re.match()
re.match 尝试从字符串的起始位置匹配一个模式，如果匹配失败，match()返回none
re.match(pattern, string, flags=0)
最常规的匹配
import re
content = 'Hello 11223 44445 World_This is Regex Demo'
result = re.match('^Hello\s\d\d\d\d\d\s\d{5}\s\w{10}.*Demo$', content)
print(result)
print(result.group())
print(result.span())
<_sre.SRE_Match object; span=(0, 42), match='Hello 11223 44445 World_This is Regex Demo'>
Hello 11223 44445 World_This is Regex Demo
(0, 42)
泛匹配
import re
content = 'Hello 11223 44445 World_This is Regex Demo'
result = re.match('^Hello.*Demo$', content)
print(result)
print(result.group())
print(result.span())
<_sre.SRE_Match object; span=(0, 42), match='Hello 11223 44445 World_This is Regex Demo'>
Hello 11223 44445 World_This is Regex Demo
(0, 42)
匹配目标
import re
content = 'Hello 11223 44445 World_This is Regex Demo'
result = re.match('^Hello\s(\d+).*Demo$', content)
print(result)
print(result.group(1))
print(result.span())
<_sre.SRE_Match object; span=(0, 42), match='Hello 11223 44445 World_This is Regex Demo'>
11223
(0, 42)
贪婪匹配
.* 会匹配尽可能多的字符
import re
content = 'Hello 11223 44445 World_This is Regex Demo'
result = re.match('^Hello.*(\d+).*Demo$', content)
print(result)
print(result.group(1))
print(result.span())
<_sre.SRE_Match object; span=(0, 42), match='Hello 11223 44445 World_This is Regex Demo'>
5
(0, 42)
非贪婪匹配
.*? 匹配尽可能少的字符
这里，它匹配到第一个数字就停止了
这样就达到我们想取出第一串数字的目的了
import re
content = 'Hello 11223 44445 World_This is Regex Demo'
result = re.match('^Hello.*?(\d+).*Demo$', content)
print(result)
print(result.group(1))
print(result.span())
<_sre.SRE_Match object; span=(0, 42), match='Hello 11223 44445 World_This is Regex Demo'>
11223
(0, 42)
匹配模式
import re
content = '''Hello 11223 44445 World_This
is Regex Demo
'''
result = re.match('^Hel.*?(\d+).*?Demo$', content, re.S)
print(result)
print(result.group(1))
<_sre.SRE_Match object; span=(0, 43), match='Hello 11223 44445 World_This \nis Regex Demo'>
11223
我们添加re.S是为了给.的匹配模式扩展到整个字符串，包括\n换行符
转义
import re
content = 'price is $5.00'
result = re.match('price is \$5\.00', content)
print(result)
<_sre.SRE_Match object; span=(0, 14), match='price is $5.00'>
可以使用反斜杠进行转义
小结：尽量使用泛匹配，使用括号得到匹配目标，尽量使用非贪婪模式，有换行符要用re.S
re.search()
re.search 扫描整个字符串并返回第一个成功匹配的字符
import re
content = 'hei, stt Hello 11223 World_This is Regex Demo'
result = re.search('Hello.*?(\d+).*Demo', content)
print(result)
print(result.group(1))
print(result.span())
<_sre.SRE_Match object; span=(9, 51), match='Hello 11223 44445 World_This is Regex Demo'>
11223
(9, 51)
小结：因为match会限制字符串头部，所以能用search就不用match
re.findall()
re.findall 扫描整个字符串并返回所有匹配的字符
import re
content = '''
<div class="info">
<div class="more-meta">
<h4 class="title">
邻人之妻
</h4>
<p>
<span class="author">
[美] 盖伊·特立斯
</span>
<span class="publisher">
上海人民出版社
</span>
</p>
</div>
</div>
<div class="info">
<div class="more-meta">
<h4 class="title">
深蓝的故事
</h4>
<p>
<span class="author">
深蓝
</span>
<span class="publisher">
新星出版社
</span>
</p>
</div>
</div>
'''
results = re.findall('"title">(.*?)</h4>.*?"author">(.*?)</span>.*?"publisher">(.*?)</span>', content, re.S)
for result in results:
title, author, publisher = result
print('title:', title.strip())
print('author:', author.strip())
print('publisher:', publisher.strip())
title: 邻人之妻
author: [美] 盖伊·特立斯
publisher: 上海人民出版社
title: 深蓝的故事
author: 深蓝
publisher: 新星出版社
re.sub()
re.sub 替换字符串中每一个匹配的子串后返回替换后的整个字符串
import re
content = 'hei, stt Hello 12345 World_This is Regex Demo'
content = re.sub('\d+', 'str', content)
print(content)
hei, stt Hello str World_This is Regex Demo
如果我们要替换的字符串包含它本身，我们可以给它用小括号分组，然后用反斜杠数字来引用
import re
content = 'hei, stt Hello 12345 World_This is Regex Demo'
content = re.sub('(\d+)', r'\1 678910', content)
print(content)
hei, stt Hello 12345 678910 World_This is Regex Demo
re.compile()
re.compile 将正则表达式编译成正则对象
只需要一次编译，就可以达到反复使用
import re
content = '''hei, stt Hello 12345 World_This
is Regex Demo'''
pattern = re.compile('h.*?Demo', re.S)
result = pattern.match(content)
print(result)
<_sre.SRE_Match object; span=(0, 46), match='hei, stt Hello 12345 World_This \nis Regex Demo'>
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