Python字符串拼接、截取及替换方法总结分析
本文实例讲述了Python字符串拼接、截取及替换方法。分享给大家供大家参考，具体如下：
python字符串连接
python字符串连接有几种方法，我开始用的第一个方法效率是最低的，后来看了书以后就用了后面的2种效率高的方法，跟大家分享一下。
先介绍下效率比较低的方法：
a = ['a','b','c','d'] content = '' for i in a: content = content + i print content
content的结果是:'abcd'
后来我看了书以后，发现书上说的是python连接字符串，特别是在循环连接字符串的时候，他每次连接一次，就要重新开辟空间，然后把字符串连接起来，再放入新的空间，再一次循环，又要开辟新的空间，把字符串连接起来放入新的空间，如此反复，内存操作比较频繁，每次都要计算内存空间，然后开辟内存空间，再释放内存空间，效率非常低，你也许操作比较少的数据的时候看不出来，感觉影响不大，但是你碰到操作数据量比较多的时候，这个方法就要退休了，还是看看下面2个比较先进的方法把。
先进方法1：
用字符串的join方法：
a = ['a','b','c','d'] content = '' content = ''.join(a) print content
content的结果:'abcd'
先进方法2：
用字符串的替换占位符替换
a = ['a','b','c','d'] content = '' content = '%s%s%s%s' % tuple(a) print content
content的结果是:'abcd'
有兴趣可以看看关于python字符串有关的 python 字符串替换 和 python 字符串截取
字符串截取
python的字符串是有序集合，我们可以通过索引来提取想要获取的字符，可以把python的字符串也做为字符串的列表就更好理解。
python的字串列表有2种取值顺序
1.是从左到右索引默认0开始的，最大范围是字符串长度少1
s = 'ilovepython'
s[0]的结果是i
2.是从右到左索引默认-1开始的，最大范围是字符串开头
s = 'ilovepython'
s[-1]的结果是n
上面这个是取得一个字符，如果你的实际要取得一断字符的话，可以用到python 字符串截取功能
比如:s = 'ilovepython'
s[1:5]的结果是love
当使用以冒号分隔的字符串，python返回一个新的对象，结果包含了以这对偏移标识的连续的内容，左边的开始是包含了下边界，比如上面的结果包含了s[1]的值l，而取到的最大范围不包括上边界，就是s[5]的值p
字符串替换
python 字符串替换是python操作字符串的时候经常会碰到的问题，这里简单介绍下字符串替换方法。
python 字符串替换可以用2种方法实现:
1.用字符串本身的replace方法
a.replace('word','python')
输出的结果是hello python
2.用正则表达式来完成替换:
import re
strinfo = re.compile('word')
b = strinfo.sub('python',a)
print b
输出的结果也是hello python
更多关于Python相关内容感兴趣的读者可查看本站专题：《Python字符串操作技巧汇总》、《Python入门与进阶经典教程》及《Python文件与目录操作技巧汇总》
希望本文所述对大家Python程序设计有所帮助。
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