Python-2-序列及通用序列操作

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]

'http://www.python.org'

>>> 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