, [‘Alex‘, ‘Jack‘, ‘Rain‘], ‘A‘, ‘#‘, ‘!‘, 1, 2, 3, 4]
>>> L2[2][2]#嵌套列表取值
‘Rain‘
>>> L2.clear()#清空列表
>>> L2
[]
>>> L2.copy()#后面详细分析