序列包括字符串，列表，元祖，序列中的每个元素都有编号，其中只有元祖不能修改
通用序列操作包括索引、 切片、 相加、 相乘和成员资格检查
索引
>>> greeting = 'Hello'
>>> greeting[0]
'H'
>>> greeting[-1]
'o'
>>> 'Hello'[1]
'e'
>>> fourth = input('Year: ')[3]
Year: 2005
>>> fourth
'5'
切片
>>> tag = '<a href="http://www.python.org">Python web site</a>'
>>> tag[9:30]
>>> tag[32:-4]
'Python web site'
>>> numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> numbers[3:6] [4, 5, 6]
>>> numbers[0:1] [1]
开始元素包括结尾元素不包括
>>> numbers[-3:-1]
[8, 9]
>>> numbers[-3:0]
【】
>>> numbers[-3:]
[8, 9, 10]
>>> numbers[:3]
[1, 2, 3]
>>> numbers[:]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
第三位为步长
>>> numbers[0:10:1]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> numbers[0:10:2]
[1, 3, 5, 7, 9]
numbers[3:6:3]
[4]
>>> numbers[::4]
[1, 5, 9]
步长不能为0，否则无法向前移动，但可以为负数，即从右向左提取元素
>>> numbers[8:3:-1]
[9, 8, 7, 6, 5]
>>> numbers[10:0:-2]
[10, 8, 6, 4, 2]
>>> numbers[0:10:-2]
[]
>>> numbers[::-2]
[10, 8, 6, 4, 2]
>>> numbers[5::-2]
[6, 4, 2]
>>> numbers[:5:-2]
[10, 8]
相加
>>> [1, 2, 3] + [4, 5, 6]
[1, 2, 3, 4, 5, 6]
>>> 'Hello,' + 'world!'
'Hello, world!'
>>> [1, 2, 3] + 'world!'
Traceback (innermost last):
File "<pyshell>", line 1, in ?
[1, 2, 3] + 'world!'
TypeError: can only concatenate list (not "string") to list
乘法
>>> sequence = [None] * 10
>>> sequence
[None, None, None, None, None, None, None, None, None, None]
[],[0],[None]都表示空序列
成员资格
>>> permissions = 'rw'
>>> 'w' in permissions
True
>>> 'x' in permissions
False
>>> users = ['mlh', 'foo', 'bar']
>>> input('Enter your user name: ') in users
Enter your user name: mlh
True
>>> subject = '$$$ Get rich now!!! $$$'
>>> '$$$' in subject
True
长度，最小值和最大值
>>> numbers = [100, 34, 678]
>>> len(numbers)
3
>>> max(numbers)
678
>>> min(numbers)
34
>>> max(2, 3)
3