62 lines
2.0 KiB
Python
62 lines
2.0 KiB
Python
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#!/usr/bin/env python
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# -*- encoding: utf-8 -*-
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"""
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Topic: 正则式分组替换示例
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"""
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import re
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class Nth(object):
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"""
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如果 sub 函数的第二个参数是个函数，则每次匹配到的时候都会执行这个函数。
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函数接受匹配到的那个 match object 作为参数，返回用来替换的字符串。
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利用这个特性就可以只在第 N 次匹配的时候返回要替换成的字符串，其他时候原样返回不做替换即可。
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"""
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def __init__(self, nth, replacement):
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self.nth = nth
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self.replacement = replacement
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self.calls = 0
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def __call__(self, matchobj):
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self.calls += 1
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if self.calls == self.nth:
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return self.replacement
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return matchobj.group(0)
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def re_sub():
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a = re.sub(r'(foo)(bar)', r'\g<1>123\g<2>', 'foobar')
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print(a)
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a = re.sub('a', 'A', 'abcasd') # 找到a用A替换，后面见和group的配合使用
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pat = re.compile('a')
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b = pat.sub('A', 'abcasd')
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print(b)
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# 通过组进行更新替换：
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pat = re.compile(r'(www\.)(.*)(\..{3})') # 正则表达式
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print(pat.match('www.dxy.com').group(2))
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# 通过正则匹配找到符合规则的”www.dxy.com“ ，取得组2字符串，用baidu替换之
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print('-----------')
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print(pat.sub(r'\g<1>baidu\g<3>', 'hello,www.dxy.com'))
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pat = re.compile(r'(\w+) (\w+)')
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s = 'hello world ! hello hz !'
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pat.findall('hello world ! hello hz !')
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# [('hello', 'world'), ('hello', 'hz')]
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# 通过正则得到组1(hello)，组2(world)，再通过sub去替换。即组1替换组2，组2替换组1，调换位置。
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print(pat.sub(r'\2 \1', s))
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# 替换字符串中第3个出现的good
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pat = re.compile(r'(good)')
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a = pat.sub(Nth(3, 'bad'), 'This is a good story, good is good. Oh, good')
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print(a)
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# 传入一个lambda函数，在匹配处两边加双引号
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a = pat.sub(lambda mo: '"' + mo.group(0) + '"', 'This is a good story, good is ')
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print(a)
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if __name__ == '__main__':
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re_sub()
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