学步园

代码如下：

#encoding=utf-8


print '中国'


#访问子字符串


#方案一 切片  一次只能取一个
print '------1'
str ='abc中国'
ustr =u'abc中国'


print str[2:6] #相当于2-5 中文占了2个 因为是UTF-8
print ustr[2:4] #unicode


#方案二 struct.unpack 考虑长度
print '-----2'
import struct
theline='abcd12345678901234567890jklm'


baseformat = '5s 3x 8s 8s'
remain = len(theline) - struct.calcsize(baseformat)
print remain


format = '%s %ds'%(baseformat,remain)
 
print format
l,s1,s2,t= struct.unpack(format, theline)


print l
print s1
print s2
print t


l,s1,s2 = struct.unpack(baseformat,theline[:struct.calcsize(baseformat)])


print l
print s1
print s2


#方案三 列表推导方法 n个字节一组
print '------3'
n = 5
print [theline[k:k+5] for k in xrange(0,len(theline),5)] #xrang 0开始len(theline)结束 步长为5


#切割为一个数组
chars =list(theline)
print chars


#方案四 切割成指定长度
print '------4'
cuts = [8,14,20,26,27]
pieces = [theline[i:j] for i,j in zip([0]+cuts,cuts+[None])]


print pieces


#封装 一 unpack
def fields(baseformat,theline,lastfiled=False):
    remain = len(theline) - struct.calcsize(baseformat)
    format = '%s %ds'%(baseformat,remain,lastfiled and 's' or 'x')
    return struct.unpack(format,theline)


#封装三 slices 等长
def fields1(theline,n,lastfiled=False):
    pieces = [theline[k:k+n] for k in xrange(0,len(theline),5)] 
    if not lastfiled or len(pieces[-1]) < n:
        pieces.pop()
    return pieces


#封装 一 slices 变长
def fields2(theline,cuts,lastfiled=False):
    pieces = [theline[i:j] for i,j in zip([0]+cuts,cuts+[None])] 
    if not lastfiled:
        pieces.pop()
    return pieces


#study zip
print [0]+[1,2]
print [5]+[6,7]
print zip([0]+[1,2],[5]+[6,7])

运行结果如下：

中国
------1
c中
c中
-----2
4
5s 3x 8s 8s 4s
abcd1
56789012
34567890
jklm
abcd1
56789012
34567890
------3
['abcd1', '23456', '78901', '23456', '7890j', 'klm']
['a', 'b', 'c', 'd', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'j', 'k', 'l', 'm']
------4
['abcd1234', '567890', '123456', '7890jk', 'l', 'm']
[0, 1, 2]
[5, 6, 7]
[(0, 5), (1, 6), (2, 7)]