Python序列——序列操作

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]... abcdefabcdeabcdabcaba>>> for i in [None] + range(-1, -len(s), -1):...     print s[:i]... abcdefgabcdefabcdeabcdabcaba>>> 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... gfedcba>>> 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)]>>>