Python中的序列包括，字符串、列表、元组。本文介绍序列的通用操作。

1. 切片中的None

>>> s = 'abcdefg'

>>> for i in range(-1, -len(s), -1):

...     print s[:i]

...

abcdef

abcde

abcd

abc

ab

a

>>> for i in [None] + range(-1, -len(s), -1):

...     print s[:i]

...

abcdefg

abcdef

abcde

abcd

abc

ab

a

>>> s[::-1]

'gfedcba'

>>> 

2. 类型转换

• list(iter)
• str(obj)
• unicode(obj)
• basestring()
• tuple(iter)

3. 序列内建函数

• enumerate(iter)
• len(seq)
• max(iter, key=None)
• max(arg0, arg1,…,key=None)
• min(iter, key=None)
• min(arg0, arg1,…,key=None)
• reversed(seq)
• sorted(iter, func=None, key=None, reverse=False)
• sum(seq, init=0)
• zip([it0, it1,…,itN])

>>> for i in enumerate(s):

...     print i

...

(0, 'a')

(1, 'b')

(2, 'c')

(3, 'd')

(4, 'e')

(5, 'f')

(6, 'g')

>>> len(s)

7

>>> max(s)

'g'

>>> min(s)

'a'

>>> for i in reversed(s):

...     print i

...

g

f

e

d

c

b

a

>>> sorted(s, reverse=True)

['g', 'f', 'e', 'd', 'c', 'b', 'a']

>>> l = range(7)

>>> l

[0, 1, 2, 3, 4, 5, 6]

>>> sum(l)

21

>>> zip(s,l)

[('a', 0), ('b', 1), ('c', 2), ('d', 3), ('e', 4), ('f', 5), ('g', 6)]

>>>